Running Rough, Reduced Power, DTC's, HELP!
Thread Starter
Pro
Joined: Dec 2000
Posts: 690
Likes: 202
From: Hoffman Estates, IL
Running Rough, Reduced Power, DTC's, HELP!
Started the '97 C5 up and it idled poorly. Check engine light came on solid and IPC read "REDUCED ENGINE POWER" and the stupid door chime starts beeping rapidly. I idled it for a minute to see if it would go away and it didn't so I shut it down. Cleared all codes, waited 30 min, restarted it, and same thing happened. IPC spit out the following:
10 PCM:
P1516 - Command vs Actual Throttle Position Performance (TAC Module) -A
P1571 - ASR Desired Torque -C
28 TCS
C1278 - TCS Temporarily Inhibited by PCM
All this just came out of the blue. Please tell me what I need to do to fix the problem. I'm new to the C5 so help is appreciated. My educated guess and limited knowledge of the above DTC's tell me something like this...
by looking under the hood it looks like the C5 does not have a throttle cable, but rather a motor which controls throttle position, sort of a drive by wire system for the throttle body plate. Maybe if the TPS is not reading the same %throttle as the PCM is commanding the throttle motor to be at, then the above code would be set?!? Do I need a new throttle motor?
As for the ASR desired torque code, I have no idea on that one. I assume the last code "TCS temp disabled by PCM" is a result of the P1571 code.
:sad:
10 PCM:
P1516 - Command vs Actual Throttle Position Performance (TAC Module) -A
P1571 - ASR Desired Torque -C
28 TCS
C1278 - TCS Temporarily Inhibited by PCM
All this just came out of the blue. Please tell me what I need to do to fix the problem. I'm new to the C5 so help is appreciated. My educated guess and limited knowledge of the above DTC's tell me something like this...
by looking under the hood it looks like the C5 does not have a throttle cable, but rather a motor which controls throttle position, sort of a drive by wire system for the throttle body plate. Maybe if the TPS is not reading the same %throttle as the PCM is commanding the throttle motor to be at, then the above code would be set?!? Do I need a new throttle motor?
As for the ASR desired torque code, I have no idea on that one. I assume the last code "TCS temp disabled by PCM" is a result of the P1571 code.
:sad:
Melting Slicks
Joined: Oct 2001
Posts: 2,075
Likes: 0
From: Central NJ
Re: Running Rough, Reduced Power, DTC's, HELP! (Godspeed)
Have you tried clearing the codes and see if they come back?
If that doesn't work, check the underhood fuse for the throttle actuator module. If it's blown, check your wiring harness where it goes around the injector rail on the driver's side for a short to ground :cheers:
Melting Slicks
Joined: Feb 2002
Posts: 2,613
Likes: 0
From: Winston Salem NC
Re: Running Rough, Reduced Power, DTC's, HELP! (JCOB2)
You might post in the "Induction/Nitrous" section. I remember reading a while back about SC cars needing to program a defeat for an air flow test. Did you reprogram prior to the problem?
Melting Slicks
Joined: Feb 2001
Posts: 3,360
Likes: 1
From: DFW TX
Senior Member
Cruise-In III Veteran
Cruise-In IV Veteran
Re: Running Rough, Reduced Power, DTC's, HELP! (jfpilla)
You might post in the "Induction/Nitrous" section. I remember reading a while back about SC cars needing to program a defeat for an air flow test. Did you reprogram prior to the problem?
Thread Starter
Pro
Joined: Dec 2000
Posts: 690
Likes: 202
From: Hoffman Estates, IL
Re: Running Rough, Reduced Power, DTC's, HELP! (Godspeed)
Godspeed - do you mean the 1516 code? The 1514 code I can see, greater airflow than expected through MAF... but I don't see how a blower would cause a discrepency in the TPS vs. TAC percentages.
Anyways... I popped the hood, pulled the TAC fuse and it was fine. Looked at the wires/connector and they looked fine too. On my Camaro, there used to be a trick to reset the TPS sensor, so I tried it on the Vette incase Chevy engineered it the same. To reset the TPS voltage reading and IAC valve position I put the iginition in the "accessory on" position, floor the accelerator and hold it for 10 seconds, then release and turn off the ignition. Cleared the codes, restarted the car, and it was fine. Turned it off, restarted again, and it was still fine. So, who knows... stupid Chevy and their intermittent codes!!! :cuss Hopefully this won't turn into a chronic issue... :nopity
Anyways... I popped the hood, pulled the TAC fuse and it was fine. Looked at the wires/connector and they looked fine too. On my Camaro, there used to be a trick to reset the TPS sensor, so I tried it on the Vette incase Chevy engineered it the same. To reset the TPS voltage reading and IAC valve position I put the iginition in the "accessory on" position, floor the accelerator and hold it for 10 seconds, then release and turn off the ignition. Cleared the codes, restarted the car, and it was fine. Turned it off, restarted again, and it was still fine. So, who knows... stupid Chevy and their intermittent codes!!! :cuss Hopefully this won't turn into a chronic issue... :nopity
Racer
Joined: Apr 2001
Posts: 314
Likes: 0
From: Plano Texas
Re: Running Rough, Reduced Power, DTC's, HELP! (JCOB2)
The exact same thing happened to me this past Sat. morning. I had been out in the car earlier that morning so it was still warm and everything. Anyhow, when I first started it did the exact same thing. So after about 10 seconds I shut it off and then restarted it. Again, the same thing happened. This time after i turned it off I pulled the key out and opened my door to make the seat move all the way back as if I was exiting the car. After abopiut a minute, I closed the door and restarted the car and everythig was fine except for the check engine light being on. That too disappeared later that day after simply driving it normaly throughout the day. This has happened to me twice before with the same end results. Now the car runs just fine!
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Melting Slicks
Joined: Feb 2002
Posts: 2,613
Likes: 0
From: Winston Salem NC
Re: Running Rough, Reduced Power, DTC's, HELP! (JCOB2)
Do you have Edit? If it happens again, it can't hurt to toggle off the 1516 test.
The other codes are likely nothing. Just guessing, but it seems like a worthwhile thing to try.
The other codes are likely nothing. Just guessing, but it seems like a worthwhile thing to try.
