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03 CTS Rough Idle & Hard Shift


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Hey everyone, I have been fighting this problem for more than several months now and everytime I think I have it fixed it comes right back and bites me just before I begin to get comfortable. Some people ask me "why not trade it in" IDK maybe im stubborn but I like my car else I would'nt have bought it I would like to deck her out a bit aswell but before I do that she needs to run right.

If anyone is willing to take a moment of their time and help me with any experience they have with this issue it is highly appreciated. At first glance the probable causes of this problem is not the actual problem it is so computerized that something from left field affects something in right field so to speak. It is not a slipping transmission the tranny was already replaced for that conception, what a darn waste.

Anyways, the vehicle exerts many codes, however these codes play possum alot so it would lead me to think they are misconceptions from the on board computer itsself so I will try and work with solid experieces, and yes the PCM was replaced so its not a bad PCM.

The car will randomly exert hard shifts the shifts feel somewhat like doing a neutral drop on a car, that is when the car is in neutral and you increase the RPMs untill you shift it into Drive or 1st gear. This happens while up shifting or down shifting. During this the engine light is ussually on and showing yellow. Randomly wether I am idleing or wether I am doing 70 on the freeway the "Engine power Reduced" message will flash on the vehicles display and all but enough power to idle is cut to the engine. I have to pull over shut the car off and restart in order to be able to even move again. Randomly also will get "Service Idle control" Message. I have no clue where on the car the Idle control is, and I am here seeking help from the caddy community so I can avoid the garage at all costs, I can't afford it bottom line and they want to replace a ton of stuff which is not the problem like my transmission and from other posts on this topic all over the internet, I wont be the first if I said OK and never got the problem resolved.

Has anyone succesfully repaired this issue on a 2003 CTS?

Things I have done that seem to take affect on the issue but never fully resolve the issue.

1. I have "gotten" a transmission replaced,

2. and I have "gotten" the PCM replaced "No Go".

3. Relearn Idle procedure from garages and Cadillac themselves, still the problem will go away for 2 weeks - 1 month and then come back.

4. I have reset the computer by unplugging the terminals to the battery this has a random effect on how long it fixes the problem sometimes for 30 seconds sometimes for a week.

5. I have replaced the mass air flow sensor it seemed to work for a day giving me the car with the driveability I always wanted, a day later it was back with a vegance.

6. Sometimes shifting from park to Drive then back to park and back to drive remedys the problem extremely temporarily.

7. I have reseated the Mass air flow sensor wire harness dozens of times I get random effects from it, sometiems remedy's the problem for the day sometiems 2 minutes sometimes a few hours, it's very random.

8. Last week I changed my air filter, cleaned my throttle body out with carb cleaner as best as I could and it already looked pretty clean. So far the Check engine light is out and it has gone out before plenty of times, but I know it will come back eventually with same issues.

So where the hell do go to finally put a nail in this problem's coffin?

What have people done to fix this?

Above is one problem.

Last week after plugging everything in I lost all power control from the driver's side door panel No windows, no locks, no trunk release. However when put into drive all doors still lock and when put into park the still all unlock, so I know they are getting power 1 way or another I simply just dont understand where to find the fuse for this and looking at all my fuses they all look good I just need to OHM them out to a sure test.

Where can I start to troubleshoot this other problem now? Any assistance for both issues is greatly appreciated.

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Now that you have aired your frustrations, the first thing you need to do is to post any codes you have been getting, they are NOT random anomolies, they will direct us to the problem

You seem overwhelmed with the computers with this statement "At first glance the probable causes of this problem is not the actual problem it is so computerized that something from left field affects something in right field so to speak ".

Lets not try to make assumptions.

Why was the transmission replaced?

Who is your mechanic?, this is important, has it been to a cadillac dealer or local mechanic... details

Post your codes... there are MANY codes that can cause your problems. Bruce who runs this site had a problem with his CTS where a module needed replacing.

We need codes first.... VERY VERY IMPORTANT

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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  • 5 months later...

Hey guys, I think I've finally figured this problem out!

I also got the reving idle and then intermittent red-line revs, rough shifting, engine codes, reduced power, and on and on....

I replaced the ECU, the MAP, and wiring harness...none of which fixed the issue. So after spending over 1k on parts and labor, in frustration I removed the throttle assembly and took it apart.

