All Gmt900 Owners Should Read This: Mbec Fuse Blown

[07max]

All GMT900 owners: TSB - 3075

 

 

Symptoms:

 

 

MBEC (60A) fuse blown in engine compartment fuse bay

 

No Passanger power window

 

No Power seats

 

FIX:

 

 

Check the wiring harness between parking brake and firewall for wear/short

 

Story:

 

Tonight when I rolled into the driveway (I usually park in the street) I set the parking brake (normally don't do this) and shut the truck down. I went to roll up the windows (sorry 75 deg. in so.california today) and nothing from the passenger side. Tried the rear window, nothing. Power seats, nothing. I tried all the fuse locations (none of them have a label for the power windows by the way). I started looking on the internet and found a TSB related to the MBEC breaker under the hood. Sure enough if was blown (60A no less). As we all know it's not easy to blow a 60A fuse. There was little else on the internet and I didn't want to pay Alldata for the TSB detail. After searching around I started wiggling the Pbrake. I heard a relay firing somewhere and the lights would dim for a moment. I could hear the short under the dash. I moved the fuse panel to the right of the Pbrake and heard the shorting shound again. Finally I found the culprit. There's a large wiring harness coming from above running between the firewall and the release for the Pbrake. There is a flange where the release cable terminates. That flange is cutting into the wiring harness. I can see the wire tape cut through and at least one wire with copper exposed. Nice wiring job GM. The harness is tight and really can't move that far out of the way. All this after I was cursing the guys who installed the dvd headrest system, myself on the brake controller install, etc.

 

My truck is an '07 so it's taken less than two years to cut into the wire. All NBS Silverado owners (and likely all trucks on this platform) should inspect that harness. I'll take some photos tomorrow when it's daylight.

 

I guess now is a good time to get the washer fluid heater recall completed, the rear-main oil leak fixed, etc.

 

 

Steve

[Porter_]

good read, thanks for the info. i set my parking break every time i turn the truck off. might be cutting through the wiring harness pretty quick here if my truck has the same problem.

[Spurshot]

Steve,

Thanks much. Look forward to the pix. I don't use the P-brake much but the riding condition sounds like it may cut the wire bundle anyway.

 

Are you going do a dyno/in-person tune with Justin when he comes out?

[weymard]

 

Thanks for the information, I use always the park brake ! I am waiting your pictures !

[longhorn_giant]

I also use my parking break every time I stop the truck. Looking forward to your pictures, and I'll have to check it out this weekend.

[eyeball03]

Thanks for the heads up..waiting for the pics too!

[07max]

A photo of the location:

 

This did not turn out great - I was in a hurry. I'll take some more later. The red arrow shows the flange I am referring to. The wire damage is visible if you pull on the brake release lever. If you look at the firewall under the dash (drivers side) up-to-the-left of the brake, that's where were talking about here. The silver plate is the spring cover for the parking brake.

 

[07max]

Steve,

Thanks much. Look forward to the pix. I don't use the P-brake much but the riding condition sounds like it may cut the wire bundle anyway.

 

Are you going do a dyno/in-person tune with Justin when he comes out?

 

I would love to meet Justin. I can't say enough about the tune. I'm a computer guy by day so I love being able to tweak things. I pulled a 6,500 pound boat with the tune in tow/haul mode (0 TM) 400 miles and the truck did great. I'd say there even more improvement towing than around town....but maybe I'm crazy. I think Justin has been in Temecula, CA which is about 1 hr away - but I missed him.

 

-Steve