New to the club have problem with ECM fuse keeps blowing?
89 K1500 ECM fuse will blow when I put 10 or 15 amp fuse in. When I put a 20 amp fuse in it will not blow. Installed a New Crate GM engine 5.7, Transmission rebuilt 700r4, rebuilt rear end 8.6 10 bolt 3.73 Ratio. Installed new ECM, ESC, knock sensor, Temp sensor, Oil pressure sensor. It'* running good but worried about 20 amp fuse? I did the work myself. I've been looking for a crimped wire all ground straps are new, clean and sanded where the ECM grounds at the thermostat housing bolts. Any help would appreciate.

I'd start disconnecting things until you find the short. You may be asking for trouble with that fuse.
Here'* wiring diagrams.

Thanks for the response, I should note that 10 or 15 amp blows when driving and not all the time when riding around town. Idling in the shop it want blow. Just wondering when it goes into over-drive is that blowing it. Off work for a few days will take it back out to see if I can find exactly when it blows. ..and THANKS for the wiring diagram!

Since it doesn't use a TCM but the ECM handles the tranny it could be the TCC solenoid may cause a problem.
You have a scan tool? If so, you can watch it.

Yes I am looking into that, replacing motor, trans and rear end it could be anywhere. Will take out and drive it in 3rd gear see if I can get it to blow? If not put it in OD see if it blows. Thanks will keep this post updated till I find the short. Thanks again.

What scan tool will work? This is a OBD-1. Thanks.

GM has a data stream for this. Any Tech I type tool will read it.

I just had a thought:

How old is the battery?

What are the conditions of the battery cables and grounds?

How old is the alternator?

Maybe put a real volt meter on it and see if it is running around at a low system voltage. Low volts equals high amps equals blown fuses.

Thanks for the reply: Battery is new, alternator has been in there for awhile at least 12 years. Alternator voltage is 13.85.

Moved thread from the "Chevrolet" forum to the "GMC/Chevrolet Truck/SUV" forum.