rollin_coal89

Ok so my trucks tach will work when i crank it for a couple of min then jump all over the place then quit altogether. Which in turn takes away OD, and she quits charging. Sometimes the check engine light comes on when this happens sometimes it don't.

NEW PARTS:
*CRANK SENSOR(gapped properly)
*TPS
*BOUGHT PROVEN WORKIN PCM

Speedo works on and off, also sometimes when i turn my key forward the check engine, wait 2 start, WIF, and trans temp lights dont come on. In turn meens i cant pull codes.

Please fellas help me get my ol girl lined back out, thanks it advance!!!

Ol gal is a 95 2500 built auto, HX40, runnin no fuel plate, AFC full forward, 1000 ohm resistor in place of trans temp sensor.

patdaly

When you replaced the crank sensor, did you happen to clean out the connector good with contact cleaner and blow it out ? Oil can get in there and cause an intermittent shorting condition. Check that out, and after that, it just about has to be a broken/shorted wire in the circuit.

This is from a 97, I will have to look and see if the 95 is the same, but it will get you started.,

rollin_coal89

Ok traced all wires found no nicks or cuts of any kind. Which wires are the power wires for the PCM? Or rather how do i test the PCM. Packed crank sensor full of dielectric grease and still no change

On a side note, since i have that hx40 on the ol gal i have yet to get my downpipe....... So do you think the heat coming outta the exhaust side could b enough to damage the PCM? It is covered in some soot too... Safe to take a hose and rinse it off????

AlpineRAM

I would suggest that you take a multimeter and check the supply voltage (should be 5V) to your crank sensor.
A short to ground in the +5V part of the PCM can drop the voltage so far that other sensors can't be read by the PCM.

So, before throwing parts at it, go and measure.
If your sensor voltage is below 5V start unplugging stuff like the water in fuel sensor etc- if it comes up you know what you just unplugged grounds out your pcm sensor supply.
If nothing changes, start wiggling the wire loom.