Solution to Reduced Engine Power Message and p1516. Look Here

[Tonyrodz]

It’s holding up great. I put 10k plus miles on my Yukon after I found the root cause of my reduced engine power. It has not come back and it’s been almost four months. The truck is sitting now since it decided to have a lifter spin/collapse back at the end of December and take the cam with it. It runs fine and doesn’t miss, but it has horrible lifter knock and so it is parked until I get some money together to fix it this spring.

Yes, I think the throttle body does not ever fail and I have a Forman sensor on mine. I would check the wiring from the pigtail to the plug because those tend to come loose. The. I would check all the ground. The two big ones are on the back of the motor and they are pita to get to unless you have the intake manifold off. Also doing my grounding trick would help to. I kept all my grounds on for the heck of it since they were not hurting anything. Also the TAC module never fails either. It’s all in the wiring. I was also reading that it seems like 2003 is the year that seems to have this issue and some guy on another forum found that the wiring harness for the pedal and the tac module have a smaller gauge wire compared to a harness and pedal he took out of a 2004 plus truck. So GM fixed it with thicker wires on the later trucks.

I hope you figure out the problem I kept getting p1516 with this problem. Good luck!

I sporadically get that Tac and pedal sensor codes on my 03. I just clear the codes.

 

[mdmcinti]

I just got lucky and figured out that whoever installed the aftermarket pigtail harness didn’t do a good job crimping the connections. It took a little bit of trial and error, but wiggled the pigtail to cause the error code.

 

[OR VietVet]

Success!!!!!!!!!!!!

 

[clemenshess97]

Just did my ground wiring couple of days ago ,like in the youtube video (neg bat ->throttle body module ->firewall -> generator -> pcm), also cleaned the grounds near the front bumper and the two on the frame under the drivers door, replaced throttle body and replaced the pigtail connector, it worked for a few days.
But today I got P1516, P1518, P2108, P2135, also the doors unlocked and the ABS light came on, I cleaned the codes and it ran good for about 5 miles, then got P1516 again.
Does anyone have a idea what I can do ? add more grounds (from where to where) ?...I am kinda desperate now as I‘m driving to Denmark in three weeks and really want to get this problem fixed before heading on the Autobahn.

 

[rockola1971]

It’s holding up great. I put 10k plus miles on my Yukon after I found the root cause of my reduced engine power. It has not come back and it’s been almost four months. The truck is sitting now since it decided to have a lifter spin/collapse back at the end of December and take the cam with it. It runs fine and doesn’t miss, but it has horrible lifter knock and so it is parked until I get some money together to fix it this spring.

Yes, I think the throttle body does not ever fail and I have a Forman sensor on mine. I would check the wiring from the pigtail to the plug because those tend to come loose. The. I would check all the ground. The two big ones are on the back of the motor and they are pita to get to unless you have the intake manifold off. Also doing my grounding trick would help to. I kept all my grounds on for the heck of it since they were not hurting anything. Also the TAC module never fails either. It’s all in the wiring. I was also reading that it seems like 2003 is the year that seems to have this issue and some guy on another forum found that the wiring harness for the pedal and the tac module have a smaller gauge wire compared to a harness and pedal he took out of a 2004 plus truck. So GM fixed it with thicker wires on the later trucks.

I hope you figure out the problem I kept getting p1516 with this problem. Good luck!

Oh the throttle body "sensor" (TPS) does indeed fail. I bought my 2005 Yukon Denali at a discount from a car lot because it would go into limp mode immediately after leaving the parking lot and getting off idle rapidly during a test drive. I lowballed the used car place and told them I would take it as is and fix it myself. There were worn dead spots on the TPS. I replaced it for like $100 and works great ever since. Another fairly common problem is the wiring harness going to the TPS. It will get wire breaks a few inches from the plug causing intermittent open of a wire and loss of signal. In fact its common for the TPS to come with a new plug with wire harness that can be spliced to replace the OEM one. All cause immediate reduced power limp mode. All apply of course to drive by wire setups.

 

[clemenshess97]

I just realised I could make the engine go into limp mode and throwing all the codes by wiggling the small ground wire on the passenger side of the engine, turns out the wire was replaced already but the connection was made very poorly so it made the engine go into limp mode whenever I hit a hard bump. I cut the wire off and connected a new ground from the harness to the alternator bracket.
The terminal where it used to connect to the engine was still in good shape, but I wouldn‘t want to take this risk of this failing in the future, therefore I ran it to the alternator bracket, makes it easier to maintaine the grounds.

conclusion: new ground wire from battery to throttle body module, new ground wire from throttle body module to firewall, new ground wire from firewall to alternator bracket, new ground wire from alternator bracket to the PCM, new ground wire from the throttle body to the alternator bracket, new ground wire from engine harness ground wire to the alternator bracket and a new throttle body.

The amount of grounds are crazy, I know...but it runs fine now and doesn‘t throw codes when hitting hard bumps.
Maybe this helps anyone who is experiencing the same problems with his truck.
Good luck!

 

[OR VietVet]

So many times on these rigs intermittent or head scratching electrical problems are fixed by just doing something better than what the factory did.

That is why the Big 3 was thought of and developed: https://www.tahoeyukonforum.com/threads/another-big-3-upgrade-with-questions.111196/

How To: The Big 3

www.gmfullsize.com

 

[Monkeywrench78382]

so how has this been holding up for you? I am going to be diving into reduced power issues with our 03 denali soon. figured I would start with this type of thing before I start dumping things like throttle bodies and such at it. mostly because I am cheap!

Better bring your A game patience you're gonna need it, been fighting this issue for several days now, 750.00 in parts 12hrs of my time still unresolved. Sooooo mad almost set mine on fire! gonna see if I can find some answers if not just gonna dump it and it can be someone else's headache.

 

[bigdog9191999]

Better bring your A game patience you're gonna need it, been fighting this issue for several days now, 750.00 in parts 12hrs of my time still unresolved. Sooooo mad almost set mine on fire! gonna see if I can find some answers if not just gonna dump it and it can be someone else's headache.

Have ours solved for now. I started by adding several grounds just to be sure and because I had the parts so money was not a factor. But was unfortunately no change.

But it did end up being the tps, and swapped the tb and it fixed the symptoms. A few days of relearning and it hasn't driven better I'm some time.

Now is going to be on to oil pressure sending unit, and some o2 sensors.

Another reduced power thread 03 denali

well as the title indicates, having issues with reduced power on or 03 denali. I haven't done too much with it yet, but pulled some codes. a couple that I knew where there, and a couple that surprised me a little, but not too much if there is other electrical issues. guess it is time to get...

www.tahoeyukonforum.com

 

[Tonyrodz]

Mine randomly came on last week for 3 consecutive days when starting it in the am. It hadn't came on in a long while after cleaning the ground under the ds running board. I reset it each time and it was fine after that. It had those 3 common codes set too.