Engine/Transmission (1994 - 1998) 1998 12 Valve Gauges Stopped Working

[98 Dodge]

I have a 1998 12 valve truck, auto trans. I have a problem that has been a real challenge I 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, along with all gauges stop working, 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 voltage 14.2-14.3 volts, batteries good 12.3-12.4 volts, tracing wires at PCM to crank trigger with no breaks, checked all body/frame grounds in good shape, replacement of crank trigger with correct gap (set at 0.050"), abs sensor, and transmission sensor, swap a known good PCM from similar truck, cleaned and inspected instrument cluster connections, checked PCM connections and seated good. They all have good source voltage and grounds.

Also, to add no codes, no CEL. After the problem occurs, I cannot talk to the PCM when I connect a OBDII scan tool. Its like the PCM has shutdown on an overload condition or something. I have to perform the reset/diagnostic check by holding the tripometer for 10 seconds with the key switch and then connect the OBDII scan tool. No codes or pending codes are present.

Another note is, if I let the truck run for 10 or so minutes before I start the trip it doesn't seem to happen as often.

Any help is much appreciated.

 

[BigPapa]

This may not be related at all, but just for grins and giggles, check the three connectors on the fire wall right above the master cylinder. Make sure they're not corroded and that they're snapped together good.

When I swapped my 12V into the 98.5 I had similar issues and it ended up that one of those connectors had not been snapped together all the way.

 

[98 Dodge]

Thanks for the advice. That is one place I haven't checked. I'll try to post later and update on progress.

This may not be related at all, but just for grins and giggles, check the three connectors on the fire wall right above the master cylinder. Make sure they're not corroded and that they're snapped together good.

When I swapped my 12V into the 98.5 I had similar issues and it ended up that one of those connectors had not been snapped together all the way.

 

[The patriot]

I'm taking a jab in the dark because I ordered mine with the correct trans(5 speed) but maybe the TPS?

 

[DRAG DIESEL]

I have been diagnosing mine for a couple years now. It has been EXTREMELY intermittent. I think I have found the solution, will report back as soon as I get my answer. Mine only acts up when the ambient temp is on the higher side. My hypotheses is that only the auto trans trucks are going to have this problem. I have 2 PCM to test now, one is CA and one is FED.

 

[Missouri Mule]

Did you check ground for the Engine Speed Sensor (you mite be calling by different name). When the ESS goes bad or has wiring problems you lose the voltmeter gauge,overdrive (no rpm readings to gauge or pcm), and when the ess ground is bad you lose a/c. If it is the ground all you need to do is run a remote wire to the ess. Unfortanately my 96 factory service manual is not going help you. Your going to have to look at a 98 FSM.

 

[Missouri Mule]

Did you check connector on the back of gauge panel to see if it was secure.
Re read your post seems to pointing to the PCM.