Investigation: Was my PCM reprogrammed?

[MAC]

Back in October 2010, GM sent a letter to owners advising that they have decided to extend the catalytic converter warranty until either 200,000 miles or 12 years, whichever occurs first. I posted about this in CaddyInfo's STS forum. Owners who suspect a faulty converter(s) are instructed to bring the vehicle to a Cadillac dealership for diagnosis. If the dealership determines there is a defective converter, it will be replaced free of charge.

It just so happens that I was one of the unlucky owners who ended up with a faulty catalytic converter, which I was able to diagnose by using my scantool and ScanXL (standard) software. I did the research after reading the codes and suspected one of the catalytic converters was faulty. Accordingly, I brought my STS to a Cadillac dealership where it was diagnosed as having two faulty catalytic converters. So I made an appointment and had them replaced under the extended warranty. I was told by the service department that it was determined that both catalytic converters needed to be replaced. However, I'm thinking there is a possibility that they were not actually replaced.

Let me explain: After they were supposedly replaced, I happened to be in a position to take a look at them while replacing my front brakes. I, of course, jacked the front end up and I decided to take the opportunity to look at the converters which are mounted on the exhaust pipes/exhaust manifolds. What struck me is that they were rusted and looked just like my originals when I inspected them several months earlier. I became immediately suspicious because they were suppose to be only months old in light of the fact that the Cadillac dealership said they were both replaced under the extended warranty. So I became suspicious that maybe they weren't replaced after all and the dealership technicians did a work-around instead.

This evening I decided to use my OBDLink (WiFi) and ScanXL software to find out why my check engine light is on, which has been on for a while. I found multiple codes including both oxygen sensor banks not functioning correctly, ECM code, and both camshaft position sensor codes. I cleared the codes and none of them returned (so far) after I did a quick test drive to see if they would reset. I know that chances are they will reset unless they were caused by a freak situation. I then turned to checking the oxygen sensors. I noticed that although ScanXL detects that both are "present"; however, ScanXL is not detecting any numerical figures associated with oxygen sensor data, as none show up in the results colums. All I see are dashes in the columns. Again, before I brought my STS to the dealer, I scanned the oxygen sensors and found that, at that time, ScanXL was reading and providing oxygen sensor data. This evening, after I cleared the trouble codes, I again used ScanXL to take a look at the oxygen sensors and again found no data was being read via either oxygen sensor; however, both oxygen sensors were detected as "present".

Question:

Is it possible the dealer reprogrammed the Powertrain Control Module (PCM) in some way to shut down the ability of the PCM to read data and therefore not set off catalytic converter trouble codes? In other words, is it possible the dealer shut down the ability of the PCM to transmit and/or read oxygen sensor data in order to prevent the PCM from setting off the dreaded P0420 code? There was one more code that set dealing with the converters?

(Please note that I am not making any accusations in this post. I am merely seeking input as to the possibilities. There are many knowledgeable members of CaddyInfo who may be in a position to provide input as to the possibilities)

[Bruce Nunnally]

When people want to run with no cats they get o2 bypass gadgets, or o2 bypass simulators, which give a 'constant good' signal, thus avoiding a catalytic converter malfunction light.

It is also possible that the new cats used are not stainless steel, and simply began to rust from day one I suppose.

[Cadillac Jim]

The ScanXL data is a real killer here; I think it nails the fact that you HO2 sensors are dummies. I would *hope* that the ones on the exhaust manifold are OK because otherwise your fuel injection is running open loop. If you don't have the original repair invoice, I would stop by and ask them to print out another one for you.

I would find another dealer, at least 30 miles away, and have them look at it. Select them for the size of the service department - large service departments can't sustain an undetected clique of crooks for very long. A huge service department in an auto mall that services all GM makes is good; that worked for me. Don't be afraid to tell them that you took it into another dealer for cat replacement and now your HO2 sensors seem to be dummies according to your scan tool, and your cats don't seem to have been changed.

You don't need to call GM Customer Service unless you get the runaround at the second, and third, dealer that you try. The dealer that fixes the car will likely set the red flag for GM, intentionally or unintentionally. "Replaced dummy HO2 sensors and bad cats" as a repair procedure will raise huge flags in the GM service review process.

