Cel....trying To Check Codes. No Grey Plug?

First5.001 · Jul 12, 2016

My CEL has been on since I got the car. Cleared codes, came back. Last night I went to check them, but there's no grey connector. Just the big one and the brown one. Everything I read said not to use that one...after I already tried it. I'm not sure if someone cut the other one, or what. I've checked CELs on Ford's before so I know what it looks like. Any suggestions?

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Mustang5L5 · Jul 12, 2016

Brown one is hood light.

Follow the big one down to where it enters the harness. You may need to remove some tape or plastic retainer to expose the wiring. Do you find a broken wire down there somewhere?

What year is this car?

First5.001 · Jul 12, 2016

Didn't see any wires that were cut. I'll do more digging in the daylight after work. It's a 89.

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Mustang5L5 · Jul 12, 2016

Should be the same as my '88 then.

Pretty much coming from same spot

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jrichker · Jul 12, 2016

Do the simple stuff - unless you are color blind...

Check the wire color - the gray connector is connected to white/red wire - look for the wire...

Look for pin 48 on the computer wiring harness connector. This is where the white/red wire connects to the computer.

The following are diagrams courtesy of Tmoss & Stang&2birds

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

First5.001 · Jul 12, 2016

Thanks for the links. I suppose I'll start at the computer and work my way out

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First5.001 · Jul 13, 2016

Picked at the harness. This was the only red/white wire I could find in the harness.

Should I just put a pin in it and use it?

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jrichker · Jul 13, 2016

Use the ohmmeter function to make sure it goes back to pin 48 on the computer wiring harness. If it does, then jumper it to the black/white wire, turn the ignition to Run and the codes should dump.

First5.001 · Jul 14, 2016

Good thinking. I'll try that after work.

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First5.001 · Jul 14, 2016

No luck. Tried a the white wire with a red tracer, a red wire with a white tracer and nothing. Solid cel. Any other methods?

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Mustang5L5 · Jul 14, 2016

Is this harness original to the car as far as you know? Original 5.0 car?

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Mustang5L5 · Jul 14, 2016

First5.001 said:
No luck. Tried a the white wire with a red tracer, a red wire with a white tracer and nothing. Solid cel. Any other methods?

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The wire is more yellow/orange with a thin red tracer

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jrichker · Jul 14, 2016

Mustang5L5 said:
The wire is more yellow/orange with a thin red tracer

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Time. dirt and heat take their toll on wire colors in the engine compartment.

Find someone with a telephone line toner tool and connect the tone generator to pin 48 on the computer and then use the listener to trace the wire in the engine compartment.

See

View: https://www.youtube.com/watch?v=OyJsXpVZc5E
OR

View: https://www.youtube.com/watch?v=jP0AtN9hTP4

to learn how it works...

The first video uses a Harbor Freight http://www.harborfreight.com/cable-tracker-94181.html toner set - cost is ~$25.

There may be better quality or cheaper versions of this tool, but the best bet is to find a friend who has one of these tools and persuade him to help you.

First5.001 · Jul 15, 2016

As far as I'm aware it's stock to the car. The dirt and grease matches the rest of the engine bay. Again, pretty sure it's a factory 5.0/5 speed car. In the diagrams it's showing I can see a white wire with a red tracer. So that appears to be it, but there's no "dead end" where a plug would go. I have a power probe with the screw on wire piercing leads, I traced the white/red wire to the computer, but it doesn't appear to be in 48. I pierced it under the hood and linked it to the test lead in the plug. No luck.

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First5.001 · Jul 15, 2016

Here is where it goes into the ecm.

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jrichker · Jul 15, 2016

Go back and find pin 48 using the diagram for the wire side of the computer wiring plug and see what color the wire is. Then chase that wire out to the self test connector area and see if it is there.

First5.001 · Jul 15, 2016

Ok. I have to figure out what way the computer plug and diagram are oriented so I know where it is. Almost looks like that spot in blank on my ecm.

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First5.001 · Jul 20, 2016

I noticed even after having the battery disconnected for an hour the cel is still on the first start. Shouldn't it reset when the battery is disconnected?

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Mustang5L5 · Jul 20, 2016

First5.001 said:
I noticed even after having the battery disconnected for an hour the cel is still on the first start. Shouldn't it reset when the battery is disconnected?

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It should, unless the fault is a major fault that the eec sees pretty much immediately

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First5.001 · Jul 21, 2016

Gotcha. Really wish I could find the wire to check it. The only plug near it is the brown connector with the black/yellow wire. Did ford maybe use that one in 89? Anyway I can test the wire add not damage anything?

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