reduced engine power light

Asked by Jan 24, 2014 at 12:07 PM about the 2005 Pontiac Grand Prix GXP

Question type: Maintenance & Repair

I have a pontiac grand prix 2005 the reduced engine ligh comes on (mor so in rain) the car
will not excelerate above 30 pmh or so and the it will completley stall out. Usally if I wait
10 to 15 mins it will start again. took to my machanic one code was for the gas pedal
/exelerator i can't recall what they said other issue could possibly be.traction lighjt also
comes on. VERY flustrated please help/.

20 Answers


If you're losing power during rain showers, the first thing you will want to do is replace your plug wires. Is your vehicle skipping a lot? If so, it's a spark issue.

4 people found this helpful.

30 mph is a clue. The ECU might be putting your car into "safe" mode. This happens when the ECU senses a catastrophic engine or transmission issue that needs attention. The fact that it happens in the rain leads me to believe that the plastic control box that houses the electronics is not sealed tight for some reason. Have the mechanic check the OBD again while someone mists water over the box. Don't use a garden hose. That said, these cars are prone to steering column harness issues. I'm betting there were a lot more codes than just pedal position. Check the ECU box first.

2 people found this helpful.

I had reduced engine power then my cruise control stopped working. My car eventually stopped starting. I popped the hood and realized multiple wires were being shredded by a belt. Separated the wires and everything works fine now!

4 people found this helpful.

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!!

11 people found this helpful.


2 people found this helpful.

I had the same problem with my 2004 Grand Prix. It had 2 codes P0068 and p0101. I tried cleaning the MAF sensor and throttle body and changing the fuel filter, but continued to have the same issue. After inspecting the MAP sensor, I noticed that it was in 2 pieces so I replaced it, unplugged the battery for 30 min. and it appears to be cured

4 people found this helpful.

I'm sorry , I forgot to say that the reduced engine power and service traction control lights were both on, and the car had gone into limp mode. I was beside myself, I had no idea that one sensor could cause so many problems.

5 people found this helpful.

I think I have the answer to the problem theres a relay I ur ignition that pulls power and causes your reduced power to come on that's what the dealer did to fix my car and I think that if you move your key around in the ignition or play with your key pull it and jiggle it around that what the problem is its your RELAY hope this help anybody out there

5 people found this helpful.

I drive an 04 Pontiac Grand Prix, I've always had issues with my traction control lights coming on. Then I started getting the "reduced engine power" and my car wouldn't go over 20 mph. It coded at p1518 so we took off the throttle body and it was black. Cleaned it and put it back on, then ran 2 cans of "sea foam motor treatment" through the intake while holding the gas pedal down and keeping it at 2000 RPM and the light hasn't come on since. Runs like new.

1 people found this helpful.

How did you clean the throttle body? What was used. My car is doing exactly the same thing.

1 people found this helpful.

I cleaned the throttle body with throttle body cleaner, but the problem occurred. It wound up being a missing o-ring on the bottom of the egr valve. I had this car for 10, and absolutely loved it. Unfortunately It wound up getting an engine knock, so I bought a new equinox. Good luck

I'm sorry but it was not the EGR valve, but the PCV valve, that I had had problems with. the O- ring was not put in on the bottom of the valve which created a vacuum leak. Funny, because it passed smog with flying colors and didn't start giving me problems until about a month later. Good luck, sorry about the wrong info. at first.


I have a 2004 Grand Prix gtp supercharge reduce engine power comes on stabability control traction control an car just shuts down I use to can go over 60 then 40 now I'm in park an I have to check before I pull off because the car will shut down lose power an the wheel will lock up what's the problem I just put a new battery in is the motor locking up at a certain power or is there an computer glitch Plz help

5 people found this helpful.

Vershaun, did some research and here's an answer that I found that may give you a good place to start: The GTP uses a fuel pump resistor to control current flow. This resistor is bypassed during cranking but kicks in once the car starts. So when this resistor craps out, the car will start but then die out because the pump loses power. It is located behind the washer bottle on the right side of the car and stinks to get to. Replace this resistor and happy motoring. PS You can verify this by hooking up a fuel pressure gauge when the condition happens. You will see an initial pressure of 38-40 psi and after it starts and the condition occurs, you will see the pressure fall quickly. The car will stall at about 25psi. Just a note, this above solution was on a 2000 GTP. The resistor may not be located in the same place on your 2004.

1 people found this helpful.

Richard would that have a similar effect on a 2005 G6? apologies


Danny, I didn't find any info for a 2005 G6 fuel pump resistor so I will have to say the G6 doesn't use one like the 2004 GTP.


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.

1 people found this helpful.

I am having the same issue, I went to the hobby shop that we have, I had to put a new axle boot on my passenger side axle, The car ran and drove fine, I put fuel into the car, "same fuel I always use never an issue" and about 10 miles later, the display center said Engine power reduced, and the car started misfiring, and I couldn't give it much gas even with the accelerator down pretty far. The car is parked now, So I will head back up there and go through some of everyone's suggestions. Any other advice would be much appreciated! Thank you, - John

1 people found this helpful.

Same thing happen to my Pontiac Grand Prix 2004 I put fuel into car and immediately as I started it engine power reduced light up, MinnesotanJohn did you find out what to do, other comments scare me , they say a lot of bad things happen when this light flashes , holla back need your feedback.

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