2003 Yukon Reduced Engine Power

[Tatman71]

I have been having issues with my 03 Yukon. Runs like crap, no power and goes into Reduced Engine Power mode frequently. I have changed plugs, wires and all coils a week ago dure to random misfires. I previously replaced the throttle body with a new tps on it and the accelerator pedal module. No change. I borrowed a scan tool and am getting numerous codes. Ones telling me basically replace tps or the app.
I am lost on how to fix it.

 

[Fless]

Welcome to the forum!

Carefully inspect the wiring harness from the throttle body connector back six inches or so; others have had wires that are broken or compromised underneath the insulation. Should be able to flex the wires in your fingers to feel for any bad spots. Also check pin fitment at the throttle body connector.

 

[Sam Harris]

Welcome from Texas! Too bad you did all that work (and spent all that $$), and still don’t have a fix. Hoping the sage advice from @Fless takes care of your issue. Either way, you’re in the right place for whatever help you need.

 

[rockola1971]

Yup. It should be mandatory to replace the wiring pigtail with plug when the TPS is replaced. Its a very well known problem that the wiring harness that plugs into the TPS doesnt hold up well to the natural engine vibration and heat. The wiring in this harness is stranded copper wire and will eventually break under the load of vibration over years of use. Dont confuse the break with an obvious break in the insulation AND the wire itself. Seldomy does the wire actually completely separate itself from the plug or as far back as 6-12" away from the plug. BUT you can usually feel the break if you run your fingers over each wire while grasping with your fingertips of your thumb and index finger. The plug with pigtail is actually a part than you can buy at just about any auto parts store and even rockauto. Thats how common of a problem it is. Then there is the possibility of the TAC(Throttle Actuator Control) module wiring plug partially dislodged from its female socket counterpart OR corrrosion at the plug at the TAC module. The TAC module is between the vac brake booster and fender on the firewall. Its a little black flat box.

 

[MassHoe04]

Timing (pun intended) on this question/issue couldn't be better...

Check out @tomloans write-up. Maybe there is something in there to help your situation.

Reduced Engine Power write-up

Hello all. Thought this might help someone who has had this issue over and over again. The best write up I have seen... Hello all, For anyone reading this old post regarding the numerous years of Silverado's going into "reduced power mode" I will share my findings, hope this helps someone...

www.tahoeyukonforum.com

 

[mwilson62000]

Also check the connectors at the TAC module(drivers side, mounted on the firewall.) On my 03 while running, I could wiggle the 16 pin connector and make it go into limp mode. Ordered a new connector(from LMCtruck.com I think) and spliced and soldered wires to new connector. Didn’t have REP while driving again.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[Tatman71]

Timing (pun intended) on this question/issue couldn't be better...

Check out @tomloans write-up. Maybe there is something in there to help your situation.

Reduced Engine Power write-up

Hello all. Thought this might help someone who has had this issue over and over again. The best write up I have seen... Hello all, For anyone reading this old post regarding the numerous years of Silverado's going into "reduced power mode" I will share my findings, hope this helps someone...

www.tahoeyukonforum.com

I did see that. We had already replaced all the grounds prior to seeing that. That helped rule that out. Thank you for sending me the info. Everyone that has replied has been a big help.

 

[MassHoe04]

I did see that. We had already replaced all the grounds prior to seeing that. That helped rule that out. Thank you for sending me the info. Everyone that has replied has been a big help.

OK. We have some really great diagnostic minds here to check all the possible causes and walk you through steps to identify and fix your issue.

 

[S33k3r]

On our 2005 Suburban 2500, we had water intrusion at/near the ECM. The ECM itself was okay, but the wires leading to it had corroded, cracked, and some were broken.