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redused engine power

Z

zenman400

New member
I have a 2008 pontiac grand prix, and for the last few months i have been experiencing a light that comes on the DLC which says reduced engine power. Right before the light comes on i am on the throttle at a regular pace like in a construction zone following traffic and maintaining speed, but then its like i let off the throttle but i dont then the light comes on then when i try to accelerate its slow and will only go up to 75mph and under full throttle the rpm will sit at just over 3000, when i come to a stop and try to take off it takes almost 20 seconds to engage the throttle to take off and the acceleration is not even there. Also, when i go full throttle at a stop to try and take off faster the throttle will stick and slowly accelerate. Now, i have pulled a few codes if anyone needs them. Thanks in advanced for all the help
 


zenman400 said:
I have a 2008 pontiac grand prix, and for the last few months i have been experiencing a light that comes on the DLC which says reduced engine power. Right before the light comes on i am on the throttle at a regular pace like in a construction zone following traffic and maintaining speed, but then its like i let off the throttle but i dont then the light comes on then when i try to accelerate its slow and will only go up to 75mph and under full throttle the rpm will sit at just over 3000, when i come to a stop and try to take off it takes almost 20 seconds to engage the throttle to take off and the acceleration is not even there. Also, when i go full throttle at a stop to try and take off faster the throttle will stick and slowly accelerate. Now, i have pulled a few codes if anyone needs them. Thanks in advanced for all the help
Click to expand...


Codes will help, please post
 
Here are the codes:

P1516-Command vs Actual throttle position performance, P1125-APP System(both are GM specific), P2125-Throttle/Pedal position sensor/switch E circuit, P2138-Throttle/Pedal position sensor/switch D/E voltage correlation, U0107-Lost communication with throttle actuator control module.
 
Those codes tell the whole problem.

You have a Throttle body issue and a APP issue.

I'd do some diggin and find out which one is the cause and replace as needed.
 
uhm this happend last week to me, you have aftermarket intake by chance? i havent had to replace anything on my car yet its all been bad wires
 


yup, it could be bad wires, the wires at the end of the plug that goes into the tps, take the plug off and inspect them for any cracks bare wire showing, or just missing insulation.

the TB lives right over the exhaust cross over, the heat over time can beat the wire to death.

if you find bad wires it easy enough to cut and solder a new pig tail on.

if no bad wires i would start with a new tps sensor and go from there.
 
well here's the thing I work on semis and trailers i know what to look for when it comes to wiring problems external from the actual harness its self really its hard to say weather its the harness or not without preforming the proper test with a oscilloscope while the event is happening there is no real way to tell but ofcourse i could use a multimeter and measure the voltage out put and compare it to the voltage reference for that system, with that being said i would only do that test if i couldnt find a actual wiring problem
 
just look at them, no real need to go that far. if they are cracked at the end where the plug meets the wires or anywhere else, they get whats known as "dry wire". what happens is the wire turns brown, no longer nice and shinny, and the current does not pass correctly anymore.

if you have wire loom over the wires take it off, stop at the main harness. and inspect those wires to the sensor. im thinking they are like 6 inches long or so from the main harness.

my maf and ait sensors pig tails were so bad i had to cut them both 3 inches from the main harness, due to every time i would strip the wires they were still brown, it wasn't till i got close to the main harness that i got clean copper wire.
 
well i inspected the wires and found all to be good actually they look brand new. Then, i preformed a test with my oscilloscope and found that all is working well not voltage drops at all, so then i did some research and found that the throttle position sensor is inside the throttle body cover plate due to my gp having throttle by wire. Now ive located the problem which is: the potentiometer sensor or otherwise known as the throttle position sensor is getting abnormal or loosing all voltage. The soluation: replace the throttle body. To my knowledge i dont think they make rebuilds for that type of throttle body's.
 


My GTO also has throttle by wire - reduced engine power can ALSO be a pedal potentiometer problem (not just on the TB end of things).
 
I am such a dumbass. So i figured out what has been going on with it. The mass airflow sensor was very dirty and was not receiving or sending good readings. So i cleaned it up and now all is good she is back to normal so all of you out there experiencing the same problem i would suggest getting some mass airflow spray and cleaning up that sensor its a cheap and simple fix
 
I had the same issue with my 04 grand prix and 06 impala. It turned out to be the electronic throttle body. Close to $500 for a new one
 
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