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So if I'm reading that correctly, I should have 3 wires going to the black EEC test connector: Pink/Lt Grn, Tan/Lt Grn, and Black/White. The White/Red wire goes to the gray STI.
Did I get that?
I'll go back and verify the wiring colors in the black connector. Either the PO plugged the STI into the larger EEC connector, or something strange has happened to my wiring.
(More context on that: most emissions stuff has been removed and connectors are just laying there, but I don't get any CELs.)
So if I'm reading that correctly, I should have 3 wires going to the black EEC test connector: Pink/Lt Grn, Tan/Lt Grn, and Black/White. The White/Red wire goes to the gray STI.
Did I get that?
I'll go back and verify the wiring colors in the black connector. Either the PO plugged the STI into the larger EEC connector, or something strange has happened to my wiring.
(More context on that: most emissions stuff has been removed and connectors are just laying there, but I don't get any CELs.)
Thanks!
Actually, four wires, because there are two pink/light greens.
Here's what's on the back of my EEC plug:
I count six wires into four terminals:
2x Pink/Green stripe
1x Black (may have white stripe)
2x Tan/Green stripe
1x White/Red stripe
There's still the mystery of why the gray STI piece is just hanging around with no sign of a wire. My gut tells me that the White/Red wire is the STI one and it was moved into the main body. Is there a reason why someone would modify the EEC test system this way?
Any other ideas on how to resolve this or to actually, ya know, pull codes?
Here's what's on the back of my EEC plug:
I count six wires into four terminals:
2x Pink/Green stripe
1x Black (may have white stripe)
2x Tan/Green stripe
1x White/Red stripe
There's still the mystery of why the gray STI piece is just hanging around with no sign of a wire. My gut tells me that the White/Red wire is the STI one and it was moved into the main body. Is there a reason why someone would modify the EEC test system this way?
Any other ideas on how to resolve this or to actually, ya know, pull codes?
Donkey shorts
I'm kind of scratching my head. I have to look at the diagrams a little more. At first glance, the wires at your diagnostic connector don't seem to match either '87 to '89, or '90 to '91.
In the air intake, between your air filter and your throttle body, do you have a Mass Air Flow sensor?
Your engine is a 1989 5.8 (351) right?
I'm wondering if somebody swapped for a roller cam/mass air engine. But I may also just be looking at the diagrams wrong.
If you look at Haynes' diagram for '87 to '89, and your wire description, it makes sense other than the white with the red stripe.
Two pink and light green.
One black (it probably has a white stripe).
Two tan with a green stripe (Haynes shows one, but wiring diagrams are abstract, so that's probably correct)
I'm wondering if someone put the white with the red stripe in the connector, maybe just to make it easier to jumper to the ground (Edit: Signal return, not ground), in order to trigger codes, using the paper clip method.
I'm going to say remove the white with the red stripe wire from the large diagnostic connector, reinstall it into the single self test connector, and try pulling codes.
If the single self test connector isn't functional, as far as holding the white with red stripe correctly, there is a way to read codes with a 12 volt test light.
Or, if your yellow "check engine" light lights up when you first turn the key to the run position, you can use the jumper (paper clip) method, and count the check engine light flashes.
Just did this and, whaddya know, it worked! I separated the white/red stripe wire from the main plug, plugged it into the STI plug and was able to pull codes. Hallelujah!
Next step is to fix them as I can. Or figure out which ones I can ignore.
Thanks to everyone who chimed in, especially Soup bean.
Last edited by matkinson13; May 9, 2024 at 06:35 PM.
Reason: Hit Submit too soon.
Glad you got it. It's hard to say what you'll find with a used truck.
My wiring harness O2 connector was plugged into the power ground connector, near the battery negative terminal.
That took me a while to figure out.
Glad you got it. It's hard to say what you'll find with a used truck.
My wiring harness O2 connector was plugged into the power ground connector, near the battery negative terminal.
That took me a while to figure out.
Our 84 diesel had a shop rag stuffed in the tranny filter, yes in the filter, not the pan.
Oh and the VRV was snatched off, and the vac hose plugged with a stick.
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