2001 Pontiac Grand Am "Trac Off"/ETS Malfunction


#1

2001 Pontiac Grand Am SE 4-door sedan, automatic transmission, 2.4L 4-cylinder inline, front-wheel drive, 146000 miles.

The issue:

  • “Trac Off” light will come on seemingly at random. No other light will come on; the “Service Engine Soon” and “ABS” lights stay off. Cruise control does not work while the light is on. Also it can no longer accelerate to top speeds; I can floor the gas pedal and it will just sit at ~2200 RPM and 72 MPH. It also seems to shift more violently and idle less steadily. Turning the car off and restarting resets the light, and everything including cruise control works normally again.
  • Had a store scan the codes right after it happened one time and it read:
    –C1275 “Powertrain Control System Requested ETS To Be Disabled”
    –P0122 “Throttle / Pedal Position Sensor A Circuit Low Input”
    –P0302 “Cylinder 2 Misfire Detected”
    –Scanning the computer after it didn’t happen read the P0122 and P0302 codes but not the C1275 code.
  • It has happened most often on the highway while using cruise control, but has also happened on city streets and while not using cruise control.
  • Nothing consistent seems to cause it and infrequent. When it does happen it tends to happen again within the same trip/day. Usually it takes at least 15-20min driving before it happens for the first time within a trip. I took the car to a mechanic one day and they couldn’t troubleshoot it because the malfunction wouldn’t even happen for them from only driving on city streets.
  • For example, I drove from Chicago to Milwaukee and it happened a couple of times. Two days later I drove back to Chicago and manually turned the ETS off (ETS button the dash) and had no trouble. Then I drove Chicago to NYC and it did not happen until going up the hills in Pennsylvania.

Car otherwise runs well for its age and there are no issues while driving except when this occurs. I first noticed it occuring in the middle of last winter (I did not drive it most of the summer due to travel). I’m worried that this could indicate a larger problem. Could it be a sensor issue? A wiring issue? Or something wrong with the transmission?

I am also concerned that this could be safety issue in the winter if a ETS malfunction would affect the anti-lock braking system. I want to sell the car but do not know what to tell potential buyers. It seems like a problem that will remain unknown until something actually breaks.

Any suggestions would be much apprecaited!


#2
Two days later I drove back to Chicago and manually turned the ETS off (ETS button the dash) and had no trouble. Then I drove Chicago to NYC and it did not happen until going up the hills in Pennsylvania.

If the ETS was ON going to NYC, I would turn it off every trip until convinced either that solves the problem or not, then go from there.


#3

The p codes are the likely culprit causing the trac off request. If the powertrain can not be controlled as planned, it will turn off trac control since it can no longer calculate torque properly.


#4

Insightful: I agree with your input; the ETS indeed was ON going to NYC. However, I believe the ABS needs the ETS to be on to function properly. With winter coming up that would be a safety issue.

Pete: That makes sense. Do you think it is a sensor issue?


#5

@Gedy4 , I don’t think you’re correct that an ETS issue will cause ABS not to function. If that were so, the ABS light would be on as well. And, turning off the ETS manually would also disable the ABS, which wouldn’t make sense design-wise.

I’ve driven a car that had a manual switch for disabling the stability control system and I’m pretty sure that doing so did not affect the ABS.


#6

@jesmed1 I was thinking that because the ABS relies on input from the same wheel speed sensors that the ETS uses. But you are right that the ABS light would be on as well if it were a problem affecting both. And that this does not mean the ABS needs the ETS to be on to function problem. This seems to show that the wheel speed sensors are not malfunctioning; I need to figure out what is causing the powertrain control system to request ETS to be disabled.

Quickly looking up the C1275 error with Grand Ams with this engine and I’ve read that it could be due to a faulty intake air temp sensor. I would expect this to cause other errors. The Service Engine Soon light has come on, although not every time.


#7

I should note that the faulty IAT also seems unlikely because there have been no error codes for low or high temperature readings (P0112 or P0113), gas mileage is fine, and there hasn’t been any black smoke coming out of the tailpipe.