Yesterday it ran fine - this morning when I started it, 3 of the 6 instument gauges are dead and I get no output from the alternator - voltage from the battery is 12.5 volts whether the engine is running or not and the tranny won't shift at all. I didn't find any fuses bad. I have a bad feeling about this. Is this always/usually a bad PCM? Where's it located? I've heard these cost around $600 - $800. Just installed a new rebuilt alt last spring so I don't think it's that. This just sucks.

 

Check The Relays In The Main Fuse Box Under The Hood,check All Electical Connections And Make Sure They`re Not Corroded Or Broke,and Check Your Grounds!!!!if All That Checks O.k.,then You Might Want To Get Your Pcm Checked.good Luck.

 

Crankshaft sensor or wiring. Check the wiring first. Without input from that sensor the PCM does not know the engine is running so the stuff the PCM runs won't work.

 

Well, I checked all the connectors I could find - couldn't find anything that looked corroded and checked all the grounds, went ahead and sprayed contact cleaner on all the connector contacts but it didn't make any difference. A bad crankshaft sensor would sort of make sense - I really, really hope that's the problem, I don't have the bucks right now to pony up for a new PCM (I've heard these are fairly robust and reliable), I'm going through a divorce right now and money and friends to help are few and I really need this truck for just basic transportation at the moment. Just a couple more quick questions though - I think I located the PCM on the firewall passenger side in the engine compartment, is this correct? Also, how do you check the crank sensor? It looks like 3 wires coming from the sensor to a connector with 3 wires that disappear into the wiring harness (checked & cleaned the connector). What voltages do I look for? I really appreciate any help!

 

PM me. Maybe you are close enough I can help out!

 

Sounds like a crank sensor like said before. If the wiring looks good - no cuts or frayed areas, then I would put a crank sensor on it. Easy to replace and a fairly common problem. Check for a 5v reference signal going to it. Other than that you need an oscilliscope to see a wave form, or a scanner to read rpm's from it. Might have a parts store check for codes if you can get it there and back without it charging. Should be fine to drive a short distance, slowly since the trans won't shift!

 

I would say crank shaft sensor. I had the same thing before.

 

There's an Auto Zone about half a mile from here, so I shouldn't have any problems getting it there to have them check for codes - there seems to be plenty of juice left in the batteries. I had thought is wasn't shifting at all, but it does actually shift as far as 3rd gear! I just didn't notice it before because the shifts were so smooth and I sort of get used to looking at the tach. I'll follow up and post what I find out - it is somewhat comforting to find out that crank shaft sensor problems are much more common than PCM problems!

THANKS everyone and thanks vzdude for the offer to help and the advice!

 

Yup, it was the crank sensor - It's back on the road now! Cummins called this part an engine speed sensor - crank sensor maybe refers to the newer engines. As soon as I checked the plug and found the 5 volts coming from the PCM I figured it had to be the sensor that was bad. This forum has saved me from a ton of aggravation and money! Thanks everyone!