P42 stuck in 1st gear

[FishPlug]

I have a postal service surplus 2003 Workhorse P42 with 6.5 GM diesel and 4L80 trans. Won't shift out of 1st. No Speedometer, no odometer, ABS light. Replaced both speed sensors. Checked fuses. Starts and runs great. Two repair shops couldn't pull OBD codes. Lots more boring details, but any advice?

[Ultra RV Products]

Sounds like a failed DRAC module. I would contact these guys: https://udmodule.com

[FishPlug]

Thanks. Ill check into the DRAC

[Soppy]

If you can't pull the codes , you have a communication problem . The problem could be the PCM or the ECM and TCM modules depending on your configuration. I would start by checking the connectors.

[FishPlug]

Will do. No lack of connectors on this rig. Thankfully the P42 service manual has already been posted on IRV2. Chapter 6 - Engines is 5,004 pages. No excuses for troubleshooting the problem.

[FishPlug]

No idea what PCM, ECM or TCM look like. I don't see any loose connectors anywhere. My hazard lights don't work either.
Attached an OBD2 and got PO113 - intake air temperature Sensor 1 Circuit High Input. Doesn't seem to relate to my stuck transmission.
Also, can't seem to attach pictures to these posts.

[catmandoo62]

that intake air temp could prevent it from locking up the converter,but shouldn't bother on the gears.the ecm will be an aluminum looking box about an inch and a half thick and about 8 inch square with 2 or 3 big harnesses into it on one side,might by under the engine cover right behind the radiator,my 99 winnie is on a bracket in front of and above the drivers side valve cover.do your turn signals work?if so you could just have a bad flasher on the 4 ways.

[FishPlug]

All the connections to PCM, TCM etc. appear fine. Disconnected, sprayed contact cleaner and reconnected, but no change. May throw a few parts at the problem - ABS module is what one mechanic predicted. DRAC unit has been mentioned. PCM? Months ago I did have a dragging front caliper and rotor that got red hot. Replaced the caliper and all good, but maybe the heat damaged the wheel speed sensor for the ABS. The wheel speed sensor seems to be built into the the wheel spindle, not accessible externally. I think it would show on OBD-2 scan, but no OBD scan works, so back to the likely computer problem.