I have a 96 12 valve and my tach doesn't work, no charging system, and the transmission won't shift out of second gear. I have been told that the pcm is bad. I have read that the pcm is also the most unnecessary replacement on that year model. I have also read that my crank sensor could be bad. Is there any tests I can do to make sure I don't have to fork over. 400 bucks for a pcm for nothing. Thanks in advance.

 

If your voltage is below 12 volts the PCM won't work but here are a few checks and some ideas.

To check the PCM do This : disconnect your crank sensor, turn the key on, check the harness side Blk/Lt Blu wire for ground (low Resistance). Check PPL/Wht wire for 5 volts DC. If these check good chances are your PCM is fine.
To check the sensor do this; check resistance at Crank sensor pig tail (Unplugged still) between PPL/WHT and Blk/LT Blu should be some resistance showing and not a open circuit.

Here are some schematics to help you out.

1996 engine schematic1.pdf

1996 engine schematic2.pdf

1996 engine schematic3.pdf

 

Thanks for the reply. I'll have to try that out this afternoon when I get in from work. I'll repost after.

 

I found my problem right off the bat! The plug for the crank sensor had vibrated loose. However, now I can drive it, but when I go to stop, my transmission won't shift itself out of gear. I have to shift it into neutral and then back in drive. I pulled the pcm out at one point. Could that have caused it? At one time there was a lockup switch on the truck but everything has been disconnected. TIA

 

Anybody?