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Understanding Fault Tree for E046 PCM Code


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Check the EGR tubes in the intake manifold below the throttle body blades. They might be clogged, just pen the tbody blades up and look down.

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Ok thanks, fellas.

I have a lot of work to do in the next week or two, I guess.

I will let you all know if I am able to get rid of the E046 code and also pass the smog test.

I think threads posted here are much more useful when we can read about how to successfully solve particular problems and trouble codes seen on the cars.

If the original posters just disappear at the end of a thread, we never know if a certain approach was successful or not.

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5 hours ago, area310dude said:

I think threads posted here are much more useful when we can read about how to successfully solve particular problems and trouble codes seen on the cars.

If the original posters just disappear at the end of a thread, we never know if a certain approach was successful or not.

WELL SAID !!!! TYVM

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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  • 3 months later...

Hi OldCadTech and Cadillac guys

It's been a long time since I last posted, but in that time I replaced both O2 sensors, the EGR valve, cleaned out the throttle body and EGR tubes, added fuel injector cleaner, but unfortunately the E046 'Left to Right Bank Fueling Difference' code came back just the same!

I think I did learn something that could be an important clue though.

When I removed the right bank O2 sensor, it was very black and sooty, but the old left bank O2 sensor was very clean looking, with no black stuff at all.  Obviously the right bank cylinders are combusting much richer than the lean left bank.

Maybe I should look for a non-working fuel injector(s) on the left bank, causing a lean condition?

Running too lean causes excessive NOx and smog test failures too, right?

 

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9 hours ago, area310dude said:

Maybe I should look for a non-working fuel injector(s) on the left bank, causing a lean condition?

Running too lean causes excessive NOx and smog test failures too, right?

Lean fuel mixtures cause high NOx. A lean fuel mixture exists when less fuel than required is delivered to the combustion chambers or when more air then necessary is added to the fuel.

Very distinct possibility of injector O-ring cracking and leaking, I'm thinking it is sucking TOO much air, BUT yes, a dirty or plugged injector will cause the same problem. To verify, spray carb cleaner or brake cleaner around the injectors and see if the rpm's rise. If the rpm rises change the injector o-rings.

Edited by OldCadTech

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Ok thanks, that sounds like an easy check, I'll try it.

 

I had another funny thought about the left/right bank fueling difference:

Since I haven't had a smog test yet to see if my NOx has reduced since cleaning the EGR system and replacing the EGR valve, could it be possible that the maybe the left bank is NOT TOO LEAN, but just fine?

Because maybe the right bank is burning TOO RICH, caused by a faulty injector on the right bank that is dripping extra fuel?

I included a picture of the old left and right O2 sensors below, can you conclude something from that?

And also, I should mention that the 'Service Engine Soon' light from the E046 code has always been intermittent, not constant, and always throwing the SES light when the engine is hot, usually when I get home after a long trip and the car is idling in the driveway.  The SES light is always off with E046 as a 'history' when I start it from a cold condition.  When the E046 code and 'Service Engine Soon' light comes on as 'current', I can also detect a faint rotten egg smell from the exhaust.  Isn't rotten egg smell an indicator of burning the fuel too rich?

Can we make some conclusions about these extra pieces of evidence I have provided?

IMG0478.jpg

Edited by area310dude
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The one on the left should look like the one on the right. The right one is slightly rich but probably because of the A/fuel ratio imbalance.

I would concentrate on the left side first.

You could, possibly, pass a DEQ test BUT I doubt it. I think the low speed test would do you in. But I've seen stranger things happen  at DEQ test stations.

12 hours ago, area310dude said:

I should mention that the 'Service Engine Soon' light from the E046 code has always been intermittent, not constant, and always throwing the SES light when the engine is hot, usually when I get home after a long trip and the car is idling in the driveway.  The SES light is always off with E046 as a 'history' when I start it from a cold condition. 

You won't get a current E046 on a cold start cuz the system has to be in closed loop.

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Hi

I'm delaying the O-ring carburetor spray test a bit until the fuel injector additive in my gas tank burns down a bit more.

In the meantime could you tell me what the values below might indicate in relation to my E046 dilemma?

These are the diagnostic values just at idle.  I figure any extra evidence to share with you might help solve the puzzle.

