I have a 1998 12 valve truck, auto trans. I have a problem was hoping you guys may be able to help me with. While driving, the gauges will sometimes just stop working. They typically freeze in the last registered value. A couple minutes later they will fall to the zero or home position.

I've done some trouble shooting and component replacement with no luck. This is not it a reproducible problem, hence it happens at various times and driving conditions.

The symptoms are The a/c, charging, and overdrive functions also quit working.

This seems typical of a crank trigger failure, but that usually only results in loss of tach and the other fxns listed above. Fixes I've tried include: alternator good, batteries good, tracing wires at PCM to crank trigger, checked all body/frame grounds in good shape, replacement of crank trigger, abs sensor, and transmission sensor, swap a known good PCM from similar truck, cleaned and inspected instrument cluster connections. They all have good source voltage and grounds.

Any help is much appreciated.

 

98 12 valve? Um. That's gonna be fun. You got caught by the transition year....

Is your odometer digital, or are there actual numbers there??

 

digital

 

When your gauges stop working, does the odometer display "No Bus"?

 

No. It just flashes the mileage.

 

Flashing mileage indicates the cluster is not receiving the information it needs. Given that ALL of your gauges are doing odd and strange things, I am thinking that either the cluster, the central timer module (that is what sends all the info to the cluster, as to what it should display), or the wires for communication between the PCM, CTM, and cluster.

If you don't have on already, grab the 01 service manual from here. There are troubleshooting steps in there.