Electrical Car dosen't run without jumping the EEC IV test port

Mustang5L5 · Feb 19, 2024

Might be worth pulling the ECU out and checking pin 46 continuity to pin 40 and 60.

Fox2newedge · Feb 21, 2024

Ok... so this evening I put in my other A9L (which just recently came out of my '93 coupe that was running when I removed it). I disconnected the negative terminal and then I untwisted the Gray/Red and Tan wires (as they would have been in the EEC test plug). I installed the ECU and am getting the same results.

The fuel pump does not charge when I turn the key on. So, for giggles I replaced the EEC power relay and the relay by the MAF, still nothing. The two tan/green wires are still together as they would have been in the plug before it was cut off.

I know the fuel pump relay under the seat is good, as it works when I connect the gray/red and tan wires.

I also checked the injector harness ground and engine harness ground. They seem to have good continuity.

I am at a loss...

Mustang5L5 · Feb 21, 2024

You are going to have to trace out the Gray/Red and Tan wires and see where they go.

Tan wire does go to the pass side kick panel. Have you ever pulled that panel off and seen if there is any wiring hackery in there? I'll have to dig out the wiring diagram to ID the plug, but the tan wire would normally run across the firewall pinch weld harness and comes into the pass compartment in the passenger kick panel area. I believe two tan wires will be present on one side of the connector. One to the ECU and one to the dash. Might be worth seeing if this looks factory OEM. You can also test continuity to these wires to make sure they are intact and haven't been repurposed.

I believe the gray/red follows a similar path into the car but would need to check the wiring diagrams. You can test continuity to pin 46.

AeroCoupe · Feb 21, 2024

Just a fyi, the relay by the MAF is for the AC compressor.

Fox2newedge · Feb 21, 2024

I apologize Mustang5L5, I didn't see your post prior to me posting. I will check continuity on pin 40 and 60 to 46.

I had the ECU out tonight and didn't see anything out of sorts in the passenger kick panel area. As a matter of fact, I needed up pulling a factory retainer clip out of the tape where it had never been moved. It is pretty unmolested.

Mustang5L5 · Feb 21, 2024

If you are confident in the second ECU you installed, you likely won’t see an issue when you check for continuity between 46 and 40/60, but doesn’t hurt to check.

This one has me scratching my head. I’ll need to think some more on this.

Mcmahst · Feb 21, 2024

I think you might have to step back and start over. You need to determine what the Gry/Rd or Gry/Or, not sure the color, wire goes. I would pull the ECU plug and using continuity testing, figure out what pin it is, if any. Once you know that, then you can determine if the wiring harness is a stock harness. I say this because there is that wire on a 91-93 harness but not a 90. I mean, if it’s not a stock year harness, well there could be other issues. I could/might be wrong.

Fox2newedge · Feb 22, 2024

I did take a look at a friend's '90 GT and it has the same color wires at the EEC DLC. I truly believe this is the factory harness. It still has the blue Ford part number wrap on it as well.

I'm going to test the continuity on pin 40/60 as Mustang5L5 suggested and I'll try to determine which pin it is on the ECU. And... I may still send out the ECU just because I'm running out of options. I'll cross that bridge once I have some answers on the continuity.

Being both cars (mine & my friend's) have the gray/red, is it possible Ford just used gray/red wire instead of the black/white while transitioning to the '91-'93 style?

Not sure if it matters, but the car was manufactured in 01/90.

Mustang5L5 · Feb 22, 2024

It’s possible. Wouldn’t be the first time the EVTMs are wrong on a color. The 1993 manual does show that as being correct for pin 46 so it’s very likely.

Still, pin 46 is sensor ground, and you are putting 12v to it to make the car run. I must be missing something here but that doesn’t make sense

Mcmahst · Feb 22, 2024

It’s got to be frustrating.

Fox2newedge · Feb 26, 2024

Update...

I checked for the location of the gray/red wire on the ECU. It is pin 46. I even double checked the color at the ECU by pulling up the black harness cover at the ECU and confirmed the gray/red color is there at pin 46.

I then checked for continuity between pin 46 and pins 30 & 60. There is continuity between 46 and 30, but nothing between 46 and 60.

Unfortunately, I'm not sure what that tells me. Does that mean I have a bad engine harness?

Thanks again guys for everything!

Mustang5L5 · Feb 26, 2024

Was that with the ECU disconnected?

You said pin 30, but it was pin 40/60 and 46. Can you confirm you had the right pins?

Fox2newedge · Feb 26, 2024

The ECU was disconnected. And that is my bad... I tested 30/60 against 46. Was the ECU supposed to be connected?

Mcmahst · Feb 26, 2024

Mustang5L5 · Feb 26, 2024

No disconnected. Otherwise you’ll get false readings through the harness.

Mcmahst · Feb 27, 2024

Opps, sorry, misread. Yes, disconnected. Gotta stop drinking so much coffee.

Fox2newedge · Feb 27, 2024

Good morning all!

I went back last night and checked continuity between 46 and 40/60. There was no continuity between either of them. Regarding your question about testing at the correct pin, I used the attached diagram and counted them out (1-20 on the bottom, 21-40 middle row and 41-60 on the top row). Is that correct?

Also, I pulled up some other 1990 wiring diagrams to see where the black/white wire from pin 46 should be, so I could compare them on this car (if the gray/red is there instead of the black/white).

It seems that on this car Ford used the gray/red wire instead of the black/white wire. I found it at the ECU, the 8 pin connector going into the dash harness and the harness connection going to the O2 sensors...

Mustang5L5 · Feb 27, 2024

If there's no continity between any combo of pin 46 and 40/60, then it's likely that your pin 46 trace in the ECU is burned up. Time to open up the ECU and take a peek.

This video here right around the 8 min mark shows how to inspect the pin 46 trace. I also show around the 5 min mark how to check the continity of those 3 pins if you want to double check your work

Mcmahst · Feb 27, 2024

What would we do without you Mustang5L5? You are a true gentleman.

General karthief · Feb 27, 2024

Mcmahst said:
What would we do without you Mustang5L5? You are a true gentleman.

You'd have to depend on me and Noobz, in either case you're screw'd

Electrical Car dosen't run without jumping the EEC IV test port

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Electrical Car dosen't run without jumping the EEC IV test port

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