Check Engine and reduced power
Thread Starter
Instructor
Joined: Jul 2004
Posts: 108
Likes: 0
From: North Wales PA
Check Engine and reduced power
I have a 97 C5 A6 71,000 miles. Runs smooth. Today after hitting a bump in the road, the ABS malfunction and anti lock malfunction words come up on the display. In addition, the Engine reduces power including wording to that effect on the dashboard, followed by the check engine light remaining on. I hit reset to clear the error messages and pulled over "under reduced power" and shut her dowm. I quickly restarted the car with no problems and with full power. The Check Engine light remained on however. The only thing that makes sense to me is that the reduced power has a coorelatio to the anti lock / abs error message. Without ABS and anti lock, the computer sends a signal to reduce engine power. Any other experience with this??
BTW, the abs/antilock error has popped up almost every day for 2 weeks after hitting a bump in the road, and clearing the error message and restarting the car clears the antilock symbols.
BTW, the abs/antilock error has popped up almost every day for 2 weeks after hitting a bump in the road, and clearing the error message and restarting the car clears the antilock symbols.
Team Owner
Joined: May 2002
Posts: 24,459
Likes: 13
From: Phoenix
St. Jude Donor '03-'04-'05-'09
You may want to get it on a rack and get the brake hardware checked...as for the reduced power message, welcome to the club 
This seems to be a somewhat common proble (occasionally) usually shutting off your motor, (re-boot) then re-stating will clear this. Some have found getting there code history scanned, common errors that may or may not relate to this...or anything 
Mine did this...showed a TB sensor positioning switch error. I decided to replace the switch...never did it since. Welcome to technology
This seems to be a somewhat common proble (occasionally) usually shutting off your motor, (re-boot) then re-stating will clear this. Some have found getting there code history scanned, common errors that may or may not relate to this...or anything Mine did this...showed a TB sensor positioning switch error. I decided to replace the switch...never did it since. Welcome to technology
Thread Starter
Instructor
Joined: Jul 2004
Posts: 108
Likes: 0
From: North Wales PA
Thanks Scratch! Your reply is clear -- I'll get it up in the air to eyeball the brakes etc and also get it scanned for error codes. You are right that the restart did seem to clear up the reduced power issue, I was more afraid that I'd reduce power on the highway.
Thanks again!!
Thanks again!!
Pro
Joined: Feb 2001
Posts: 539
Likes: 6
From: Far NW burbs of Chicago IL
Might also be the knock sensor. Not 100% sure if they are on our motors, but I had this happen before on another car.....the sensor throws a code and retards the timing to significantly reduce the power.
Thread Starter
Instructor
Joined: Jul 2004
Posts: 108
Likes: 0
From: North Wales PA
I will share my findings after lifting the car tomorrow morning. The next trick will be either figuring out how to get the codes without "the tool" and then resetting the "check engine" light.
USMC (retired)
Joined: Aug 2004
Posts: 3,267
Likes: 4
From: Wimauma FL
Hope you clear the problem up. This sounds similar to what is happening to my C4...the check engine would come on and you can feel the reduced power.
My C5 has not shown any problems though.
My C5 has not shown any problems though.
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Thread Starter
Instructor
Joined: Jul 2004
Posts: 108
Likes: 0
From: North Wales PA
Keeping those interested up to date... I checked the codes and returned with a bunch of them
P1518 H - TAC Module serial data circuit
P1571 H - ASR desired toque
P1626 H - Theft deterrent system fuel enable circuit
C1225 H - RF Excessive wheel speed variation
C1255 H - EBTCM Internal Malfunction
C1278 H - TCS temporarily inhibited by PCM
After clearing and the running the care for a few seconds, the only code that returned was P1571 H
Starting to feel more like a problem that is linked to the ABS. Later today, I'll check under the car for wheel speed sensor connection problems or potential intermittent grounds. Based on C1225 H, I'll start with the RF wheel. I fire back with findings later today.
P1518 H - TAC Module serial data circuit
P1571 H - ASR desired toque
P1626 H - Theft deterrent system fuel enable circuit
C1225 H - RF Excessive wheel speed variation
C1255 H - EBTCM Internal Malfunction
C1278 H - TCS temporarily inhibited by PCM
After clearing and the running the care for a few seconds, the only code that returned was P1571 H
Starting to feel more like a problem that is linked to the ABS. Later today, I'll check under the car for wheel speed sensor connection problems or potential intermittent grounds. Based on C1225 H, I'll start with the RF wheel. I fire back with findings later today.
Advanced
Joined: Jun 2004
Posts: 71
Likes: 0
From: Upstate NY NY
I had a similar situation which I found to be a loose wire connection in the passenger door. I would get the same messages and then the passenger door power window and locks would stop working. If I opened the door and slammed it or wiggled the rubber boot covering the wires in the hinge area it would go away. I haven't taken the door off to find the exact problem as it hasen't done it in awhile. Try your passenger power controls next time it happens and see if it's a similar problem.
Good Luck!
Good Luck!
Pro
Joined: Jan 2004
Posts: 504
Likes: 0
From: Monroe LA
This maybe off base but I have gotten the "Reduced Engine power" and all the abs stuff from the MAF being unpluged. I guess the bump could have loosen the connection?
Good luck on tracing your problem down!
Good luck on tracing your problem down!
Le Mans Master
Joined: Jun 2000
Posts: 6,899
Likes: 6
From: Long Valley NJ
St. Jude Donor '03-'05-'06-'07-'08,'11 thru '17, '21
A while ago, I had the "excessive wheel speed variation" code, which caused "service ABS" or "service TCS" messages to appear. I my case, I fixed it by removing & reinstalling the short wiring harness that goes from the frame out to the wheel speed sensor. I took it off to test for intermittent connections, since I heard that the harness section is a common failure point. I found nothing wrong with it, reinstalled it, and have never had the problem again. I think it may have been a dirty or loose connector.
So you may want to try pulling & reseating the connectors on each end of that harness.
So you may want to try pulling & reseating the connectors on each end of that harness.
