2007 Grand Prix DIC errors but no OBD codes

**PrixMa** · 07-10-2020

My son has a 2007 Pontiac Grand Prix handed down to him by his older brother. 185k miles. No known problems other than an oil leak that we were going to deal with. DIC started showing errors - Reduced Power, something about brakes. OBD shows no errors. Took it in to mechanic who didn't get anything but a U1000 error on testing. He's thinking it's the main electronics going bad and is urging us to not put the money into it since electrical issues are hard to find. Car has aftermarket stereo that is not in well and in searching I'm finding that aftermarket stereos frequently cause issues with the wiring harness.

My questions:
* Is it worth replacing the aftermarket stereo with an OEM one (junyard?) to see if that fixes the issue?
* If we take out the aftermarket stereo would we be able to see issues with the wiring harness?
* Any other suggestions? Car runs great except for the damn DIC errors that are freaking my kid out. Shopped checked the car out prior to this and there were no obvious probs (except the oil leak)

**Hurricane87** · 08-02-2020

Originally Posted by PrixMa

My son has a 2007 Pontiac Grand Prix handed down to him by his older brother. 185k miles. No known problems other than an oil leak that we were going to deal with. DIC started showing errors - Reduced Power, something about brakes. OBD shows no errors. Took it in to mechanic who didn't get anything but a U1000 error on testing. He's thinking it's the main electronics going bad and is urging us to not put the money into it since electrical issues are hard to find. Car has aftermarket stereo that is not in well and in searching I'm finding that aftermarket stereos frequently cause issues with the wiring harness.

My questions:
* Is it worth replacing the aftermarket stereo with an OEM one (junyard?) to see if that fixes the issue?
* If we take out the aftermarket stereo would we be able to see issues with the wiring harness?
* Any other suggestions? Car runs great except for the damn DIC errors that are freaking my kid out. Shopped checked the car out prior to this and there were no obvious probs (except the oil leak)

Get the junkyard head unit, pull out the existing piece of crap, and jump up and down on it. Lots of times.

Someday people will learn that a) the sound comes out of the speakers, b) the technology in the head unit goes back to the 1970s at the newest and trivial oem suppliers like Pioneer have figured it out, and c) it is not worth not being able to drive at night for "better sound," especially sound that exists entirely in your head.

**Scottydoggs** · 08-02-2020

id just take power away from the radio, that will disable it. see if the code goes away.

if it dont it could be the pcm is crapping out. you can get replacements from a junk yard or ebay for like 40 bucks of same year and model as your car, but if you have inspection it will fail because the vin wont match. on ebay theres sellers who can set the vin for your year and model for like 150 ish.

**Turbocharged400sbc** · 08-02-2020

std scanners wont give you much, my snapon 2500 "red brick" scanner sometimes doesnt capture em.

04+ 3800 drive by wire systems dont have true OBD (on board diagnostic) functions like the rest of the powertrain, the DBW computer is p[art of the tb and the PCM "ASSuMEs" that its always good, even though the TB or the pedal position sensor (the pedal assembly) are bad, it will only trigger reduced power but not an actual; code.

at that mileage id start with the pedal position sensor, its a plug and two 10mm hex bolts at the right foots toes, and i got 2 of em from the junkyard for 10$ each, new arent that much, tb's do fail but id start with the sensor, so many times ive seen others start with the tb and end up replacing the cheap[er pedal sensor afterwards to fix it

**PrixMa** · 08-03-2020

So... checked stereo wiring harness and no obvious issues but at least we were able to check that connections were all good and that they used a "good" wiring harness. (Haven't ruled out ripping the damn thing out and stomping on it.) Unfortunately, that wasn't our magic cure - got TPS warning on the DIC, reduced power and P2138 (Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation) and P1125 (Accelerator Pedal Position Sensor Fault) on OBD-II. Had tires checked/rotated - TPS started working again, but they they said battery was failing in it (which of course means replacing the TPS). Based on the codes and neurotic research, replaced the accelerator pedal sensor and cleaned the throttle body. (Picture is AFTER we rubbed at it enough to get that lighter spot in the carbon buildup. Definitely needed the cleaning.) He's driven it several more times and no reduced power, no error codes other than TPS warning (replacing it tomorrow). So far it's looking and running good, including not needing to give it gas when he starts it!! I'm going to be pretty damn proud if this fixes it since mechanic was ready to write it off!! Thought we had a leak in the windshield washer fluid reservoir since it was running down behind the tire after using the wipers... reservoir and hoses are good but when you use the wipers it's spraying a TON, enough to puddle up on the cowl grill and run... ran out of time to look at the nozzles to see if they're plugged and causing it. Guess that's what next Saturday is for.

Thanks for the help and suggestions! Greatly appreciated.