Electrical problem
 

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.

Attachment 30560

Attachment 30561

Attachment 30562

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?