When I had my 1990 Pontiac Grand AM GT with the Quad 4 HO, I had a mechanic at a Pontiac dealer in Atlanta tell me that I had a cracked head. I rolled my eyes up because there were no symptoms - I was in for routine periodic service - and they did the job, or so we were told by the tech. When I got home, I looked, and the head had not been changed. I knew through the grapevine that this tech built engines at home, and that one of them was a Quad 4 HO project. A few months later when I came back for another periodic service, he wasn't there anymore. It happens. I didn't say anything because the dealer handled it.

Catalytic converters are worth a lot of money in the recycling trade. Since the work was done at a GM dealer, the VIN will bring up the work in the service department's computer, and you should have no problem with the warranty. I think that you have no choice but to fix this because eventually your car won't pass an emissions check that includes a tailpipe sniffer.

[Texas Jim]

With the right software the O2 sensors are able to be TURNED OFF...

They are still there and will show "PRESENT" but are not putting out data...

Guys that put long tube headers on GM trucks have issues with the O2 sensors not getting hot enough, and either have to put in dummies, that always give the right signal or just turn off the O2 sensors.

I think I would do as Jim suggested above... take it to another dealer and explain everything and see what they come up with.

Also... if you know and trust someone at a "GOOD" muffler shop... yo might run it by there and ask them to look at it and see if you have new cats...

Here is sort of an example of what I was talking about....

http://www.truckmodcentral.com/forums/showthread.php?t=19447

[Cadillac Jim]

I didn't address your original question, about reprogramming the PCM. The PCM memory comes in three types: RAM, which is not programmable but must be changed with the PCM, EEPROM, which is set and changed by the programs in the PCM and which stays when the battery is disconnected, and RAM, which is just slush space with data that goes away when the battery is disconnected but that most program need scads of to run.

That said, the things that constitute OBD compliance with be in RAM and not changeable. I believe that's part of the OBD compliance, to not have the compliance parameters and code changeable in a product delivered to the public. So, no, they didn't reprogram you PCM. Reprogramming the PCM is limited to changing parameters available in EEPROM.

[MAC]

The ScanXL data is a real killer here; I think it nails the fact that you HO2 sensors are dummies. I would *hope* that the ones on the exhaust manifold are OK because otherwise your fuel injection is running open loop. If you don't have the original repair invoice, I would stop by and ask them to print out another one for you.

I would find another dealer, at least 30 miles away, and have them look at it. Select them for the size of the service department - large service departments can't sustain an undetected clique of crooks for very long. A huge service department in an auto mall that services all GM makes is good; that worked for me. Don't be afraid to tell them that you took it into another dealer for cat replacement and now your HO2 sensors seem to be dummies according to your scan tool, and your cats don't seem to have been changed.

You don't need to call GM Customer Service unless you get the runaround at the second, and third, dealer that you try. The dealer that fixes the car will likely set the red flag for GM, intentionally or unintentionally. "Replaced dummy HO2 sensors and bad cats" as a repair procedure will raise huge flags in the GM service review process.

When I had my 1990 Pontiac Grand AM GT with the Quad 4 HO, I had a mechanic at a Pontiac dealer in Atlanta tell me that I had a cracked head. I rolled my eyes up because there were no symptoms - I was in for routine periodic service - and they did the job, or so we were told by the tech. When I got home, I looked, and the head had not been changed. I knew through the grapevine that this tech built engines at home, and that one of them was a Quad 4 HO project. A few months later when I came back for another periodic service, he wasn't there anymore. It happens. I didn't say anything because the dealer handled it.

Catalytic converters are worth a lot of money in the recycling trade. Since the work was done at a GM dealer, the VIN will bring up the work in the service department's computer, and you should have no problem with the warranty. I think that you have no choice but to fix this because eventually your car won't pass an emissions check that includes a tailpipe sniffer.

