2008 Buick Lucerne CX :Service Traction control and engine power reduced

I bought this Gorgeous Buick as a project. It has been hit in the driver’s door. It has several OBD II codes.

P1516 Throttle actuator control module throttle actuator position performance.

P1125 Accelerator Pedal position sensor fault

P2138 Accelerator pedal position sensor 1-2 correlation

U0107 Lost communication with throttle actuator control module.

It also has a display on the dash that says “SERVICE TRACTION CONTROL” and “ENGINE POWER REDUCED”.

It does not run with peak performance. No kidding…

The former owner says the traction control issue happened with the accident. She’s not sure about the codes. Obviously the brakes were used hard at that moment, but isn’t that what they are for? The car may or may not have been pushed sideways. The damage is not that deep. I don’t see a code that relates to the traction control with my cheap Mac Tools scanner.

Are these two issues related?

What should I look for first?

I agree, this is definitely a project!!

My guess, the traction control and the throttle actuator problems are not related. The traction control is probably a skipping wheel speed sensor, which should be easy to diagnose, but if you want to do it yourself you’ll probably need a more fancy scan tool than the one you have. The throttle actuator, all that may be necessary is a good cleaning of that and possibly the throttle body. I’d start with that.

This is a drive-by-wire throttle body on this vehicle.

Get on the web and look up everything you can learn about this system.

When the drive-by-wire throttle doesn’t work, it knocks out other systems that are related to the throttle.

Have fun!


If you have a powertrain performance issue with this vehicle, which there obviously is, ignore the traction control message for now and focus on the throttle codes. The traction control system relies on a normally performing powertrain. If powertrain is not functioning properly, the traction control will be disabled and the light will be on. I would start by looking for bad/severed wires from collision.

Now here’s a weird situation. Because I hate automotive electrical problems, I took the Lucerne to a trusted shop that specializes in electrical systems and situations this morning. I’ve used them several times, but they are under new ownership since I first discovered them 20 years ago. They called a couple of hours later to say that it needed a throttle pedal with its attached sensor and the fly-by-wire throttle body. Supposedly aftermarket parts are not available. It’s GM only. Their estimate was $970.34. I can buy used parts for $125. I happily paid their $80 diagnostic fee. Now here’s the weird part. The car runs perfectly. I drove it 12 miles back here, some interstate, some city streets. No problem. The MIL was still on, but I erased it after I got back. It has not come back. So what happened? Did they unplug one or both of the multi-pin connectors and accidentally clean something up? Did they know they’d fixed it? Any chance it’ll stay fixed? I think I’ll drive it a few days and see what happens.

Aftermarket accelerator pedal/sensors ARE available for this car at RockAuto. The funny thing is they’re listed under the category “Interior”. They’re only about $65. Don’t know how good they are.

@MY_2_CENTS At least I know they lied about that part of the situation. That doesn’t give me a warm fuzzy feeling.

Cross your fingers

It’s possible that by unplugging the throttle body and pedal position sensor, they were “reset” . . . hopefully the fix is permanent

I’m skeptical of the diagnosis, because they want to sell you the throttle body AND the pedal position sensor . . . sounds to me like they’re not too sure, themselves

On the other hand, GM has several TSBs, concerning throttle bodies, and the fix is to either replace them with an updated part, or replace a part of the throttle body

Rockauto shows an AC Delco complete throttle body, for well under 200 bucks, for the 3.8 engine . . . and if you’ve got the 4.6, it’s well under 100 bucks