help alero fuel pump not coming on

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edward
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Joined: Tue Apr 16, 2013 6:59 pm

help alero fuel pump not coming on

Unread post by edward » Tue Apr 16, 2013 7:40 pm

I have a 2001 Alero 3.4 just to lay out some things I have done when I got it didn't run security light on. I did a fix on the security system by splicing in a resistor inbetween the yellow and black wire going to switch did the relearn and still had some issues checked the switch and it had bad contacts cleaned them and it ran fine but went ahead and but new switch in. Drove car bout 400 miles with a few issues engine light came on abs light came checked codes was rt speed sensor and some emission stuff. replaced rt front wheel bearing it was noisey also and found a broke wire going to that speed sensor , repaired that. then more problems hits some bumps temp gauge quit working and engine light back on next start up temp gauge worked and no engine light. Was heading to work and it died fuel pump not coming on. Swaped relay no change when I run 12v to pump wireing at fuse box it comes on but relay seems to be not working should there be a ground at the location where relay is? I have none. I noticed some corrosion and heard of problems with fuse box so replace it still no change. I can drive and start car with no engine light on if I leave a jumper from one terminal to other. With a known good relay in it wont work on its own the terminal I think is ground for the relay I have 2.4 meg ohm resistance to ground relay has 4 legs at one termial with key on I have 12v one has 5v others have none then the one I hook to that powers the pump I think the other should be ground? been chasings for a week myself took to a trusted mechanic that excells in electric troubles and he is stumped still in his shop now just needing new ideas Thanks for any help i get

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ProTech
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Re: help alero fuel pump not coming on

Unread post by ProTech » Tue Apr 16, 2013 10:40 pm

The PCM completes the relay circuit by supplying the ground path. If you have no ground, you either have a broken wire between the fuse box and the PCM, or a bad PCM.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+

edward
Posts: 5
Joined: Tue Apr 16, 2013 6:59 pm

Re: help alero fuel pump not coming on

Unread post by edward » Wed Apr 17, 2013 12:19 pm

:D Thanks for the answer sounds good to me . I have 2.4 megohm resistance to ground at that termial in the fuse box cant be completly broke maybe corosion. Going to look more for bad wire and if can't find one will try a pcm. If I pulled a pcm from another 01 alero with 3.4 and got the bcm from that car also and put it in mine what chances do I have of it working? I know the pcm is susposed to be programed using my vin. Even if dont run correctly till I get it reprogramed relearn crank position would be ok. My dealer want $120 to program and salvage yard said $30 bucks for the parts Ed

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ProTech
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Re: help alero fuel pump not coming on

Unread post by ProTech » Wed Apr 17, 2013 1:35 pm

If you've got 2.4Mohms on the ground circuit, that is pretty much basically saying the same thing as having infinite resistance and being an open wire. Something isn't kosher on that circuit, whether it be the PCM not grounding it or a wiring/fuse block issue. That would need more checking into and tracing of the circuit.

As for trying to use a PCM and BCM out of another Alero, don't waste your time. First off, the BCM is locked after it's programmed and cannot be used in a different vehicle. Secondly, the PCM, while it can possibly be reprogrammed to your VIN and vehicle, usually ends up not working either.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+

edward
Posts: 5
Joined: Tue Apr 16, 2013 6:59 pm

Re: help alero fuel pump not coming on

Unread post by edward » Thu Apr 18, 2013 6:29 pm

Atlast found the problem traced to the abs unit. I unpluged the abs unit and it found ground , plug it in and short is back. Left it unhooked still no start but fuel pump working tried to check codes and no responce from pcm. Pulled it out it was a reman unit with date of 3 years ago and smelled burnt so opened it up, found melts with discoloration in it. So I wasted my time installed a used pcm from a different car without reprograming to vin. Did the 10 min key on 30 sec off and it fired right up with no engine light, test drove doing relearn for crank sensor. Runs and drives out great trans shifts fine cruise works lock up torque connverter works the abs light is on but hey its disconnected breaking is fine however abs not fuctional. so far everything elese I have checked work. Don't know where you learned that wrong vin pcm would not work. Have you tried it before? Somehow it does on mine so far but only driven 30 miles. Thanks for helping Ed

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ProTech
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Re: help alero fuel pump not coming on

Unread post by ProTech » Thu Apr 18, 2013 6:34 pm

Well, consider yourself lucky because it NEVER works. At least it runs now.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+

edward
Posts: 5
Joined: Tue Apr 16, 2013 6:59 pm

Re: help alero fuel pump not coming on

Unread post by edward » Thu Apr 18, 2013 7:13 pm

I know makes me wonder how long it will. Have you ever heard of abs unit shorting things out? First one my tech has seen do that also with the salvage bcm the raido was locked and air bag light on but car would run reinstalled my original one and radio works again air bag light off. Wonder if I should try the reflash thing or just drive it. Will keep you posted.

edward
Posts: 5
Joined: Tue Apr 16, 2013 6:59 pm

Re: help alero fuel pump not coming on

Unread post by edward » Sat Apr 20, 2013 10:53 am

never say never 100 miles later still going with NO problems with a pcm thats not susposed to work as told on hereand a few oher techs except the tech I use. Just so everybodys knows ground wire from abs hooks into same ground splice that maney other things connect to it was causeing my short and cause the fuel pump to not come on.

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