I've searched and searched and read every thread I can find on the subject, but I cannot for the life of me find the check connector on my truck to pull the CEL code. My truck is an 88 4cyl 5spd base model. The engine was replaced a few years ago and has very few miles since. The Chilton's book I have shows another box behind the fuse box -- no such thing. Other diagrams show another connector that I simply don't see. There's 3 round electrical connectors in that area, and there's one place on the harness between the engine and those big round connectors with 5 or 6 wires branching off, that appears to have been cut very close to the harness itself. Is that it? If so, what can I do? If someone's got the color codes for the two wires I need to short, that'd be enough I think if I can get them out of the harness.

Failing that, The CEL is off when the truck starts up, but as soon as I get the RPMs up a bit (on the high side of where i'd normally shift out of first) it comes on. If I keep the revs low it seems to stay off. What am I looking at?

One other question if anyone out there might have any ideas. When the truck starts the gas gauge stays buried at the bottom for a minute or two, then comes up. Minor annoyance, but I don't know what could cause this, and it makes me concerned about the rest of the electrical system. What could cause it?

Have you tried clearing your codes to see if it comes back.

The rpm should have nothing to do with the CEL

It should come on before cranking and go out when the engine starts .

If there is a problem it just stays on.

Sounds like electrical gremlins !!

For what it is worth the check connector should be attached to the fuse box it slides onto slot on the back of the fuse box.

The float in your tank could be sticking or getting dirty, it is an 88. if you drive your rpms up and cel comes on, it almost sounds like tps to me. Is your truck running like it should or is it running like hell? If it's not good, unplug the tps and it should improve, and if it does nothing, the tps is fouled.

Thanks guys. Thing runs great. The light comes on at key on, then goes off when it starts, then comes on again later (and of course it's the brightest light on the dash, almost distracting when driving at night.)

I saw the connector in the back of the fuse box. Good to know that's it! Going to check it on my lunch break today.

Okay, I checked, and the connector's definitely not there. i'm beginning to think the cut wires are the diagnostics. ARGH.

From the FSM:



That whole box/plastic piece is MIA on my truck. Anyone know which wires are the T and E1 by color code?

FSM is what everyone is gonna say... Factory Service Manual... EWD, electrical wiring diagram.

E1 is brown

T is Green /yellow stripe

Hope that helps

wyoming9 -- thanks! I was checking the FSM (the one available for download throughout the net) and didn't see color codes.

You can if you look on page 1460 of the 88 FSM pdf.

Or there's this from the 88 wiring diagram:

I have to ask since I don't see that you stated it (unless I missed it), is your engine EFI (22R-E) or with carburetor (22R)?

The carburetor models do not have a diagnostic port.