Reduced Engine Power, reducing my sanity

[John Bragg]

I'm curious is the reduced engine power the sign that the Yukon is ready for the yard??? I have been fighting this issue for probably pushing 2 years now. I have put in mass air flow sensor, throttle body, throttle position sensor, accelerator position sensor, new plugs, new wires, new fuel lines, new fuel pump, and lastly a crankshaft position sensor. Yet still same damn problem popping up. Will this madness ever end? What else could be causing this very irritating and frustrating problem? It's a solid great vehicle and without a doubt the best vehicle I have ever owned, just this one nagging issue that won't go away...is there any help that doesn't involve dropping huge amounts of cash to the "stealership" to get it right. Thanks in advance for any help and suggestions. It's very much appreciated

 

[swathdiver]

Do you have an advanced scan tool John? Without one, you're just throwing parts and guessing. Do you own the shop manual for this truck?

 

[John Bragg]

Do you have an advanced scan tool John? Without one, you're just throwing parts and guessing. Do you own the shop manual for this truck?

Unfortunately no I have a lower to midgrade scan tool, and no shop manual.

 

[swathdiver]

Unfortunately no I have a lower to midgrade scan tool, and no shop manual.

I think we've "talked" before but I do not remember your truck's particulars. You can get a subscription over at AllDataDIY for your truck or buy/download the manual from SeriousCTBuyer on ebay. I use both, sometimes one is easier for me to use than the other but they're kinda redundant as far as the information goes.

Can your tool read fuel trims and transmission speeds and the like? That might be enough to get by. What codes were you getting after seeing it say "Reduced Engine Power"?

 

[John Bragg]

I think we've "talked" before but I do not remember your truck's particulars. You can get a subscription over at AllDataDIY for your truck or buy/download the manual from SeriousCTBuyer on ebay. I use both, sometimes one is easier for me to use than the other but they're kinda redundant as far as the information goes.

Can your tool read fuel trims and transmission speeds and the like? That might be enough to get by. What codes were you getting after seeing it say "Reduced Engine Power"?

The codes it popped up this morning in are P0120 P1515 and P2135. Considering they are all throttle related and I have replaced both the throttle body with sensor and the accelerator position sensor I have been thinking maybe I should replace the pig tail for the throttle body. I have inspected it in the past and done the pull test on it, it did however have some crazy bends and was all twisted and crazy right at the plug. When I did the pull test I removed each wire one by one untangled it from the mess inspected it and did the pull test then and reinstalled it back into the plug. So I am thinking maybe there is a wire with an issue in there since all the codes are related to that circuit. I will look into those suggestions you made information is power after all.

 

[Danny3737]

I’d do a compression test

 

[HiHoeSilver]

I think @Tonyrodz has experience with the pigtail...

 

[swathdiver]

The codes it popped up this morning in are P0120 P1515 and P2135. ...I will look into those suggestions you made information is power after all.

Get your hands on that manual so you can do the circuit tests. Mine does not show the P1515 code but does show the others. Everything points to either bad wiring, bad ECM or bad TB.

 

[John Bragg]

That's what I was afraid of I'm also checking all the grounds some people I have read online had issues with that causing problems. I also have the ABS pump kicking on when stopping but only at less that 5 mph I would say and no light in the dash for that one. Thanks for your help I really appreciate it

Sent from my VS985 4G using Tapatalk

 

[UrbanSuburban]

I think the code that you seen was P1516, I would look after the P120 first as it gets fixed then the others will go away. Its that code that sets the reduced engine power. At least you are not getting the engine off command, as that is the next step in the diagnostic tree. If you have disconnected the TPS you will create some more codes which is probably what the other two are. There are 33 steps in the Diagnostic tree for this code. You need to get the Alldata for this as you are shooting in the dark. You have replaced two items on the list that give cause but still no solution. With Alldata you can buy only one month and that should give you some time to get to the bottom of it. Good Luck with it. As far as your ABS kicking on, that is a bad sensor in one of your wheel hubs, the truck thinks an abs event is happening so it does not activate a code. A scan tool will locate the problem side for you.