2003 Chevrolet Avalanche Logo
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ralph mcgruder Posted on Mar 28, 2014
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Blown fuse pcm

My pcm fuse blows when i turn on the ignition but if i take out the fuel relay switch the pcm fuse does not blow what could be the problem

1 Answer

Bill Boyd

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  • Chevrolet Master 53,816 Answers
  • Posted on Mar 28, 2014
Bill Boyd
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Joined: Jan 04, 2013
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It is possible that the fuel relay is faulty and causing excessive current through the pcm fuse which is blowing because of the excessive current draw to the relay.

  • Brett Cirbo Mar 29, 2014

    First, begin with the basics. Shut EVERYTHING that is un-necessary, OFF. Install a new PCM fuse and then turn the ignition on to the RUN position. Does the fuel pump activate and charge the system? If it does, and the fuse has yet to blow, then the fuel pump can be eliminated as a power drain or short. // If the fuse did blow, then look towards the ignition switch to start. GM is not famous for good quality ignition parts. Disconnect the primary connector to the ignition module and try again. This should differentiate between the ignition switch and the ignition module. A fuel pump failure is possible, but highly unlikely. I would suspect the ignition or a bad ground before a fuel pump failure.

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5 Related Answers

Anonymous

  • 11 Answers
  • Posted on Aug 14, 2008

SOURCE: 1996 chevy s10 will not

check the crankshaft sensor

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Anonymous

  • 3 Answers
  • Posted on Jan 25, 2009

SOURCE: no power to ignition 96 camero dl

Check the wires to the distributer or to the modules could be poor or no conection. If you can turn the car over but no spark it's probably something to do with ignition, distributer, module, or wiring to the ignition.

Anonymous

  • 21 Answers
  • Posted on May 25, 2009

SOURCE: blowing ignition a fuse

I believe you mean a 40 amp fuse? Wow! that's a dead short somewhere on a large wire. Could be difficult, or hopefully easy to find. There's always the smoke test option: Solder a jumper wire across the top of the fuse, making the circuit essentially un-fused and look for the smoke. Not the best method, but quick. Warning: if you do this, depending on where the short is, you could melt down the wire harness or possibly start a fire. Try this at your own risk! IT'S A "LAST RESORT" THING, WHEN YOU'VE TRIED EVERYTHING ELSE AND FAILED! Good luck.

Anonymous

  • 224 Answers
  • Posted on Jul 11, 2009

SOURCE: 94 chevy s10 blowing fuse

Chances are, you have a short somewhere in the wiring that is causing too much amperage to pass through the fuse causing it to blow. Use a decent voltmeter that will show opens and shorts to test continuity with the wires that run to the ignition.

Anonymous

  • 10 Answers
  • Posted on Aug 05, 2009

SOURCE: fuel injecter fuse blow imeditaly when ignition turn on

sounds like a short in the wiring from the fuse and the fuel injector junction block. GM like most fuel injection systems control injector firing by the computer providing ground to each injector in pairs or individually. The fuel injector fuse provides power to the injectors using splices therefore enabling one wire to feed 6 injectors. A shorted wire at any of these wires will blow the fuse. On one rare incident I found a faulty computer caused the fuse to blow. A shorted injector will just cause a rough running problem due to the injector stuck either open or closed.

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Those vehicles use an integrated power management module that holds that relay and several other parts and they can go bad. You have to replace the whole thing.
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There is no reaction when turning the key to start the car

Turn key to On.
Turn on headlights manually... Do they come on?
Are there any lights on the dash?
If yes to these, battery is possibly not the sole problem.
Check for good, tight and clean connections at battery terminal posts!
If yes to above, continue on & get a helper... Turn key past on, to Start position.
Do you hear a click sound at time key is turned to Start?
If yes, then ignition switch is not problem, starter relay is getting power, and is now sending power to starter, but starter is not working.
Pic any No's... Then look there.
Good luck.
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fuel pump is bad,your relay will be also from trying to start pump.there is an outside chance your relay is bad,easier to change that first
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I did look at power distribution wiring diagram for your vehicle, I found pcmB fuse--20 amp. Two fuse legs goes to pcm, the other goes to load side of fuel pump relay. If I had to guess, I'd say the fuel pump has a problem. If the wiring before the fuel pump relay or the pcm was the problem, then the fuse would blow as soon as soon as you plug it in. The fuse circuit shows to be hot all the time. Just my opinion. There might be other issues, but, I can't track it from where I am.
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