Thanks for the input, Jim. I'm concerned that if I bring the STS to another Cadillac dealer its service department may try to coverup any tampering. I would think that Cadillac dealerships would tend to stick together. If I explain to a second dealer that I suspect the converters were not replaced, I'm doubtful it would want to be put in a situation where it may jeopardize another dealership or it may contact the first dealership and try to figure a way out by doing something to coverup and/or lie and tell me that I don't know what I'm talking about. From what I understand, tampering with an automobile's emissions system is a federal offense, which would be the case if the dealership turned off oxygen sensors and/or installed dummy sensors. I'm not sure a second dealer would want to get involved? Don't get me wrong, I would certainly like to get confirmation of any tampering from a second dealer.

[Texas Jim]

Go to a good independent muffler shop and ask to have the cats checked...

Don't tell them any history of what may or may not have happened at the dealer...

See what they have to say about them...

[Cadillac Jim]

Cadillac and just about all other car dealers that I know of in the USA are independent franchisees, and although there is some courtesy between them, if you go far enough away - that's why I said at least 30 miles - they will have no connection and no feelings for a dealer in the next town or two over. They may or may not turn them in depending on mandatory reporting regulations. Here's what the service manager and service representative will see when you come in:

A Cadillac owner with a six-year-old STS comes in with a complaint about cat performance. Customer states that replacement of cats was apparently done in October 2010 but customer's visual inspection shows that they seem not to have been changed. Oxygen sensors on cat seem to be dummies according to customer's scan tool.

Now, look at this from all the points of view that we have here.

DEALER SERVICE: An almost self-diagnosing, very simple to verify complaint. Straight parts replacement under extended GM cat warranty. Good money, quick job, and an almost certainly satisfied customer.

CADILLAC DEALER: We have a PR disaster waiting to happen here. We can make it right in a couple of hours.

LAW ENFORCEMENT: Customer comes in with bad cat complaint, we *must* fix it. If there has been fraud, we *must* report it.

Unless your second dealer is owned by the brother-in-law of the first dealer, you won't have a problem. In fact, if you went back to the very same dealer with this complaint and sat down in the service manager's office, you still have a very good chance of getting your car fixed for free without question. Why? My thinking is that a single tech decided to steal your new cats for the salvage cost and cover it up with dummy oxygen sensors and that he is long gone, either fired or quit without forwarding address before the worthless substance encountered the rotary circulation device, and that the dealer will gratefully fix the problem and make everything right and keep everything close. The idea that the whole dealership including management is part of the problem is unthinkable, particularly in the light of GM's recent deep culling of all dealerships, particularly Cadillac dealerships. The worst thing that can happen is that they don't "get it" and just give the car to the same tech, and you can simply insist that this does not happen.

But, the simplest and safest thing for you to do is to go on the Cadillac web site, put your ZIP code in the dealer locator, and pick a dealer with a big service department that is the other direction from (or in any case not anywhere near) the dealer that futzed your cat and oxygen sensors and just have it fixed on warranty - again. You will have almost zero risk and the bad tech will be busted anyway, it will just take a few days longer.

[MAC]

Go to a good independent muffler shop and ask to have the cats checked...

Don't tell them any history of what may or may not have happened at the dealer...

See what they have to say about them...

I'm seriously thinking about contacting the Environmental Protection Agency (EPA) since it is the agency that monitors compliance with the Clean Air Act and compliance with motor vehicle emission standards. I would want to know if there is anything I should do in particular if I suspect emissions system tampering.

Here is a link to the EPA's complaint form.

[MAC]

Cadillac and just about all other car dealers that I know of in the USA are independent franchisees, and although there is some courtesy between them, if you go far enough away - that's why I said at least 30 miles - they will have no connection and no feelings for a dealer in the next town or two over. They may or may not turn them in depending on mandatory reporting regulations. Here's what the service manager and service representative will see when you come in:

A Cadillac owner with a six-year-old STS comes in with a complaint about cat performance. Customer states that replacement of cats was apparently done in October 2010 but customer's visual inspection shows that they seem not to have been changed. Oxygen sensors on cat seem to be dummies according to customer's scan tool.

Now, look at this from all the points of view that we have here.

DEALER SERVICE: An almost self-diagnosing, very simple to verify complaint. Straight parts replacement under extended GM cat warranty. Good money, quick job, and an almost certainly satisfied customer.

