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  1. #1

    Default ECM-B Fuse Continues to Blow!

    I need help my ECM-B fuse (10 Amp) continues to blow and I need ideas of where to start looking for the short. This is an 89 suburban 4x4 350 TBI.

    The first three times this happened it would only occur when I was in reverse, I would swap the fuse and things would seem to be fine for a while. I took 1.5 hour trip with no problems. I didn't worry much becuase I don't use the truck much and it didn't appear to be a problem when going foward, until today...

    I was on my monthly trip to the municipal yard-waste site when turning in to the drive..bam...truck shuts off. I knew it was the fuse but was worried becuase this was the first time it happened when driving foward. My fears were warranted becuase after I inserted a new fuse it blew instantly when I turned the truck on.

    I went through 3 fuses before it occurred to me that the problem use to only occur in "reverse" maybe the problem is happening in "park" gear position now too. So I shifted to nuetral and tried a new fuse. It worked!! Truck started so shifting seemed to shift or adjust the shorted wire to eliminate the short. But then I went out to shut the hood and the engine killed instantly. So it was a short-term fix and shutting the hood wiggled the wire enough to cause it to short again.

    After the single glimmer of hope that was dashed when I shut the hood, the fuse now blows instantly no matter what position I have the gear shift indicator. I had the truck towed home so I can begin the investigation. But I could use all advice both specific to this problem and general advice for finding shorted wires.

    Becuase it seems related to my gear shift indicator and steering and the general steering column area What major wires could this be? It is the ECM-B fuse..which is the battery feed to the ECM. So whatever wire has the short, it is it is related to the ECM. Does the gear shift indicator go to the ECM?

    All insight or advice appreciated...

    Sincerely,
    Nate
    Last edited by Big6ft6; 04-17-2010 at 08:38 PM.

  2. #2

    Default Transmission Position Switch

    So in looking at my wiring diagrams I see that the transmission position switch is a ground path to the ECM. Has anyon heard of tranmission position switches going bad? If it is a ground path for the ECM is it reasonable to assume that a short in the switch would cause my ECM Battery fuse to blow?

  3. #3
    Jr. Apprentice ecombe's Avatar
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    River Ridge, LA
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    Default

    Nate - I don't have specific advice for this issue, but in general electrical issues are no fun to troubleshoot. I just recently corrected an electrical issue in one of my non-chevy vehicles.

    Sounds like you're starting in the right place by looking at the wiring diagrams. It's a PIA, but disconnect every component on the particular circuit that is shorting the fuse. Then put a good fuse in the fuse box and starting at the rear of the vehicle (longest runs of wire) begin plugging components back in one at a time and check the fuse for continuity between each component plug-in. The component that blows the fuse is the culprit. Then you can concentrate on the wiring for just that component.

    Sorry, I'm not familiar with the '89 burb and what components are on the circuit for the ECM-B fuse.

    Good luck.
    Emile
    05 Suburban LT
    02 Suburban LT
    94 Jeep Cherokee

  4. #4

    Default

    Thanks Emile,

    Now I have a new problem, the short is intermittent, so it seems to come and go with no pattern. When the tow truck dropped my truck off I put in a new fuse and whola! it worked. Then I dirve up and down the driveway...and poof...shuts off again. I can jiggle wires and I've really looked all over and cannot find any wires on exhuast manifolds etc. I climbed up on top of my engine last night and was looking back behind the engine at the main wiring-harness, I see no obvious issues.

    I have noticed on the wiring diagram that the ECM-B fuse seems to be related to the fuel pump and fuel pump relay. I wonder if something with my fuel pump could be shorting? in the tank? I can't quite picture how this would be...but anyone ever hear of something like this?

  5. #5
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    Enkeiavalanche's Avatar
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    Default

    Where do you live? It could be a winter related short somewhere from road salt. Have you taken the fuse block off the fire wall or the one in the motor bay and turned it over to look at them?
    08 Z71 Avalanche Mods to date: K&N CAI,Hellwig Swaybars and End Links, Corsa Sport Exhaust, Superchips Programer,IPCW LOF & 3rd brake light and tails, AMI Gas door,Show Hooks and Door locks, Enkei Wheels, with Pirelli tires, StreetScene Bowties, Grant Steering wheel,Muth signal mirrors,SSBC Big Brake kit,Huskyliner Mug gards,Floor mats and Hood shield, McGard Lug nuts and locks, Bedrug, Cervini's Ram Air hood,35watt HID Fog lights, Sylvania bulbs all around ZXE's Highs and Lows, WhiteNight Back up lights,Sirius and HD Radio, SnugTop sitting on deck now Got a Softopper on now,Tempress Boat Hatches.... New Bilstein shocks are on... New Mods coming soon..... X

  6. #6

    Default

    Thanks Enkei for the idea.

    I have not pulled the fuse panel off the wall yet, I only have one and it is under the drivers-side dash things are very clean and dry there so I can't image there is rust behind it, but I may peek just to see anyway. I have a more dtailed wiring diagram now and it seems the only thing on this circuit are
    1) Fuel Pump Relay Harness
    2) Oil Pressure Switch (which is also a fuel pump switch)

    So I have a smaller wiring path to focus on now, but coming off the fuel pump relay harness is a power line for the "Fuel Pump Prime Connector" which I assume is the main power to the fuel pump?

    I really don't want to lower the gas tank as it has a fair amount of fuel in it..but I may not have a choice.

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