The problem was inside the black plastic side cover. When you remove the six stainless steel clips from the plastic cover, you can then split it apart. Once inside there are 4 tiny contact that touch on a pad which is on the plastic side. Mine looked clean but I used an electrical contact spay cleaner on both the contacts and the pad and wiped with a clean towel.

After that I put everything back together and started the car.....It now runs perfect!!!

I still need to do the idle relearn procedure just for the heck of it, but the car now runs better than ever, shifts fine and all of the issues have gone away.

I hope this helps anyone with the same issues...I know how frustrating it can be!

Best of luck!

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  • 4 weeks later...

Hey everyone, I have been fighting this problem for more than several months now and everytime I think I have it fixed it comes right back and bites me just before I begin to get comfortable. Some people ask me "why not trade it in" IDK maybe im stubborn but I like my car else I would'nt have bought it I would like to deck her out a bit aswell but before I do that she needs to run right.

If anyone is willing to take a moment of their time and help me with any experience they have with this issue it is highly appreciated. At first glance the probable causes of this problem is not the actual problem it is so computerized that something from left field affects something in right field so to speak. It is not a slipping transmission the tranny was already replaced for that conception, what a darn waste.

Anyways, the vehicle exerts many codes, however these codes play possum alot so it would lead me to think they are misconceptions from the on board computer itsself so I will try and work with solid experieces, and yes the PCM was replaced so its not a bad PCM.

The car will randomly exert hard shifts the shifts feel somewhat like doing a neutral drop on a car, that is when the car is in neutral and you increase the RPMs untill you shift it into Drive or 1st gear. This happens while up shifting or down shifting. During this the engine light is ussually on and showing yellow. Randomly wether I am idleing or wether I am doing 70 on the freeway the "Engine power Reduced" message will flash on the vehicles display and all but enough power to idle is cut to the engine. I have to pull over shut the car off and restart in order to be able to even move again. Randomly also will get "Service Idle control" Message. I have no clue where on the car the Idle control is, and I am here seeking help from the caddy community so I can avoid the garage at all costs, I can't afford it bottom line and they want to replace a ton of stuff which is not the problem like my transmission and from other posts on this topic all over the internet, I wont be the first if I said OK and never got the problem resolved.

Has anyone succesfully repaired this issue on a 2003 CTS?

Things I have done that seem to take affect on the issue but never fully resolve the issue.

1. I have "gotten" a transmission replaced,

2. and I have "gotten" the PCM replaced "No Go".

3. Relearn Idle procedure from garages and Cadillac themselves, still the problem will go away for 2 weeks - 1 month and then come back.

4. I have reset the computer by unplugging the terminals to the battery this has a random effect on how long it fixes the problem sometimes for 30 seconds sometimes for a week.

5. I have replaced the mass air flow sensor it seemed to work for a day giving me the car with the driveability I always wanted, a day later it was back with a vegance.

6. Sometimes shifting from park to Drive then back to park and back to drive remedys the problem extremely temporarily.

7. I have reseated the Mass air flow sensor wire harness dozens of times I get random effects from it, sometiems remedy's the problem for the day sometiems 2 minutes sometimes a few hours, it's very random.

8. Last week I changed my air filter, cleaned my throttle body out with carb cleaner as best as I could and it already looked pretty clean. So far the Check engine light is out and it has gone out before plenty of times, but I know it will come back eventually with same issues.

So where the hell do go to finally put a nail in this problem's coffin?

What have people done to fix this?

Above is one problem.

Last week after plugging everything in I lost all power control from the driver's side door panel No windows, no locks, no trunk release. However when put into drive all doors still lock and when put into park the still all unlock, so I know they are getting power 1 way or another I simply just dont understand where to find the fuse for this and looking at all my fuses they all look good I just need to OHM them out to a sure test.

Where can I start to troubleshoot this other problem now? Any assistance for both issues is greatly appreciated.

@ blackcaddy10, I have the exact same problem, ive heard something about changing the wiring harness for the throttle body, have you fixed this for good? any info would greatly help me bro. Thanks.

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  • 5 months later...

