Ok I need some real indepth help here. I seem to have a broken connection in my coolent temp circuit (PCM coolent temp circuit). The connection is broken where the PCM taps into the circuit to fetch it's reading. Does anybody have a clue where this patch is made? (I've got a 1994 Z28).

There has to be a separate power source performing the voltage division. Then the PCM A/D converter taps into the line for it's reading. It would be nice to see a schematic of this circuit if anybody has that as well.

I traced the line back to the big hunk of wires at the rear of the engine compartment and about passed out. Your help in locating the PCM tap location would be AWESOME!

Thanks for the help!!!!!!!!!!!!!

 

Don't know what you mean about a "patch" . The yellow wire from the sensor goes directy to C25 of the PCM. The black (ground) side goes to a common point (splice somewhere in the harness). If you have disconnected the C connector from the back of the PCM and metered the yellow wire to prove that it is open, then you just need to expose the wire from end to end to find your problem. There are no shortcuts for that type of problem.

 

Oh ok sweet. Just what I needed to know. They must do the voltage divisions & 5v power in the PCM. I know a little too much for my own good. I disigned this shtuff in me own time as a computer engineer. Just don't have too much practical hands on w/ regular cars.

I've got one more question. On your site you have the cooling fan switch mod. W/ that switch... is it supplying 12v to the C100 connector pins H, and J? Or is it grounding them. I not to firmilar with that type of switch.

Thanks for your help shoebox... your the fbod god!