99-02 F250/350 7.3 diesel no comm

[Witsend]

I think I would hook up the battery charger and try my old MT2500 or an old Hickok NGS, crack open a few cold ones and try a Buzz test on myself

[BRIAN617]

Thought unplugging a water ingressed PRNDL switch or ABS module on some Fords would restore communication. Maybe worth a shot.

Bench testing them yields same results

I can eliminate any bad inputs to the PCM this way

[Witsend]

Thought unplugging a water ingressed PRNDL switch or ABS module on some Fords would restore communication. Maybe worth a shot.

[BRIAN617]

do you have more information?. any codes what issues are you getting?
I usually see a p0605 or po603 code with a bad pcm. If the pcm had or has a physical chip plugged into the board at the rear then yes it will still run but have a biased pcm.

This is just simply a communication problem with scanner(s)

Two truck in the last three weeks. However I've also run into it before, seems to becoming more common.

Current truck has valve cover harness problem, and I was able to finally get circuit codes cycling the key a few times to get comm.

Truck before only communicated once or twice. It was a no start, but had crankcase full of fuel. Still I wanted to check IPC psi and % and only got one shot.

Two different scanners OLD Modis and Verus Pro, same results.

Bench testing them yields same results, so its not likely a rubbed wire under the right front seat crazy fix.

[diesel71]

do you have more information?. any codes what issues are you getting?
I usually see a p0605 or po603 code with a bad pcm. If the pcm had or has a physical chip plugged into the board at the rear then yes it will still run but have a biased pcm.

[BRIAN617]

Is there any real good info out there for these PCMs that have hit and miss communications?

Causes, Fixes, Just bad PCMs?

I've benched tested a few with test harness only built for power, grd and comm lines and get same results in vehicle.

Sure makes it tough to diagnose actual engine problems.

Also crazy to have to sell PCM just to diagnose other problems, when the PCM will still run the vehicle.