98 Tahoe ECM/Electrical Issue

M2Q

MEMBER
1998 CHEVROLET TAHOE
V8
2WD
AUTOMATIC
210,504 MILES

I have a 98 Tahoe, 210K miles, inop because it is blowing ECM-1 fuzes. Vehicle wouldn't start after letting it sit in a parking lot for a bit; thought it was the fuel pump (again) but when checking the relay I noticed the ECM-1 fuze was blown. I changed it and turned the ignition on and the fuze immediately popped again. Any ideas before I start tearing the wiring harness apart? No OBD codes are available because there is no connectivity with the ECM.

Thanks

3 Replies

CARADIODOC

MECHANIC
33,737 POSTS

Use a pair of spade terminals and jumper wires to plug in a 12 volt light bulb instead of a new fuse. The bulb will be full brightness when the short is present. A head light bulb is a good choice for this circuit. It will allow a maximum of up to about 5 amps to flow. Now you can unplug things until the bulb becomes dim or goes out. There are four plugs on the Engine Computer. Those are a good place to start although it's unlikely something inside it would short just from sitting. You can also remove relays to see if the short can be removed that way. Look at the fuel pump relay in particular. After that, you'll need a service manual to see what else is on the circuit.

Caradiodoc