Limp Mode Issues?

It sounds like a dirty throttle bore this guide can help fix it.

https://www.2carpros.com/articles/throttle-actuator-service

and

https://www.2carpros.com/articles/reduced-power-limp-mode

Please run down these guides and report back.

Thank You...I will check. I will advise if anything changes to keep you hopping. Supposedly, they had the truck apart and checked all connections but you never know.

Another thing that might help for this is to connect a scanner with "record" capabilities, or a type of flight recorder that you control. When the problem occurs, you press the "record" button, then the mechanic can play it back slowly later to see what changed. Because that data passes through the scanner's memory, the recording actually starts a few seconds before you pressed the button.

That is fairly effective with intermittent running problems on older vehicles but for electrical problems it could also affect the power source the vehicle supplies to the scanner. Losing scanner power could erase anything it memorized or recorded. On newer vehicles from the last five to eight years, there are so much electronics and computer controls interconnected, that seemingly unrelated computers can cause the problem you described. Diagnosis of those things can be easier in some cases thanks to all the computers, but when no codes are being set, finding the cause can be real frustrating, as you're finding out.

thanks for the guide I cleaned the throttle body and wow the truck runs great!

Thanks

Nice work, we are here to help, please use 2CarPros anytime.

It is currently raining outside and now vehicle is having engine reduced power showing. Could the rain have any effect?

It might it could be a lot of things usualy turn key off and restart truck it goes away. don't drive through any deep water with that if you did that may be the reason. then have it scanned to see if you have any codes.

Reduced power happens when there is an issue with the "drive by wire" electronic throttle system. It usually limits you to half throttle as long as that light is on. Check for codes as hmac300 suggested and I suspect you will find some throttle codes.

I had just pulled out of the drive way and made it maybe 40 yards before a message came up saying "Reduced Engine Power". The everything was the same and running correctly except for one major thing: the accelerator would not work. I could not give any power to the engine at all. Everything else on the truck still worked as i said, the accelerator just wasn't doing anything at all. I had pulled over and cut the engine, tried again with the same results except it was like that at the start. On the third try everything was back to normal and i drove back to the house and in the driveway it sits. This all happened about 2 hours ago.

You have the same "throttle-by-wire" system that put Toyota in the news a few years ago. There's no simple, reliable, lightweight throttle cable anymore that worked fine for over a hundred years. You have a computer and a multitude of sensors.

https://www.2carpros.com/articles/reduced-power-limp-mode

An electric motor turns the throttle. There's going to be a diagnostic fault code stored in the Engine Computer so it's important now to not disconnect the battery or it will be erased. That information is particularly important now with an intermittent problem.

While driving, the "reduced engine power" light comes on with no pedal reponse. Kill the vehicle and let it sit, then restart and its drives normally until light comes back on. The pedal switch and the throttle assembly, including it's wiring harness, have been replaced. I have loosened and cleaned the grounds for the battery and behind the cylinder head on the left side which connects to the firewall. Also, there is a low level buzz in the stereo speakers; and the automatic feature for the power sideview mirrors, the compass/temp display on the rearview mirror, and the keyless entry remotes work sparatically. I'm not sure what else to try.

have a pro scan for codes for problems other than engine power. check fuses under hood as well.the engine power may be the tac module that is at lh rear of engine compartment. but a pro will need to install it because modules are vin specific.

While driving, everything seemed okay, the reduced engine power message came on and the truck dropped down to a max of 1700 rpm.
New spark plugs 2500 miles ago.
Any thoughts as to where to look?

Check/Replace the Accelerator Pedal Sensor. Check the harness for any wires pulling out of the plug. Also, there are two grounds that can come loose on the back of the block below each cylinder head. I believe they are ground G103/G104. Lastly there have been issues with wires and pins coming loose in the large connector that plugs into the throttle body. I believe the brown and yellow in particular. The part number is PT1572 or GM# 88986255. It is about $100. If that is the case you need to cut and resolder one wire at a time as all the wires are white on the replacement harness. I have heard that GM is not being very cooperative with people when addressing this issue. Hope this helps.

-Pete

engine power reduce. engine light keeps coming on

Go to Autozone its a free public service and have the computer scanned for code/s-you have a problem within the engine management system that caused the CEL to turn on-This is your starting point of diagnosis,finding out what's going on.

I have a reduced engine warning and truck now only idles and won't increase rpm's over 1500, no matter if accelerator pushed down or not. When i went to start it, it barely turn over, feeling like i had a near dead battery, but it did start, then service engine soon light came on, and also it says reduced engine power on message center. Any possible solutions?

get your engines computer scanned immedietely so we can find out what is wrong with it.

may be a tps issue or with the camshaft sensor due to the slow cranking.

get back to me and i can help you find out whats wrong.

thanks for replying blackop555. took truck to the shop and they found that i had a bad battery,which gave the computer grief,inturn giving false codes. replaced battery and serpentine belt,also fuel filter. So far runs normal.

musta been a really bad battery! glad to hear thats all it was and nothing more expensive and time consuming.

im having the same problem with my 03 and it has a brand new battery im sure you will keep having problems because the battery isn't it. I am replacing the wiring harness that leads to my throttle body today and which anyone with this particular problem should do the same.

are any trouble codes being thrown? have it scanned before you go replacing things.

ya i put my scanner on it last week and yesterday i replaced the lead to the throttle body and it runs like a champ.

could you post back the code that showed up that way peopel with a similar problem know what to do when they get the code.

thanks for posting what you found out so far, youve been a help to many im sure.

The subject light first appeared in November 2006. Battery Cables were adjusted and tightened and diagnostic codes were reset. All was fine until this week (14 December 2007) when same light reappeared. GMC service techs now say it is the throttle body that needs to be replaced at a cost of $750. Is this a reasonable solution and cost for the job? Thank you.

Unfortunatly that sounds about right if they diagnosed it correctly.If you are curious call the parts dept on your own and ask for a price on the part, just as a call in customer

There is also a common problem with damaged wires inside the wire insulation of the throttle body wiring connector. You might want to inspect the circuits for an intermittent open circuit.

Good call Denny, forgot about that