CADILLAC DEALER: We have a PR disaster waiting to happen here. We can make it right in a couple of hours.

LAW ENFORCEMENT: Customer comes in with bad cat complaint, we *must* fix it. If there has been fraud, we *must* report it.

Unless your second dealer is owned by the brother-in-law of the first dealer, you won't have a problem. In fact, if you went back to the very same dealer with this complaint and sat down in the service manager's office, you still have a very good chance of getting your car fixed for free without question. Why? My thinking is that a single tech decided to steal your new cats for the salvage cost and cover it up with dummy oxygen sensors and that he is long gone, either fired or quit without forwarding address before the worthless substance encountered the rotary circulation device, and that the dealer will gratefully fix the problem and make everything right and keep everything close. The idea that the whole dealership including management is part of the problem is unthinkable, particularly in the light of GM's recent deep culling of all dealerships, particularly Cadillac dealerships. The worst thing that can happen is that they don't "get it" and just give the car to the same tech, and you can simply insist that this does not happen.

But, the simplest and safest thing for you to do is to go on the Cadillac web site, put your ZIP code in the dealer locator, and pick a dealer with a big service department that is the other direction from (or in any case not anywhere near) the dealer that futzed your cat and oxygen sensors and just have it fixed on warranty - again. You will have almost zero risk and the bad tech will be busted anyway, it will just take a few days longer.

I understand your point of view. Assuming the cats were not replaced, I tend to agree with you that it's very unlikely management is involved. Then again, I'm also not willing to brush aside the possibility. I'm pretty positive the cats were not replaced--though I also don't want to throw around accusations that turn out to be unfounded.

So let's say I go to another Cadillac dealership, what should I say? I know of one that is more than 30 miles away, which I have been to in the past. How about I simply ask them to do an emissions test because I want to know if my car will pass inspection? My main concern is that I want the testing to focus on the O2 sensors so the dealership will see the sensors are not providing any data. Chances are the dealership will input my VIN # and find out that I had the catalytic converters replaced.

[Cadillac Jim]

I would just tell them the truth, that you went to another dealer with a bad cat late last year and that you gradually realized that the car wasn't fixed, that the cat looks like the old one, and that you have a very good scan tool that tells you that the oxygen sensors on the cat are dummies. You must keep emotion out of it to succeed at something like this. That removes all doubt about your intelligence and veracity. And it puts the weight of the laws on emissions to fix the problem on the service department.

If you go to an independent muffler shop, you can kiss your GM warranty goodbye. That's not as bad as it sounds, because an aftermarket cat is only a little over $100 and they rarely go bad unless physically damaged or you have a severe engine problem and you drive it that way. But you can get your car fixed for free and keep the GM warranty with just a little faith and honesty.

If, after explaining your complaint to the service manager (not just the service representative, but his boss), if you are at all uncomfortable just drive away and go to another dealer. If you strike out at two, then call GM Customer Service. And tell them you want your car fixed at a *third* service department that *they* vouch for, or you want to meet a factory GM representative at a dealer with your car. I would call GM first because if you call the law first, then GM won't likely want to talk to you until the litigation is settled.

You might print out a web page of someone that sells dummy oxygen sensors, just to show the shop manager that such a thing exists. I never heard of such a thing and my first reflex it that they would be illegal to make or sell anywhere. The case on the web page at the link someone gave above, that they are useful for off-road use, seems weak to me because no one cares if the MIL light is on when you are running a quarter-mile or whatever. In any case you will always have a code, "Not Ready" OBD status, no waveforms on the oxygen sensors on the cat (they have a whole tab for that function in ScanXL) and such, which I'm sure you already know.

[MAC]

With the right software the O2 sensors are able to be TURNED OFF...

They are still there and will show "PRESENT" but are not putting out data...

Guys that put long tube headers on GM trucks have issues with the O2 sensors not getting hot enough, and either have to put in dummies, that always give the right signal or just turn off the O2 sensors.

I think I would do as Jim suggested above... take it to another dealer and explain everything and see what they come up with.

Also... if you know and trust someone at a "GOOD" muffler shop... yo might run it by there and ask them to look at it and see if you have new cats...

