I'm in the midst of troubleshooting/verifying the Electronic Spark Control (ESC) module on my '91 5.7L. My Haynes manual shows most of the truck's wiring, but not the ignition circuits. Can someone provide a link or point me in the right direction to find the pinouts and color codes to the ESC module and the distributor? I have found a few write ups online, but a schematic or diagram would really be handy.
I've learned this much so far, by tracing wires with an ohmmeter.
ESC module wires: (It is a 5-pin connector, but only four of them are used.)
A - Dark Blue
- (this may be the ESC "bypass" control line) - goes to ??
B - Dark Gray
- This is Ground - goes directly to the engine block at an intake manifold bolt.
C - Yellow w/blk tracer
- (This may be the wire that provides the REFERENCE pulse from the ECM; Used to trigger the ESC module to do what it does. That is, advance or retard the spark.) Goes to ECM (computer), but I failed to log the pin #.
D - Pink w/blk tracer
- Goes to 12-pin ECM connector at location #5 on the top row. As near as I can tell, this is a switched +12 volt output from the ECM. There are only 23 ohms between this pin and pin #1 of the same connector where +12 volts comes into the ECM.
E - No Connection
If anyone can fill in some of the blanks or provide additional info on the ESC circuit, I would appreciate your help.