(Help) how to get my car out of reduced power mode


Asked by Apr 02, 2014 at 10:26 PM about the 2005 Pontiac Grand Prix GT

Question type: Maintenance & Repair

help my 05 gt keeps going to reduced power and traction control off mode. I got codes
p1125 p2120 my machine says the acc position sensor has already been replaced.
Someone tried to fix this problem b4 I bought the car but failed. HELPPPP I don't know
what to do at this point.

11 Answers


I do not that, not until 2006 the bad octane spark table on the PCM was terrible, and would force the car to run in reduced power mode. for the P 1125 IT may be your Throttle Position Sensor, 04 to 08 grand Prix uses a drive by wire system.( There's no Cable to control your throttle, its a sensor on your gas pedal, electronically controls the throttle body) You have a multi level sensor system on your actual gas pedal inside the car. and you have a drive by wire sensor to control your butterfly on the throttle body. I would start with getting that issue addressed, hence that's your only codes your PCM is throwing at you. You can get a replacement at your local auto store for around $100, and YouTube a howto video to install it for free. should take about 1 hour.


I do know that, not until 2006 the bad_octane_spark_table on the PCM was terrible, and would force the car to run in reduces power mode. ( Bad Gas ). Get that Accelerator Pedal Fixed first. The gas pedal will bolt right out of there. Sorry for the typos.

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Best Answer

ok Jae thanks my mechanic is saying the computer is bad the position sensor is new the dealer replaced it recently trying to fix the problem. looks like i might just order a computer there on ebay for 80$


That's odd. The computer going bad is a VERY RARE occasion. Did you run the car through 3 complete drive cycles? ( 3x Cold start, until warm and driving, repeat) ? Also clear all of the fuel trims, and cache by disconnecting your battery for 20 minutes? Before you replace the computer, you may be able to get the computer flashed at the dealer for cheaper than $80. Flashing it will pretty much have it brand new.

Did any of this stuff ever work? I'm having the EXACT same problems with my 2005 grand prix, but don't know if it's the computure, tps, or something else. Email me if anything fixed it. cts3w@mtmail.mtsu.edu


Had this issue with my 04 Grand Prix. When in park, I'd press the accelerator and it wouldn't get past 1300 RPM. When driving, we would have to take off very slowly after a complete stop and even then, couldn't go past 65 mph. Replaced the mass air filter, the computer, and pedal/accelerator position sensor. None solved the issue and the car would still show the "reduced engine power failure" thing. Finally took it to some dude that had a $6k computer error reader thing and it came up with the throttle bottle assembly. After spending money on all this other stuff we said why not, so we went ahead and changed it. It cost a little over $300 at the local auto parts store ao we went to a junkyard/you- pull-it place and found the car we needed. We took it off right then and there. It doesn't take but 10-15 minutes to get out and put back in. all you need is a 10mm socket and git r done!! Sparked up the car and BAM!! We were able to press the gas and it picked up right away. It's been working fine for a small trip now and looks like this fixed the problem!! It was the throttle bottle assembly. When we took the original one out, the gasket was totally worn out and looked pretty ugly. That may have been it but just replaced the whole thing. Good luck!!

1 out of 1 people think this is helpful.

If youfind out what it is plz email me and let me know what it was my car is doing the same thing and they are telling me that is the sensor above my peddal my email is carieo44@gmail.com thank you


Anyone ever above the problem , I have replaced the pedal and throttle body no fix

Ok i need help. My 06 Pontiac Grand Prix base, 6 cyclinder is losing power as i drive and sometimes it dies on the street. One parts store said it has 2 throttle body sensors. I went to a very good friend who owns Napa and there is not a throttle body sensor on that year. I need help. I am thinking it is a accelerator pedal position sensor. HELP


Ok I had the same issue with reduced engine power code and car shutting down while driving. Once I start it back up it accelerates very slow even when mashing in gas pedal. I changed the throttle position sensor first. Unfortunately couldn't get the sensor by itself had to buy entire assembly (took me 15minutes). That didn't fix it so I replaced the accelerator pedal sensor which included the pedal (took me 10 minutes). Problem solved. Not saying it will resolve your issue but it fixed mine!! No mechanic needed don't get taken to the bank. Look up the YouTube video and do it your damn self. Good luck and hopefull this helped.

PLEASE HELP: I have a 08 Pontiac Grand Prix...replaced accelator pedal position sensor and it's still messing up, and getting worse. Car has cut off on me 4 times today. Mashed the pedal all the way down and barely went any where.

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