I'm having trouble pulling codes off the EECM. I have no CEL at key on. So, obviously it doesn't flash when I install the jumper from the STI to pin 2. And even if I use a test light, from battery positive to pin 4, I still get no flashes.

I have read that this could mean that the EECM could be bad, but I want to check the wiring. Does anyone have a pin out that would work for me? 90 302 Manual 4x4

I have 5V at the STI, but pin 2 isn't a good ground, I guess. Because if I ground the STI straight to battery, I hear relays clicking after the fuel pump primes.

Thank you, and I will also accept any other diagrams you feel like posting. Haha.

 

You can pull the codes by grounding the STI to the battery neg or a good ground. You do not have to use pin #2.
We say to use pin #2 only because if it works you know the ground path is OK through the PCM and back to the NEG post of the battery.

1990 F-series.


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Thank you for the pinout subford.

So, what you said makes me think something is wrong with pin2's path to ground. If it does go through the EECM to ground, then its definitely bad.

Sorry to ask for more, but do you have the rest of the diagrams for the truck? So, I can check all the pins in the test connector. And all my other sensors for that matter.

Thanks again!

 

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Thank you!