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jcv2118, Chevy Technician
Category: Chevy
Satisfied Customers: 188
Experience:  Gm tech for 5 years, Service Manager at a Chevrolet dealer for 6 years.
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2004 chevy blazer 4 wd ECM1 fuse blows when I put it in

Customer Question

2004 chevy blazer 4 wd ECM1 fuse blows when I put it in reverse. Only does it after engine has warmed up.
Submitted: 2 years ago.
Category: Chevy
Expert:  jcv2118 replied 2 years ago.

hi the fuse is ecm1 or pcm1 ?

Customer: replied 2 years ago.
it,s the ecm1 fuse.
Customer: replied 2 years ago.
what do you think is causing this? I can't find a wiring diagram or schematic of the ECM1 circuit in its entirety to determine all of the units involved with it; but suspect it may be something involving the transmission. Could you e-mail me the diagram?
Expert:  jcv2118 replied 2 years ago.

you think you can fix it with the schematics for this fuse ?

I can send you that.

Customer: replied 2 years ago.
Not sure; but this looks like a difficult problem at this point. Would appreciate the diagram so we can both be trying to find the problem. Thanks. (*****@******.***)
Expert:  jcv2118 replied 2 years ago.

ok I will send it over in a few.

Expert:  jcv2118 replied 2 years ago.

ok I wont be able to send it until later this afternoon, is that alright ?

Customer: replied 2 years ago.
That's fine, thanks. What puzzles me is that it won't do it with a cold engine. Just after it has been driven. As I recall it has done it twice while driving in forward. On a very rough road going down the mountain. Pretty scary freewheeling down about two miles with no power steering or brakes, lotsa hairpin curves. But that was the only time it did it in fwd. Fuse is guaranteed when I drive it to town and get hemmed in in the parking lot where I can't get out in fwd. As soon as I put it in reverse it blows.
Expert:  jcv2118 replied 2 years ago.

Here is the diagram ?

Has any work been done lately under the car, muffler, trensmission etc ?

Are your engine mounts broken ?

My guess is a harness is shorting out when the engine moves because of the transmission being put into reverse. It should be grounding out near the exhaust since it does it mainly when its hot and the chaffed wiring if any is most vulnerable.

Customer: replied 2 years ago.
Good thoughts, raining here very bad with hurricane on the way. Will check mounts when I can get it under cover. Just in case it isn't then I'll run a new wire to the power train control module as this looks like the most possible - where would the PCM be located? Thanks for the schematic and your input - believe the info should take me to the problem. Dave
Expert:  jcv2118 replied 2 years ago.

If I had to bet I would go for the engine harness contacting the exhaust at some point in the car..the PCM is very unlikely to be the culprit