Here is sort of an example of what I was talking about....

http://www.truckmodcentral.com/forums/showthread.php?t=19447

Hi Jim,

Thanks for the input. Do you know as a fact that oxygen sensors can be turned off or is it something you've heard? My first guess when I saw that not data was being transmitted from the O2 sensors is that they where possibly disabled through the PCM.

[MAC]

I would just tell them the truth, that you went to another dealer with a bad cat late last year and that you gradually realized that the car wasn't fixed, that the cat looks like the old one, and that you have a very good scan tool that tells you that the oxygen sensors on the cat are dummies. You must keep emotion out of it to succeed at something like this. That removes all doubt about your intelligence and veracity. And it puts the weight of the laws on emissions to fix the problem on the service department.

If you go to an independent muffler shop, you can kiss your GM warranty goodbye. That's not as bad as it sounds, because an aftermarket cat is only a little over $100 and they rarely go bad unless physically damaged or you have a severe engine problem and you drive it that way. But you can get your car fixed for free and keep the GM warranty with just a little faith and honesty.

If, after explaining your complaint to the service manager (not just the service representative, but his boss), if you are at all uncomfortable just drive away and go to another dealer. If you strike out at two, then call GM Customer Service. And tell them you want your car fixed at a *third* service department that *they* vouch for, or you want to meet a factory GM representative at a dealer with your car. I would call GM first because if you call the law first, then GM won't likely want to talk to you until the litigation is settled.

You might print out a web page of someone that sells dummy oxygen sensors, just to show the shop manager that such a thing exists. I never heard of such a thing and my first reflex it that they would be illegal to make or sell anywhere. The case on the web page at the link someone gave above, that they are useful for off-road use, seems weak to me because no one cares if the MIL light is on when you are running a quarter-mile or whatever. In any case you will always have a code, "Not Ready" OBD status, no waveforms on the oxygen sensors on the cat (they have a whole tab for that function in ScanXL) and such, which I'm sure you already know.

I'm going to try to make an appointment with another Cadillac dealership. I think I'll ask to speak to the head manager of the entire dealership so I can explain the situation and gauge the response. If I'm given a run-around or a 'Well...Uhm..." routine, then I will move on to another dealership.

[MAC]

I just spoke with another Cadillac dealership for a good 10 minutes and was essentially told (and I’m paraphrasing):

1) It’s highly unlikely that any reprogramming of the PCM would remain for almost a year. In other words, the PCM would eventually override the reprogramming that shut off O2 sensors (for example) and accordingly, if the cats were not replaced, the cat codes would reappear;

2) When work is performed under warranty, GM requires dealerships to send replaced part(s) to GM to confirm the work was needed and as part of the reimbursement process and may use them for testing purposes. Therefore, it is unlikely a dealership would not replace catalytic converters because same must be sent to GM.

3) I was advised that all the dealership will do is check for codes, which means it will not do anything to determine if the PCM has been reprogrammed, assuming same is possible.

4) Interestingly, I was also told that there is nothing a person can do to trick the PCM or by pass the O2 sensors. I refuted this idea by saying that I am aware that people use spark plug spacers to try to bypass the sensors. I was not refuted by the service department rep when I said this, which tells me she was either not knowledgeable enough to confirm or refute it or she didn’t believe I would know about this tactic and didn’t want to admit it’s possible to use a spark plug anti-fouler spacer to bypass an O2 sensor.

5) I will not be taking my STS to this second dealership because I do not feel it will try to address my concerns in a serious way to confirm or refute my belief that my cats may have not been replaced.

At this point, I’m thinking that I should take my STS to s NJ inspection station and explain the situation and see if they are willing and able to perform an emission test so I can find out if the emissions system has been compromised in any way that makes emissions testing impossible and whether there is an emissions problem.

Also, I may try to contact GM to see if there is a record of the job number on my receipt.

[Cadillac Jim]

MAC, print out the web page that offers dummy oxygen sensors for sale and bring it with you. That will solve the problem of the service people not believing you when you say that the oxygen sensors are dummies.

I think you should forget the idea that the PCM was reprogrammed. That's really not possible in your model year, and the service manager seemed to have some fuzzy idea about that. It's pretty clear from your ScanXL data that the oxygen sensors are dummies and there is no evidence that the PCM itself was messed with, other than clearing the codes.

