Thread: No power to fuel pump relay from PCM? *Update issue resolved*

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  1. #1 Re: No power to fuel pump relay from PCM? 
    GT Level Member RegalGS98s's Avatar
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    Fuel pump relays? If you have someone turn the key to on, do you have power at the fuel pump harness for about 3 seconds? Where is pin 8 of the PCM supposed to go? What was the original condition before you changed the fuel pump (Did the pump go out unexpectedly, were you working on something else when it stopped working, etc.)?
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  2. #2 Re: No power to fuel pump relay from PCM? 
    GXP Level Member txslow6's Avatar
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    Copy and pasted from another forum:

    Vehicle in question is a 97 Pontiac Grand Prix GTP. This issue has me scratching my head.

    A little background on the issue:
    Before installing the new fuel pump the vehicle would lose power(like fuel was cutting out). All accessories would still be active. I assumed the fuel pump was going bad as one day I tried to start the car and it wouldn't. Fuel pump wouldn't prime so I ordered a new one.

    Got it installed and was still seeing the same issue. Took the fuel pump back out and double checked everything. It all checked out and went to try again-Same fuel pump won't prime the system. And I have no fuel pressure.

    I began to diag the electrical. First was the fuel pump fuse since it is hot at all times-checks out) Next wents to the fuel pump rewire(bypasses the fuel pump resistor which is a known problem in the GTP's). It's getting the full voltage to and after the fuse all the way back.

    Checked the fuel pump relay and replaced it to be on the safe side.

    I went ahead and forced the pump on manually by giving it power and it kicked on. Tried to start the car and it didn't(haven't checked the fuel filter but that will be later).

    Went back to checking the relay and found that it wasn't getting power at the pins on the fuse panel. No problem let's check the continuetity and power. No power to it at all. Checked for power at the wire off of the PCM and no dice. Went ahead and checked the pin off the PCM and still not getting power. Then checked to see if I'm getting 12 volts at the PCM supply which it is.

    I found out the BCM cuts the fuel signal to the PCM if it doesnt registers, and theft deterant relay does as well.

    Next step was to look at the BCM(body control module) which sends the signal to the PCM.

    No shorts on the pins of BCM. BCM will initialize, but is not sending the 5v pulse for the fuel cutoff. Tried to pcm with same results.

    I also pulled every fuse to see if something is blown and all are showing good.

    The Drivers Information Center is blinking 0. I also have tried using a 2nd known good PCM and it does the same. I even tried hooking a scanner to the vehicle to pull codes and it won't connect with either PCM. I tried the scanner in a different vehicle and it connceted just fine.
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