New Main Harness M-12071-c302
 

I ordered my new Main Harness M-12071-C302 from Colorado Mustang Specialist. It says in the Ford Racing Performance Part book that It connects the Mass Air-Flow computer to the engine, sensors and relays, 26 page instruction book included with main harness. Contains very detailed instructions helpful hints and lots of illustrations for easy hook-up must be used with integral thick film ignition module distributor.

I asked the parts place and they said their was only one harness. There was no difference between the Automatic and a manual. When I did the AOD to T5 swap the harness was different if you used a manual computer with an AOD harness. Cutting the pin number 30 was how you solved the problem. I had Mustang Auto Tech do the work for me, because we bought a manual computer.

Why is there only one harness for sale by Ford Racing Performance Parts?

It may be only one part # but includes the cables for both. When I got the fuel injector harness it included two cables for what hooks up to the O2 sensors. One was for a manual, the other for an automatic. I couldn't really see any difference, though.

That's what I would think, too. I'm sure it covers it somewhere between page 14 and page 21. ;)

:)

Take care,
~Chris

thankx
 

Perfect. I will just see when the harness comes in. I didn't want to buy junk.

Received New Harness
 

I received my New Main Harness M-12071-C302 from Ford Racing Performance Parts. All the connections look like they match except #32 and 33#.

Connector #32 Fuel Pump Relay (FOAZ-14N O89-B) (FOAB-14B193-AB)

Connector #33 Wide Open Throttle A/C Cut Off Relay (FOAZ- 14N089-B) (FOAB-14B193-AB)

Both of these connectors are located on the driver side of the engine bay. Under the Mass Air Flow and the air flilter
What should I do?

I'm not sure I understand the problem. If the location is different, just relocate the relays to where the harness has them. Also, they should be mounted on the passenger side strut tower, not the driver side (unless you're British, lol).

We're racing today, but I'll check this thread when I get back tonight or tomorrow.

Take care,
~Chris

My reply
 

The new harnesses connectors #32 and #33 are different. They are the connectors to the Fuel Pump Relay and the WOT AC cut off relay. I guess I can rewire the new harness with the old connectors. I went and tested the new harness and ran all of the pins down and figured on what kind of ohms the harness has in it. Noticed the only part of the harness that has major resistance is Pin wire number four. I has 22 ohms like the diagram says.

I think I am going to send this harness back. I never installed it. Instead I'm going to go through my old harness. I am kind of disappointed that the new harness doesn't get me new wiring all the way to the injectors and all the sensors.

I reinstalled my old harness. I did an resistance test on the ECT sensors wires. I tested the green wire back to the Ten Pin connector and was 0 resistance. I tested the Black wire back to the ten pin connector and received 1 3/4 ohms. That seems like a lot of resistance. What do you think? I think my ECT is acting up?

I cleared the codes and reran a KOEO test.

I received the codes in this order.

63
63
1
22
35
51
54
63
22
35
51
54
63

63 TP sensor below minium voltage
22 MP Baro out of self test range
35 EVP/PFE circuit above maximum voltage
51 ECT sensor fault.
54 ACT sensor fault or open circuit

What do you think?

That is a lot of resistance. Have you tried tracing the wire for any obvious signs of resistance?

I will tommorrow.
 

I going to check out this black wire. What size of wire should I replace it with?

14 gauge would probably be fine, maybe 12.

What I found out!
 

Main Harness M-12071-c302 is a 1992 or 1993 5.0 HO harness. This is what Fords Racing Hotline told me. They said that It has many of the same connectors as my 1989 5.O EFI Harness. I can only see that connector 32 and 33 being different. I am sending this harness back because I just don't see paying 240 dollars for a harness that I have to work on. When buying the harness I asked if this harness would just plug into my 1989 5.0 and they said yes.

Instead I am just going to pull my current harness and go through that. I am going to pull it today and try to rewire that if there is to much resistance. It is much easier to work on the main harness and go through it while out of the car. I am also going to check out the injector harness. I looks like the injector harness can only be installed with the upper intake off. I think it is time to put a Explorer Intake in the car if I have to pull the original intake. I already have plans to replace that black wire coming from the ECT. Hope fully I can borrow the neighbors solder gun.