06 F-250 intermitent dead pedal, wrench light

Mekanik · June 8, 2012

I’m working on a 2006 F250 with an intermittent wrench light and a dead pedal. Initially I had a slew of DTC’s. P0069 for the baro sensor, P0404 EGR range fault, P0472 EP low input, along with a bunch of other AP DTC’s. I was able to determine that I didn’t have enough vref voltage-1.7v to be exact. I checked it at the baro sensor which I unplugged and then I unplugged the EP sensor and checked it too. It was 1.7v, but shortly after I checked it there it came back to 5v. I wiggle tested the wiring, inspected for chaffed wiring with no avail. The circuit that provides vref for the baro also supplies vref to the AP sensor, so that explains the dead pedal.

The customer ended up taking the truck and had the same problem. Now I’ve only got a P0472, two AP DTC’s-P2138, P2139, and a P2285. Of course I wasn’t able to get the problem to act up. I’m thinking a couple different things here. First, what if my EP sensor was shorted? I could see that causing the PCM to shut off vref. But then I did have 1.7v and every time I’ve seen a scenario like that my vref was 0v. Also I did unplug the EP sensor and measure 1.7v vref at the connector, but can I really expect my vref to come back to 5.0v instantly? I’m not sure. Then I was thinking maybe I have a chaffed harness, possibly the circuit providing this vref.

Has anyone run into something like this?

Keith Browning · June 9, 2012

If we consider all of the input devices relative to your post you need to look at the EVTM and discover that there are two VREF circuits involved between them all. If you could verify the low voltage on both VREF circuits it would point toward a bad PCM... PCM power or ground fault.

Mbl35 · June 9, 2012

I have once on an 08 e350. I got stuck on a test drive a few hours after posting about it,. The vref circuit was the cuase. Drove me nuts. Wound up replacing harness.