No power to fuel pump relay?

Tiny
THE1NONLY
  • MEMBER
  • 2004 GMC SAFARI
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
I'm looking for a wiring diagram for the vehicle listed above. I am dealing with crank runs then like 2 seconds later. I thought it was probably a pass lock issue, but I tried the 30 minutes relearn and didn't change. Fires right up then seems like fuel pump isn't working. So, I was trying to jump the relay but like a rookie I accidently jumped 86 to 30 and it sparked not no power. To the relay not constant or when turn the key. So, I'm assuming I blown something, hopefully a fuse. But all the simple fuses look fine. Where should I start to look?
Monday, March 27th, 2023 AT 10:51 AM

4 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,513 POSTS
All of the power leads for the fuel pump relay come from the PCM I would check the fuses ECM -B and ECM -1 for power on both sides here is a guide to help. The fuses are under the hood in the main fuse panel.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the images (below). Please let us know what happens.
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Monday, March 27th, 2023 AT 11:56 AM
Tiny
THE1NONLY
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  • 8 POSTS
Thank you! Okay, so, I did what you said and found blown fuse replaced it. Got power back to fuel pump relay, I jumped it correctly with in fuse wire this time (should of the first time lol) pump turns on and stays running. Tried to start it while bypassing relay but still just shuts off right after startup. To me sounds like it's the stupid pass lock system. Because with everything else working fine it must be shutting off injectors due to the pass lock, right? I haven't tested the power to the injectors yet but even if one or more was not working the van wouldn't just shut off it would run badly, right? I don't want to have to text info if not necessary, it looks like there kind of hard to reach and probe. I have tried the pass lock relearn but maybe I missed something? Any ideas?
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Monday, March 27th, 2023 AT 1:43 PM
Tiny
THE1NONLY
  • MEMBER
  • 8 POSTS
Also, when trying to do the reset my security light comes on the first turning to on position then goes out a second or so later, then comes back on and stays on. No matter how long the light doesn't go out. In the reset it says it will blink stay on then go out after ten minutes and then turn the key to off position 10sec back to on until light goes out again reapt. Etc. But mine just stays on. I even left it on for over an hour because I heard will reboot or Sumin after left in position for hour. Supper frustrating, I've been without a vehicle for over 6 months. My buddy's mom lends me this extra van she has. We drove it up to Washington from OR. No problems, gas gauge doesn't work so you just have to estimate mileage. I fig it was getting low since the last fill up but was super tired, so I parked it at home instead of getting gas that night. The next day came out and the battery was drained because the stereo got left on, I think. And it's done this no running thing since then. I went and put like 4 more gallons in tank just to make sure wasn't out and still just does the start and shut off. Just some more info on the back story. If it helps at all, lol. I originally thought the security got tripped cause of the drained battery maybe, but this is my first GMC and pass lock nightmare, lol.
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Monday, March 27th, 2023 AT 1:54 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,513 POSTS
I need to ask, does the security light flash or does it go out? If you could make a short video and upload it with your response, I can tell what's going on. You may have another issue that has nothing to do with the Pass lock system, I just want to make sure we are going in the right direction to fix the car.
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Wednesday, March 29th, 2023 AT 12:07 PM

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