PCM gone crazy ?

[91PDXmocha]

So last sat driving home from the bank and the car dies, no fuel. No fuel pump prime or whine so I get car towed home. check inertia switch and fuel rail.

cut hole for fuel pump and check pump, with the ecc pin grounded the pump runs with the key on .

next go to ccrm , swap ccrm for another m code and now all that happens when you turn the key the fans come on and you cant check the engine codes.

I checked all the wires and found a rubbed spot in the fusable link from the pos bat cable to the 2 yellow wires feeding the ccrm ? I cut it back and hooked it up directly for now.

I put a meter onto the ground wire coming from the pass side to a plug then to the pass fender and also attached to the bat ground. it was not making good contact so I took the wire out and hooked up directly to it. I also notice here that the ground wire coming from the PCM side has .5 volts on it with the car key off.

now when I got in the car to try and start with the key to on the fans come on but looks like check engine light came on ( not just dim ) But also noticed smoke starting to come from the pcm ground plug I had hooked up. so key off.

with the ccrm unplugged and the ground to the PCM I can read .5 volts on the #5 pin of the ccrm harness and also .5 on pin what 13 that is the FP ground .

Also with the good ccrm plugged in the check engine light stays on ALL THE TIME bright, like even with the key out of the car .

So I have a new fuel pump and ccrm but no new computer. Sounds like my computer is fryed and there is a short to ground somewhere in the engine harness to the PCM ???

Ive read as many old threads as I could find on it and checked everything . Any other ideas before I plug in a new computer and pull the harness ?

Thanks

 

[shopartsnw]

Try unplugging your coolant level sensor and then fix any burned up parts. See if that changes anything.

Mike

 

[91PDXmocha]

Thanks mike , I did unplug the sensor and have truer tracing all the wires. I'm going to pull the battery and check all the wires again , but I'm worried about plugging in another computer and blowing that one :/ I hate electrical problems .

So I just want to verify . The fuel pump and PCM should not have the .5 volt coming off the ground correct . Pin 5 should be 0 with the key off right ?

 

[shopartsnw]

When I have seen the coolant sensor go out, it keeps the computer/fuel pump from working, but I have not had it blow the computer (just the fuse). If you replaced a fusable link with a hard wire, you may have defeated the fuse function and damaged the computer, but I would try your old computer first to see if it survived.

Mike

 

[91PDXmocha]

Put everything back in the car , new ccrm old computer and now the car starts up and will run but within 5 sec or so of having the key turned to on the pcm ground wire and the fuseable link start to smoke . Im going to add a inline fuse on the FL wire . It does this with the fuel pump unplugged and fans unplugged too. Good to know the parts are not all fryed but still bummed .

 

[91PDXmocha]

Ok ive found the shorted wire. The white/purple wire that goes into the fusebox #1 and #6 meets the big yellow ignition + wires, is fryed. Going to start ripping it all out and see what I can do to fix it.

 

[Toolman]

Glad you found the possible cause. Keep us updated!

 

[91PDXmocha]

Well That was one fryed wire fixed that one, and now testing the + battery lead unhooked I traced the ground as far back as the black/org wire coming off the solenoid . It feeds 3 fusible links , blk/org , yellow and black yellow I believe . Looks like they all go into behind the dash . I've started ripping the dash out . Have removed the whole column and most switches . Still grounded out somehere .

Does anyone know where exactly those 3 wires go to next ? I thought yellow goes to ignition switch , no idea on the rest so far .

 

[91PDXmocha]

Turbo SHO is alive back on the road. The short is in fuse 8 , interior lamps,stereo and such. I have that disconnected and put everything else back in and she fires right up now wierd stuff no CEL. Im gonna find the shorted wire over the next few days while swapping in the black interior