i was reading a post you have on an 02 alero that is very similar to my 03 alero. I only get 5 volts to the fuel pump relay SOMETIMES. It has died on me on the highway once. I have yet to figure it out. When it get hot outside (80+) it really acts up.
Country: United StatesMake: OldsmobileModel: AleroYear: 2003Engine: 2.2 ecotech
Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.
The one line should have 5 volts, as that is for the level sensor, the other line, gray is the one that needs the 12V/
When did you last change the fuel filter?
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When did you last change the fuel filter?
when i turn the vehicle on the fuel pump relay makes a humming noise. when it is making this noise there is only 5 volts to the fuel pump fuse and the 12v line to the relay. (hense the low voltage to the fuse). It seems that there is a section of the fuse block that only has 5v on it. I am not entirely sure if the problem is being caused by the ignition switch or the fuse block itself.
The fuse block should not have 5V so if it does then there is a fault in the fuse block. They are common for failure. Can you manually jump 12V to the fuel pump relay and see what happens.
yeah, if i put the voltage to it, then it starts. i have a GM service manual (I work at an old oldsmobile dealership and we had the old manuals in the attic). I disected the car one day and could not visually find anything. When i put it back together it ran fine for 6 months. I had the PDC out, and the connection for the ignition switch loose. When I had the PDC out I decided to run a jumper from where the power from the ignition switch goes in and soldered fuse to the end of it. My hope was that if it happened again i could put the fuse in the fuel pump fuse location and i could start it. Well it happened on the side of the interstate and putting that fuse in did not work. I could not confirm then if the voltage on the jumper was low though. I am torn between replacing the electrical part of the ignition switch and the PDC under the hood.
The igntion switch does not actually provide power to the fuel pump, so if there is only 5V there then your PDC is bad.
thats what i was afraid of, the switch is cheaper. LOL. So what your saying is the power feed from C2 of the switch is going into the PDC, activating an ignition relay, which is then applying 12v to the necessary parts of the PDC. The 12v power at the PDC actually comes from the direct connection to the battery and the ignition switch just "spreads" it.
Not spreads it but closes the contacts in the relay. If you have 5V on the pin 30 or 87 of the relay then yes, it is direct from the battery. Yuou can always bypass the switch, jump the pink to red and see .
the voltage is low on the fuel pump fuse as well, not just the relay. if that voltage is not supplied by the ignition switch and actually comes from the battery connection that would lead me to believe the PDC has internal issues. From what I can tell on the wiring diagrams the ignition wire directly feeds the fuel pump fuse but I find it hard to believe it can supply that voltage to all six fuses the diagram shows. That is why I am lead to believe that is actually activating a relay in the PDC to distribute power rather than actually supply it. But the diagrams do not support my theory. So I guess I am asking if the voltage for the fuel pump fuse is actually supplied by the ignition switch??? If not then I am definately looking at replacing the PDC. As you know, this is one of those intermittant problems that is always "unable to duplicate" when you are trying to diagnose it so I am resorting to educated guesses.
The power does not come from the igntion switch, it comes from the battery. YOu can test this by jumping the relay pins 30 to 87, that manually provides the connection from the internal buss bar inside to the pump circuit. The relay and igntion switch are only the controll side. The PDC is a common issue on these and I have replaced more than one for this issue
11 years Automotive experience all with Gm.
okay, well I guess that is what I am going to try. Thanks for your help.