2007 GMC Sierra 2500 HD Classic, bone stock LBZ motor with 225,000 miles. Truck ran great until it had a front end collision 8 months ago. When the truck came back it started to have issues. We are now experiencing limp mode, reduced power mode and it is throwing a code P0106 for 5V Reference 3 circuit low voltage. We have had it checked and one mechanic said it was either the Turbo Vane Sensor, MAP Sensor, EGR Valve or Accelerator Pedal Position Sensor. We changed each of those with GM Parts and nothing changed. We took it to another shop that worked more on diesel trucks and they told us it was the ECM and that it wasn't communicating with the truck. We sent the ECM off to have it checked and repaired and were told that the ECM is fine. Put it back in and still same issues. I have checked and cleaned all the frame grounds on the truck, removed the fuse box and checked for cut or pinched wires or anything out of the ordinary and cant find any issues. The next step is to replace the ECM but I am not sure that is the issue. We have replaced the TCM as we thought that was the issue at first since the truck would go into limp mode but that did not fix anything. Has anyone had issues like these? We cannot seem to figure out why the truck will go into Limp Mode or Reduced Power Mode. When it happens you can turn the truck off and let it sit for a few minutes and most of the time it will reset and drive ok for a while before it happens again. Totally lost as to what to do next.
Bake199
You need a wiring diagram to figure out which wires are on the circuit that is low. That usually means there is a supply voltage problem. Once the circuit is isolated, you will need to load test, breaking it down onto sections for testing. A simple test light doesn't always show the problem, you need to load test it with at least 4 to 5 amp load.
It could be something as simple as a broken wire that separates when it heats up, or a connector with bad pin fitment or corrosion.
With the front end damage, a wire could have been stretched and not completely broken or a connector crushed.
It can be very frustrating trying to find these intermittent problems like this.
Good luck.
It could be something as simple as a broken wire that separates when it heats up, or a connector with bad pin fitment or corrosion.
With the front end damage, a wire could have been stretched and not completely broken or a connector crushed.
It can be very frustrating trying to find these intermittent problems like this.
Good luck.
I had this same issue and had a bunch of mechanics look at it and they couldn’t find the issue. So I took it upon my self and looked at all the wiring and sure enough I found a wire that at first glimpse didn’t looked frayed or cut but it was. Ended up finding a bunch of wires like that and soldiered all of them back together and it fixed the issue.
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