Question about 1999 GMC Sonoma

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20 amp ECM B fuse

In the black box under hood there is a 20 amp fuse labeled ECM B. I was told it is tied to the fuel pump and computer. Earlier this summer it kept blowing the fuse, I would replace it and be on my way. Afew days later it would blow again, so I ask one of your experts what it could be. I was told it was a short in the fuel pump itself. I put it off for awhile knowing it was a big job. Got tired of blowing fuses so Finally I changed the pump. All went well and I have driven the truck 4 or 500 miles since. The other day it blew again, only this time, it will not take a fuse, it blows right away. Any idea's?

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  • shep111 Oct 27, 2008

    Thanx drcool.....I will try that.....may take some time, the plug is rater hard to get to with tank installed but after I check it I will accept the answer or have another one..thanx again.....shep111

  • shep111 Oct 28, 2008

    goodmorning everyone, I posted this question yesterday and drcool gave a logical answer,but unfortunately after I unplugged the fuel pump and tried to replace the fuse, it blew again. Any idea's

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Dear,

check the the injector connecter wires if they are brittle

regards,

Posted on Oct 28, 2008

  • SALMAN NASEER Oct 28, 2008

    dear,
    if that doesnt work then it could be the internally shortage of fuel pump.
    The fuse ecm b it tied to the fuel pump, PCM, and VCM. 

    regards,

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Go through the wiring inch by inch and look for a spot that is shorting to ground.

Posted on Oct 28, 2008

  • AbdulRahiman S Oct 28, 2008

    ECM B fuse supplies a constant 12v (hot at all times) to the VCM/PCM and to the fuel pump relay. The fuse is blowing telling you that there is a direct short to ground somewhere. Try this, take the fuel pump relay out and put a new fuse in. If it doesn't blow put the relay back in and if it blows then try a new relay. The relay may be shorted to ground internaly. Other wise you'll have to trace the wires to the VCM and the pump relay to look for a chafed wire that's contacting metal. The wire coming from the ECM B fuse is orange and has a splice in it going to the pump relay and the VCM/PCM.
    Hope this helps......

  • AbdulRahiman S Oct 28, 2008

    You might check in the the compartment where the fuel pump relay to see if you have another relay that is the same that runs something else. You could swap them and see if it's really the relay before you order one and have to wait on it.


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Check all wiring and componenets in engine

Posted on Oct 27, 2008

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Check the orange wire that runs between the ecu b fuse and pin 20 on the blue connector of the ecu for a short or a contact.

Posted on Oct 27, 2008

  • Ginko
    Ginko Oct 27, 2008

    Check also the fuel pump relay, take ut the fuel pump relay from the box and crank. If it blows the ecm b fuse , then it is the fuel pump relay.

  • Ginko
    Ginko Oct 28, 2008

    I told you, I guess you could not read my solution.
    I repost here :

    Check the orange wire that runs between the ecu b fuse and pin 20 on the blue connector of the ecu for a short or a contact.



    Check also the fuel pump relay, take ut the fuel pump relay from the
    box and crank. If it blows the ecm b fuse , then it is the fuel pump
    relay.


    Test ECM with a code reader.



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Check again the fuel pump. check the resistance if too low. or unplug the pump and put a fuse again, if the fuse will not blow, then the pump went bad again.

tnx 4 using fixya,

drcool

Posted on Oct 27, 2008

  • francis rivero Oct 28, 2008

    ok..tnx 4 the update.

    well if it is an ECm fuse, then let us start with the ECM,
    unplug the wire to the ECM and test again if the fuse would blow.

    if it would still blow,theni think you better get a test light because you would end up consuming a lot of fuses that would be breaking up. if you know how to use a test light, then i would suggest that you trace the wires from the fuse for grounding.

    the wire going to the ecm and fuel pump could be grounded.

    tnx again for using fixya,

    drcool


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dear,


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Fuel pump could have an internal short
check it by the way...

regards,

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