Ok. I wish I could remember the other thread where someone had the exact same issue. No power at PCM and fuel pump was dead. They found a bad wire going to one of the relays, fixed it and everything started working again.

Did you look at the powertrain diagram I posted earlier? Those items are on the same keyed power feed so maybe we just need to find out if there is a broken wire somewhere.

Have you tested the relay with a meter to see if it's working?

I have 12 v-dc at the always live lug then I turn the egnition on and the other big terminal becomes energised

Does the other big terminal go dead after a couple of minutes with the key on?

the manual switch that i put in replaced the original 2 little wires that come from the wireing harnis I taped the ends of each wire and left them to the side and put te manual switch in. Now however I removed the manual switch and re connected the original wires that come from the wireing harnes

I just double checked the New Relay I installed. As I said earlier I returned It to stock and with out the manual relay switch and now the 12V-DC does not transfer to the 2ND big terminal like it is seposto

Can you explain how you wired up the manual switch? I hope you didn't provide power to the signal side of the relay......if so, that would be very bad for the PCM....


Do you still have your old relay? If so, then you might consider removing the relay from ebay and setting it aside for now. Take your AIH relay and put it where your GP relay was. Then put your old relay (the one that you recently removed) in the AIH spot. Wire everything back up like the photo I posted and see if your truck starts.

when wireing the manual switch you put the two bigger wires on the same terminals as the old relay. you put the two other wires to the side. then you put a jumper wire on the relay from theone big terminal that is always hot to one of the little terminals. then you put a wire from the outher little terminal on the relay to a momentary toggle switch and then you go from the other side of the momentary toggle switch to ground.

Ok good. That seems safe. The original wires to the small terminals were left OFF of the relay while the manual switch was installed. Correct?
How did you protect the wires while they were set aside? One of those would have full time power when the key is on...

taped them off

I think this is a good suggestion. Not being able to communicate with the PCM is a major clue.

Have you checked your fuel pump inertia switch? It's located behind the front passenger side kick panel.

yes is ok not tripped

it is not tripped but i reed no power on either one of the 2 wires that go to it

I just we to Auto Zone and bought a new relay. I installed it in the conventional manner and no change. I hane power 12V-DC at the power terminal, Turn the ignition on and no power at the oposimg big terminal.

Take a look at the power train schematic that I posted earlier. You will see that the PCM relay provides power to the gp solenoid, aih solenoid, ipr and fuel pump relay.
What year is your truck? Do you have the second fuse panel under the hood? Try swapping the PCM relay with the blower relay and see if that helps.

Sounds like the fuse to the PCM relay coil is popped.

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