2nd Gen Non-Engine/Transmission Do you think it's the PCM?

[mcandies]

Okay, been trying to trace down the problem with my 98 12 valve. Sometimes the gauges become erratic, check engine light comes on, tach and spedo goes crazy, and the transmission disengages. This usually, (but not always), happens after the truck has been running for some time, (5-7 hours). It happens when traveling on a very smooth roads and on rough roads. So far, when it starts acting up, it is usually for brief periods of time, say 2-3 minutes but 3 times it acted up for about 10 minutes. Yesterday I drove 7 hours before it started acting up, at which time it lasted for about 10 minutes then stopped and worked fine for the final hour drive home. (I use it for Hot Shot deliveries)

Things I have done so far:

I have cleaned the pins at the PCM and on the engine speed sensor and put ty-raps on to keep them secure. Checked and cleaned as many grounds as I could find, (4), cleaned both battery terminals and all wires connected to them. Will have the ESS changed this week just eliminate that, (cheapest part to change before the PCM).

My question is; Could the PCM be going bad and causing this or does it either work or not work?

 

[Dave M]

On my 97 I had no tach, gages, alt charge etc and changed the pcm ($600) and then changed the engine speed (or called crank position) senser and that fixed my problem. Cost about $100. Still cheaper than the pcm. And yes it does sound like it could be the PCM or engine speed sensor.



Dave

 

[LMcCary]

I with Dave M, the crank sensor is a likely suspect. Rare that PCM is bad. But it is electronic and can go intermitten.

 

[mcandies]

Well, I had the crank position sensor changed today and on the way home the truck acted up as usual. That rules out the crank sensor. What I noticed the last few times it acted up was if I back off on the accelerator it would stop, (check engine light would go off, gages would return to normal), and when I would press on the accelerator it would go crazy again. Is it possible for the throttle position sensor to cause this?

 

[RLaJeunesse]

I just had the same problem tonight but my fuel shutoff also quit.

 

[RLaJeunesse]

Does crank sensor affect fuel solinoid.

 

[Dave M]

Does crank sensor affect fuel solinoid.

This may be dependent on year. The CPS has nothing to do with fuel solenoid on my 97 but I've heard in 98 they changed and there is an ECM and PCM and the PCM/ECM may control other things.



On my 97 the CPS was bad and the PCM was not working but the truck was running... which means my fuel solenoid was working also. I had no tach, speedo, alt not charging and MIL light not on but all my other gages worked. It may not be so with your 98.