I agree that you shouldn't try that particular dealer again. Once a service representative has taken a position crossways with a customer, they are gone forever, usually, and you must change dealers. It doesn't matter what, or why.

I *do* think you should try one more dealer, then if that doesn't work out call GM Customer Relations. The number on the brass keyring disc for road service will do; they can transfer you from there. Then, if that doesn't work, do something that will bring in the law, like going to a NJ Inspection Station. Be warned, though, the NJ Inspection station may just scrape off your inspection sticker and turn a deaf ear to anything further. You will have to deal with whatever paper they give you, which may only state that your car failed emissions testing and nothing else, and a car with no inspection sticker.

This last time you try a dealer, I think its a good idea to focus on what you absolutely positively know to be true:

• The oxygen sensors are dummies according to your scan tool. If you can print out the page from ScanXL, do so and take it with you. Be *sure* to print out the web page that offers them for sale.
• The cat seems to be old. If you can, take a photo and print it out, and take that with you.
• Take the old dealer invoice from last November with you. If you don't have it, stop by and ask them to print out another for you. Tell them it's for a prospective buyer or some such if they as,.
• Run the OBD codes as they stand now and take the list with you. This is the clincher.

Good luck.

[airmike]

I personally would never take the car to an inspection station for fear they would decide your car was not ok and you couldn't continue to drive it. Or even decide it was needed for evidence! Maybe as a last resort, if I had another vehicle to drive just in case.

[MAC]

This weekend I'm going to inspect the O2 sensors to see if there are any obvious signs of tampering (i.e. a spark plug anti-fouling spacer). If a spacer was used, I should be able to see it. Also, from what I have read on the Internet, some people use tin foil to cover sensors. Since my OBD-II scanner is not able to read O2 sensor information and my cats do not look as new as they should for being less than a year old, which is when I inspected them, I am suspicious that they were not replaced. Actually, I pretty convinced something is wrong but I'm not willing to make direct accusations unless I have incontrovertible evidence. The converters are not new, which should be sufficient enough; however, since I did not inspect them immediately after they were supposed to be replaced, I cannot categorically say they are not new. I'm looking for one more piece of evidence.

[MAC]

I inspected the right side (passenger side) downstream O2 sensor and could find nothing indicating tampering. I removed the sensor and inspected it and found nothing unusual. I did not remove the left side sensor because after seeing the right side was good I didn't feel it was necessary. The only remaining thing that I would like to settle is whether it's possible to shutdown or reprogram the ECM or PCM in such a way that it would be possible to effect or interfere with monitoring the catalytic converters in such a way that no codes would set. Given my state of suspicion (as baseless as it may be), I think I'll bring my car to a garage and have the emissions tested to see if anything unusual is detected and whether my STS passes emissions.

[Texas Jim]

I inspected the right side (passenger side) downstream O2 sensor and could find nothing indicating tampering. I removed the sensor and inspected it and found nothing unusual. I did not remove the left side sensor because after seeing the right side was good I didn't feel it was necessary. The only remaining thing that I would like to settle is whether it's possible to shutdown or reprogram the ECM or PCM in such a way that it would be possible to effect or interfere with monitoring the catalytic converters in such a way that no codes would set. Given my state of suspicion (as baseless as it may be), I think I'll bring my car to a garage and have the emissions tested to see if anything unusual is detected and whether my STS passes emissions.

I do not know "FOR SURE" about your year model.

I have been told that the 2005 and older Cadillacs were very hard to change anything in the PCM.

Starting with the 2006 Cadillac, it is easy.

I have changed a LOT OF STUFF on my 2006 DTS... but I have tried to be careful and not mess up the emissions stuff.

In Texas we do have to pass emission testing.

[Cadillac Jim]

I think that the emissions laws require that the emissions-related code not be modifiable by customer or dealer.

I'm not sure whether you could tell by looking if an oxygen sensor had been modified. I checked the web site that sells them, and it looks like the only difference between an OEM oxygen sensor and a disabled one is that the sensing wafer in the dummy isn't made of the exotic stuff that makes volts when oxygen is detected.

