I have an '08 Vert with AT and the NPP option. Seven times since purchasing the vehicle in 01/09 the dash goes "ding-ding-ding" and a 3 part message flashes across the DIC:

>Reduced Power
>Service Traction Assist
>Comp Driver Mode

and the check emission light comes on. You have virtually no pedal and have to limp home all the while the trans is jerky on downshifts.

The local dealer has serviced the unit 3 times with the last service having them replace the gas pedal position sensor and hardwire everything back to ??? something and things have been fine for 5K miles. Now the problem is back.

Ideas - suggestions? I find I don't trust the vehicle to go on trips. DC'ing the battery corrected the problem only to have it return.

Thanks for your help!

 

Hmmmm......the first things I would check are the simple things:

1. The AH/TC button switch on the console
   
2. The wheel speed sensors

With the "Service Traction System" message you got, the dealer should have a good idea of what to check.

You say they "serviced the unit 3 times", but what "unit" did they service??? Was it the EBCM??? The RIM???

The Service Manual says that the TCS (Traction Control System) works through the IPC (Instrument Panel Cluster) sending serial data messages to the EBCM (Electronic Brake Control Module), which is the brain of the ABS. There's a thing called the RIM (Rear Integration Module) that detects if you push the console button to turn off TC.

If the TCS detects the rear wheels spinning, it will retard timing and turn off fuel injectors - and that will give the "Reduced Power" message you see. It detects wheel spin through the wheel speed sensors.

If the power reduction doesn't work, it will put on rear brakes.

So.....

First thing I'd check is the button/switch on the console.

I'm sure they must have checked the sensors that detect loss of traction/wheelspin that send the message to TCS to go into action. That's what I would check second!!!

Third, I'd check the RIM.

That message about "Comp Driver Mode" makes no sense. The only time you should see the message "Competitive Driving Mode" is when you make the selection yourself with the button on the console.

The Comp Driving Mode should NEVER be invoked without you pushing the TC/AH button to deliberately select it!!!

That's why I'm very suspicious of your console button/switch. And considering the RIM is what tells the system if you've pushed that button, I'd check it as well.

What happens when you push the AH/TC button?

There are 4 modes that you can put the AH/TC into with the button:

1. When you start up the car, it defaults to - AH ON: TC ON
   
2. When you push the button once - TC is turned OFF
   
3. A second push within 5 seconds - TC is OFF; AH goes into Comp Mode
   
4. Push and hold the button for more than 5 seconds (hold it down until the message displays in the DIC) - TC is OFF; AH completely OFF

Are you able to get the systems to go into the modes above with the corresponding messages in the DIC?

BTW, I assume you have stock wheels and tires. If you have some aftermarket wheels/tires that are quite different in size from the OE front/rear ratio, you might cause problems that the ABS/EBCM would think is spinning tires. Usually this is due to a larger rear tire that gives an "Engine Drag Control Active" message, but I guess if the ratio is off the other way the system might think the rear wheels are spinning too fast and interpret that as a TC issue.

Good luck!

Bob

 

Bob

WOW! Excellent reply!


Bill

 

The car is a system of systems and those systems are interwoven together to provide certain high level functions.

I don't think your problem is being caused by the traction control or active handling systems. The Reduced Power Message is telling you there is a problem with the throttle control system. The other messages get triggered if there is a problem with the throttle control system and a DTC code is generated. That is why the dealer replaced all of those items mentioned in your post. The EBCM can also raise a Service Traction Control message if the BCM sends it a message upon the BCM detecting a throttle control problem. There are two EBCM diagnostic codes that can show up:
C0242 and C0561 when a throttle control problem is reported. Both of these generate the Service Traction Control message.

You can go back to the dealer since you should still be under warranty or the repair itself will have a 12/12 warranty on it.

Here is an explanation of what is happening when you see Reduced Power.

Reduced Engine Power Mode
When the ECM detects a condition with the TAC system, the ECM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
• Acceleration limiting--The ECM will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.

• Limited throttle mode--The ECM will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.

• Throttle default mode--The ECM will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.

• Forced idle mode--The ECM will perform the following actions:
- Limit engine speed to idle by positioning the throttle position, or by controlling the fuel and spark if the throttle is turned off.
- Ignore the accelerator pedal input.

• Engine shutdown mode--The ECM will disable fuel and de-energize the throttle actuator.


Bill

 

Have you dealer check the harness conector at the transmission. The conector pulls the pin out just enough that you end up with a intermitent conecton problem. the black with red wire is a problem wire. this will cause the harsh shifts and reduced engine problem along with traction control and ABS . If you pull the codes out of the car you'll find U codes with loss of commucation to just about every module in the car.