 

ED36 Left Fuel Integrator   128

ED37 Right Fuel Integrator  128

ED38 Left Block Learn Fuel   122

ED 39 Right Block Learn Fuel  104

 

The numbers tend to jump around a bit with the exception of the 104 Right B/L number that stays steady.

 

 

Edited by area310dude
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The fuel integrator is what the ECM is commanding.

The block learn is that the left bank is trying to enrich the mixture and the right bank is is trying to lean the fuel mixture. It is running off a  pre-programmed "block" of parameter information to perform that task.

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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I read in the FSM that 128 is the optimal value for codes ED36 thru ED39.

Since both the Left and Right B/Ls are below 128 (122 and 104 respectively) doesn't this indicate that both banks are too rich as sensed by the O2 sensors and they are trying to run lean?

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No, if you disconnect the battery, the BL adjustments default to 128 (the neutral value for BL is 128). 

Another name for BLOCK LEARN is long term fuel trim. There are more than one BL value, unlike the single Integrator. There is a table in the ECM EPROM (chip) that gives VE ( Volumetric Efficiency ) for a given RPM and MAP condition. 

It is more of a "formula" to achieve a 14.7 A/F ratio. 

The ECM tries to maintain 14.7 to 1. The reason is, 14.7 A/F ratio allows a catalytic converter to reduce exhaust emissions most efficiently. Engines don’t run the best at 14.7 all the time, but they produce the least emissions with a catalytic converter at this ratio. Also, the standard O2 sensor is most accurate at a 14.7 A/F ratio.

The O2 sensor does not actually measure oxygen concentration, but rather the difference between the amount of oxygen in the exhaust gas and the amount of oxygen in air. ... Lean mixture causes low voltage, since there is an oxygen excess.

In your O2 sensor picture the left bank is LEAN and should look more like the right O2 sensor, not Exactly, but closer to it.

I didn't want to write a thesis on long term and short term fuel trim or block learn and integrator values. Keep in mind that this type of fuel management control is 25 year old, old school technology. Now, there are pre-cat O2 and post-cat O2 sensors, ECM/PCM's processing much more information and adjusting fuel mixtures faster than you can imagine.

Edited by OldCadTech

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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It's okay to post a thesis here, professor!

Most us on this forum must certainly be amateurs like me, so only good can result from sharing the knowledge.

Maybe we could post some of this Block Learn info in a reference or 'sticky' part of the website.

I found some great website information that includes exactly what you said about Block Learn (BLM) and Integrator (INT) values:

http://carprogrammer.com/Z28/PCM/FAQ/How GM Electronic Fuel Injection Works.htm         (incomplete, but still helpful)

http://www.gnttype.org/techarea/faq/BLMINT.html         (about the Buick Regal, but still a very good and intuitive article)

 

I think maybe my earlier posting of the BLM and INT values doesn't help much because that is only just one 'Cell' situation where the Eldorado is idling at a fixed low RPM and low airflow.

The bottom line is that the rest of the 15 Cells (out of the total 16) are probably trying to correct a too-lean condition on the left bank of the engine, and not succeeding very well?

Please correct me if I'm saying anything incorrect.

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No need for the snide professor comments!

I'm not a professor, never claimed to be a professor. I simply understand the system as I attended a LOT of GM classes and diagnosed and worked with "it" when this was current model year technology. I stated I didn't want to do a thesis on BL and fuel integrator because the information is available all over the WWW as you have already found out for yourself. 

39 minutes ago, area310dude said:

The bottom line is that the rest of the 15 Cells (out of the total 16) are probably trying to correct a too-lean condition on the left bank of the engine, and not succeeding very well?

There are a total of 32 cells.

 

On 12/4/2017 at 7:56 PM, OldCadTech said:

The fuel integrator is what the ECM is commanding.

The block learn is that the left bank is trying to enrich the mixture and the right bank is is trying to lean the fuel mixture. It is running off a  pre-programmed "block" of parameter information to perform that task.

When you're ready to do the injector o-ring leak test it will tell you more than watching the integrator and BL values.

Edited by OldCadTech

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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No snide!

It was meant as a compliment, you taught me a lot here and I really, really appreciate it.

If I was in Washington State, there is a beer and a pizza slice (with your name on it) I would like to give you!

Personally I couldn't find that much on the WWW about BLM and INT, so whatever you have to say on the subject, I would absorb like a sponge.  Especially with your tremendous background of knowledge and experience.

sorry for the misunderstanding.

Edited by area310dude
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  • 3 years later...

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