Anybody had "PCM Reset" problem?

[Doggy Daddy]

I have a problem on a '99 F250 that I have found described in TSB 97-15a as PCM Reset. The truck acts like the key has been turned off and back on quickly: the WIF, WTS and SES lights cycle and the accelerator returns to idle until it is released and reapplied. The problem happens more when the weather is cold (OK, in western WA terms cold; about 30 degrees overnight) and the truck has been driven for about 6 miles. It seems like it occurs when the cab warms up, that is about the 6 mile mark where the heater needs to be turned down. It never sets any codes.

The problem does not always happen, which is making it hard to find. When it happens is usually when trying to accelerate slightly, like up a slight grade or leaving town and getting back to hiway speed. The truck cuts out like the key was turned off, I release the accelerator and press it again and it usually will have the failure a few times in a row once it starts happening.

I first thought that it might be loosing power or ground to the PCM and hooked up LEDs on those circuits. The LEDs never blinked while the problem was happening (although as I talked about it with a friend he reminded me that an LED will operate with less voltage than the PCM needs). Then I found the TSB (97-15a) that describes the symptom exactly, except that it says that the problem could be a power/ground problem as I thought, or shorted sensor or IDM/injector wiring issue. WOW, that pretty much narows it down to the front half of the truck!

Anyway, since the problem is so intermittant and I have not been able to catch it happening when I have the opportunity to check it, I was hoping that somebody has had this experience and could tell me how it turned out for them. I could just start replacing things but wouldn't know that it was fixed until it happens again. Have you heard of it?

TIA!!

 

[jharvey]

Does sound like a loose connection somewhere, I'd start with the IDM and PCM connections and make sure they are good and tight. Actually disconnect them and make sure they are clean and re-attach.

Oh yeah make sure your battery connections are tight as well (don't ask how I know what happens when they aren't )

 

[Doggy Daddy]

I had looked at the connections at the PCM and Power Distribution Center early on. Everything looked good then, although I have not looked at the IDM connector. I have ohm tested the sensor circuits and short-tested (connect one end to fused power, ground the other end and see if the circuit is good enough to blow a fuse) the power and grounds. I have access to a Snap On Modis and tried to record the failure but did not get the correct page going on the tool the last time the problem occured, and since then it has not acted up. Also installed a break out box and put a 4 channel scope on the ICP, EBP, MAP and BARO hoping to see that something has gone to ground, but the symptom has not occured since the tools have been connected.

I am hoping to find someone that has had the problem and been able to resolve it just to get an idea where to expect the problem. As it is now it could be any of the sensors, any of the connections, the wire harnesses, or the IDM (it already has a different PCM and the problem has happened since then).

I just can't find the connection between the temperature and distance driven and load applied. I am kind of suspecting the ICP since it changes when the acclerator is applied. But then it seems like when the cab warms up which could be the BARO sensor, which is supposed to be under the driver side dash although I have not found it yet (the illustration in the TSB is of 94-97 OBS truck). and the way it is after a certain amount of driving seems like something on the Backpressure/Warmup function. Or maybe it has nothing to do with those things and is just a coincedence.

I definately welcome any feedback!