I do think that when ScanXL sees no data, that the output of the oxygen sensors is a simple flat voltage, not a sensor output. You can verify this in ScanXL by looking at the oxygen sensor plots.

[Luke]

In Texas we do have to pass emission testing.

Only in the DFW area. :-)

[MAC]

I do not know "FOR SURE" about your year model.

I have been told that the 2005 and older Cadillacs were very hard to change anything in the PCM.

Starting with the 2006 Cadillac, it is easy.

I have changed a LOT OF STUFF on my 2006 DTS... but I have tried to be careful and not mess up the emissions stuff.

In Texas we do have to pass emission testing.

I posted at CadillacOwners.com asking, "Is it possible to disable downstream O2 sensors through ECM or PCM?" and was eventually told that dealerships can modify ECM parameters in order to avoid replacing catalytic converters. If you scan the thread you will notice it wasn't very pleasant. I was accused of soliciting information in order to commit a federal offense and accused of making accusations against the dealer. The thread ended up locked at one point but was reopened because I not only vehemently denied that I was looking to commit a federal offense but ended up PM the webmaster and the instigator, dkozloski. I was so upset I called dkozloski a few choice words in a PM and called the webmaster a jerk for closing the thread. I ended up starting a new thread just to deny the allegations against me because I was not given an opportunity to respond. It's a real circus over there as far as my particular thread.

I also happened to come across another discussion on this topic at FixYa and there is a post from an individual who also said dealerships can reprogram the ECM.

[Cadillac Jim]

The key is That the dealer may be able to reprogram some parameters that throw a code and turn on the MIL but they cannot disable the oxygen sensors.

As for flames and flamers, I always repeat this mantra when I'm tempted to respond to one: Never wrestle with a pig; you both get dirty and the pig likes it.

[MAC]

The key is That the dealer may be able to reprogram some parameters that throw a code and turn on the MIL but they cannot disable the oxygen sensors.

As for flames and flamers, I always repeat this mantra when I'm tempted to respond to one: Never wrestle with a pig; you both get dirty and the pig likes it.

Hi Jim,

Here is what one of the moderators of the forum said:

Jesda

Posts 18,295

Re: Is it possible to disable downstream O2 sensors through ECM or PCM?

You can "simulate" an O2 sensor with dummy units but the legality of that is uncertain. An O2 bypass isn't technically the removal of emissions hardware, it just gets around the monitoring by sending a false "OK" signal.

It is possible to bypass the O2 signal with an ECM modification, but that's typically an aftermarket thing for specific vehicles. The code has to be 'cracked' and there has to be enough aftermarket demand for someone to be motivated to do that. The STS is not a vehicle that typically appeals to people who do major performance modifications that require ECU remapping, and your dealer likely will not have access to something like that nor will they invest the time and energy into engineering it. They could reset your ECM or reflash it with GM-provided software, but resetting/reflashing is not the same as modifying.

If they simply cleared the error code, a CEL/fault code would return within 1-2 days of driving.

Link to post

The part that sticks out to me is the statement that a dealer can "bypass the O2 signal with an ECM modification". When I hooked up my OBDII scanner about a week ago it could not read data coming from either O2 sensor. But before going to the dealer to replace the converters both O2 sensors were putting out data. Perhaps there was a glitch and that if I try again I will see data? I will try again to see if the O2 sensors are putting out data just to make sure. Again, I'm not making any accusations because I would need confirmation the ECM's programming was modified, but this is an interesting statement nonetheless.

EDITED:

Even though I'm suspicious, I am very doubtful the dealership's techs would get involved with remapping the ECM to bypass the O2 sensors. This certainly doesn't sound like something GM would permit and would thus have to be done without GM's permission. If my ECM is reflashed to make sure its programming is according to original factory specs which, in turn, causes the P0420 and/or P0430 codes to set again and my scan tool is again able to read O2 sensor data, and I can get a printout of some sort showing changes were made to the ECM, then I would be willing to conclude the unthinkable.

[KHE]

Isn't there a date cpde somewhere on the catalytic converter? There should be and that would clear up part of the mystery.