Hey everyone, I have been fighting this problem for more than several months now and everytime I think I have it fixed it comes right back and bites me just before I begin to get comfortable. Some people ask me "why not trade it in" IDK maybe im stubborn but I like my car else I would'nt have bought it I would like to deck her out a bit aswell but before I do that she needs to run right.

If anyone is willing to take a moment of their time and help me with any experience they have with this issue it is highly appreciated. At first glance the probable causes of this problem is not the actual problem it is so computerized that something from left field affects something in right field so to speak. It is not a slipping transmission the tranny was already replaced for that conception, what a darn waste.

Anyways, the vehicle exerts many codes, however these codes play possum alot so it would lead me to think they are misconceptions from the on board computer itsself so I will try and work with solid experieces, and yes the PCM was replaced so its not a bad PCM.

The car will randomly exert hard shifts the shifts feel somewhat like doing a neutral drop on a car, that is when the car is in neutral and you increase the RPMs untill you shift it into Drive or 1st gear. This happens while up shifting or down shifting. During this the engine light is ussually on and showing yellow. Randomly wether I am idleing or wether I am doing 70 on the freeway the "Engine power Reduced" message will flash on the vehicles display and all but enough power to idle is cut to the engine. I have to pull over shut the car off and restart in order to be able to even move again. Randomly also will get "Service Idle control" Message. I have no clue where on the car the Idle control is, and I am here seeking help from the caddy community so I can avoid the garage at all costs, I can't afford it bottom line and they want to replace a ton of stuff which is not the problem like my transmission and from other posts on this topic all over the internet, I wont be the first if I said OK and never got the problem resolved.

Has anyone succesfully repaired this issue on a 2003 CTS?

Things I have done that seem to take affect on the issue but never fully resolve the issue.

1. I have "gotten" a transmission replaced,

2. and I have "gotten" the PCM replaced "No Go".

3. Relearn Idle procedure from garages and Cadillac themselves, still the problem will go away for 2 weeks - 1 month and then come back.

4. I have reset the computer by unplugging the terminals to the battery this has a random effect on how long it fixes the problem sometimes for 30 seconds sometimes for a week.

5. I have replaced the mass air flow sensor it seemed to work for a day giving me the car with the driveability I always wanted, a day later it was back with a vegance.

6. Sometimes shifting from park to Drive then back to park and back to drive remedys the problem extremely temporarily.

7. I have reseated the Mass air flow sensor wire harness dozens of times I get random effects from it, sometiems remedy's the problem for the day sometiems 2 minutes sometimes a few hours, it's very random.

8. Last week I changed my air filter, cleaned my throttle body out with carb cleaner as best as I could and it already looked pretty clean. So far the Check engine light is out and it has gone out before plenty of times, but I know it will come back eventually with same issues.

So where the hell do go to finally put a nail in this problem's coffin?

What have people done to fix this?

Above is one problem.

Last week after plugging everything in I lost all power control from the driver's side door panel No windows, no locks, no trunk release. However when put into drive all doors still lock and when put into park the still all unlock, so I know they are getting power 1 way or another I simply just dont understand where to find the fuse for this and looking at all my fuses they all look good I just need to OHM them out to a sure test.

Where can I start to troubleshoot this other problem now? Any assistance for both issues is greatly appreciated.

@ blackcaddy10, I have the exact same problem, ive heard something about changing the wiring harness for the throttle body, have you fixed this for good? any info would greatly help me bro. Thanks.

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  • 2 years later...

Hi guys I don't know much about this but I've been having the same problem with my 03 Cadillac cts.i want to know what's step one to solve this problem.I've changed my transmission 3 time And throttle body meany times also my computercar.won't re-learn and shifts hard and looses power often. My mechanic said i need to change my loom now?asking or HELP!!! I love my car just want to get it right but now it's really hurting me moneywise :/

thanks.

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I don't see any codes listed. As far as hard shifting, check the Transmission Control Module. It may need to be replaced or reprogrammed. This is something a Cadillac dealership should check. I understand that you can reset everything by disconnecting battery cables and holding them together for about 5-10 seconds. But I have not done this, so I suggest doing some research about it. My research indicates this is correct.

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The original three-year-old complaint was fixed by cleaning scratch contacts on the gas pedal throttle-by-wire. Maybe that should be looked at first along with the cables and such. I would check the OBD codes against the driveability complaints before I went to the trouble and expense of replacing a module.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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