Reduced Engine Power on Cold Cold Star and Afternoon hitting Bumps

[mdmcinti]

Hey everyone,

I have a 03 Yukon xl 1500 5.3 with the flex fuel motor. So about a month ago I was driving to work and hit a bump on the highway. I got the reduced engine power message on the cluster and pulled over. After about two restarts everything was back to normal and I continued on my way. I took it to car quest and they read it and I had the P1516 code. Well the previous owner replace the TSP and the the harness with the Forman unit from amazon because they were having this issue. Well this has happened to me a few times and it now seems to only happen on cold cold starts or after I hit a bump. It mainly does this on cold cold starts like at 5 or 6 in the morning. I cold started it at 9 am today and I had no problems, but at 5 in the morning it will do it. When I had it on Mondays cold start, it took may restarts to get the problem resolved. But on Wednesday and Thursday when I started it and had the problem, I wiggles both ground wires on the back of the motor and disconnected the throttle body harness and no problem whatsoever. I am thinking those grounds on the back side of the motor are the culprit because they get shifted by hitting a bump or when it’s cold and the metal connectors and wiring has contacted and not making full contact. Does this sound right from anyone’s experiences? Thank you.

 

[wjburken]

Hey everyone,

I have a 03 Yukon xl 1500 5.3 with the flex fuel motor. So about a month ago I was driving to work and hit a bump on the highway. I got the reduced engine power message on the cluster and pulled over. After about two restarts everything was back to normal and I continued on my way. I took it to car quest and they read it and I had the P1516 code. Well the previous owner replace the TSP and the the harness with the Forman unit from amazon because they were having this issue. Well this has happened to me a few times and it now seems to only happen on cold cold starts or after I hit a bump. It mainly does this on cold cold starts like at 5 or 6 in the morning. I cold started it at 9 am today and I had no problems, but at 5 in the morning it will do it. When I had it on Mondays cold start, it took may restarts to get the problem resolved. But on Wednesday and Thursday when I started it and had the problem, I wiggles both ground wires on the back of the motor and disconnected the throttle body harness and no problem whatsoever. I am thinking those grounds on the back side of the motor are the culprit because they get shifted by hitting a bump or when it’s cold and the metal connectors and wiring has contacted and not making full contact. Does this sound right from anyone’s experiences? Thank you.

Well, these vehicles are known to hate poor ground connections. I would definitely inspect, clean, and tighten any ground connections you can find as well as all your power cables.

 

[mdmcinti]

Well, these vehicles are known to hate poor ground connections. I would definitely inspect, clean, and tighten any ground connections you can find as well as all your power cables.

I did that this morning for most of the grounds and added a new one for the silver strap one on the driver side of the engine. I did not get to the trouble some one on the the passenger side. I took a picture of it yesterday. I could not tell if it was bad or not since it was covered in oil. I am going to see what happens in the coming days.

 

[mdmcinti]

I did that this morning for most of the grounds and added a new one for the silver strap one on the driver side of the engine. I did not get to the trouble some one on the the passenger side. I took a picture of it yesterday. I could not tell if it was bad or not since it was covered in oil. I am going to see what happens in the coming days.

Update. I added another ground from the stud that the TAC module mounts onto the fire wall and ran it over to the stud where the silver ground strap From the driver side cylinder head connects to. I also added one that goes from that stud and gets grounded to the valve cover. I found a random bolt that threads into one of the unused threads on the driver side valve cover. We will see what happens tomorrow and this week when I have to cold cold start the rig at 5 am.

 

[OR VietVet]

I bet you are on the right track here. I have seen so many threads about ground problems. Plus this.

https://www.fixmyoldride.com/Chevro...e7e5cd24ed24635&at_ab=per-2&at_pos=3&at_tot=4

 

[mdmcinti]

I bet you are on the right track here. I have seen so many threads about ground problems. Plus this.

https://www.fixmyoldride.com/Chevro...e7e5cd24ed24635&at_ab=per-2&at_pos=3&at_tot=4

Sounds like a big three upgrade is in the the near future for my rig. It sounds like gm made cheap wiring from the start.

 

[mdmcinti]

Update: It has been 4 days of 5 am cold starts and not a single issue. It’s running much better now. I am glad I got this issue solved and I did not spend any money.