Forced Idle Commanded. No throttle response, wrench light and a laundry list of codes.

Since most average joes dont have access to PTS for updated Wiring diagrams i will help with a fast diagnosis.

Heres the only electrical gizmos you will need.
1. A pair of dykes.
2. An old light harness for like a license plate light.
3. a spool of wire.
4. Random hand tools.

Okay so this truck i had was at a bunch of different dealerships and it never got fixxed. It was an intermittent problem. Its had a throttle pedal installed its had a new engine harness and new FICM harness installed as well as a new EGR valve and fan clutch hub. (none of these components are cheap and this truck was out of warranty)

So the codes that i received and none of which pertained to the component at fault, were for the EGR valve, accelerator pedal, fan clutch, etc etc. So first things first, find out what the circuits have in common. Whether its reference voltage or signal return lines. Beings it has a brand new harness eliminate a possible harness issue, BUT its still possible for the harness to have rubbed through. So all you have to do is a load test, unplug the PCM connector and all the connectors that are in common with the circuits.

Apply 12v to the sensor and at the other end install your light bulb see if the light illuminates bright or dim. The end of the circuit was the pedal. beginning was the VREF wire on the pcm harness side. had another tech look at the bulb and yes it was dim. So 1 by 1 working from the pedal to the front of the circuit found the EBP sensor shorted out. and again there was NO EBP codes either. TO verify this, unplug 1 sensor at a time until it has a pedal key off disconnect sensors 1 at a time (but plug them back in if that one didnt cause a change) until the wrench light goes out. thats to make it even faster than using your light bulb to load test the circuit....

customer spent a grand total of over 6000 dollars and is going for legal action.

 

Hey Bill, a quick question for you. If you had a scanner on it and were specifically watching the EPB sensor PID, would it show anything abnormal? I'm assuming it would right?

I actually had my wire harness chaffed through on two wires of the three total going to the EPB sensor on my truck... no codes, turbo would fall on it's face once in overdrive... literally, boost fell to 0. I could roll into it and leave a trail of smoke miles long, until the truck downshifted, boost would shoot back up and it'd clear out. Started watching it with AE, and watched the sensor go from min to max and back to min over and over again, checked it out and found the chaffed wires... taped it up and it ran fine after that.

I was just curious if in your case it would show something too? I'd imagine it'd be like finding a needle in a haystack, since no one would think to look for the EPB PID and monitor it, but just curious on your thoughts.

Thanks for sharing, that's a good idea. Could you send me those wiring diagrams by chance? Or would that be a PITA? Anyway I could convert it to PDF or something and upload it here? That'd be awesome.