2nd Gen Non-Engine/Transmission Electrical puzzler

[upf7flyr]

'95 Dodge std cab, w/ #6 cam plate / exhaust brake / heavy ex springs / 3000 rpm gsk. 5 spd trans. 2 wheel drive.
Having an interesting electrical prob. First, it's intermittent, which doesn't help. The Tach 'dies' and when it does, the "Check engine" light comes on..AND the "Wait to start" and the "Water in Fuel" lights also come on. I'm not sure if
these lights STAY on while the tach is "dead" or not.. ( It happens while I'm driving). Is it Crank speed sensor?.. Doesn't seem likely. PCM loose connection(s) ? More likely? WHERE IS the PCM? I have the factory manuals, and can
see the wiring, etc. but not very good at this. Any ideas where to start would be appreciated.
Thanks
John G.

 

[upf7flyr]

I just learned something else about my intermittent prob. It's in the 'failed state right now and the alternator isn't charging, (volts remain at about 11-12v after starting), and the air pre-heater isn't cycling like it normally does after starting a cold engine.
The "Check engine" light and the "Wait to start" and "Water in Fuel" lights never came on when turning key to "on" position, (prior to starting). My PCM is on the firewall, (in the '95) and the connections 'look' good. Found no bad fuses so far. Thanks in advance. John G.

 

[BarryG]

I had a bad cps in my 01 (cam position sensor as it doesn't have a crank sensor like yours does) and I got a bad tach and it ran a bit rough with a cel and a code but other than that it was ok or at least did not notice anything else out. . I have also had a funky ecm that did effect the wait to start light and the grid heaters. If I disconnected my batteries for a little bit it would reset the ecm and all would work well at least for a while as time went by it got to the point and of course it was in the winter time that I had to disconnect the batteries some mornings to get the truck to even start as it would need the grids to get started. Again outside of the wait to start light and grids it ran fine other than that.

 

[GAmes]

These multiple electrical issues are very often due to corroded ground wire connections, and there are a bunch of them. Cleaning and some dielectric grease might be all you need. The FSM has pictures of where all the connectors are. Plan on several hours.

 

[JStoll]

agreed on the ground issue... you can also run an extra ground from the engine to the body and from there to the negative battery terminal.... you can also use a DMM and check for ground drop setting the DMM to volts DC and paralleling any ground circuit with the probes... the voltage you see is what isent getting through the resistance in the circuit... you do this circuit loaded meaning with engine running and loads/consumers on...
when the alternator stops working do the ground drop test from the alternator case to the battery negative... if you see like 2 volts its a ground problem... it could just be a bad alternator too... try thumping it with a hammer (not too hard) while its in fail mode... if the symptoms sudenly stop its a bad alternator for sure
take care
JAK