unable to pull codes - new FR harness

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ECM was supposed to be disconnected. So you did right.

This is blowing my mind. :bang:

ECM disconnected. Do these test on the ECM itself.

Use the volt meter set on ohms or continuity.

PINs 40 & 60 should have continuity
so should

40 and 46 should
46 and 60 should
 
mustang problem

I bet you bought a o2 harness for an automatic and fried the ecm. I had the same problem when I did a 4cyl to v8 swap. Finally figured it out on the third computer
 
ECM was supposed to be disconnected. So you did right.

This is blowing my mind. :bang:

ECM disconnected. Do these test on the ECM itself.

Use the volt meter set on ohms or continuity.

PINs 40 & 60 should have continuity
so should

40 and 46 should
46 and 60 should

Just checked, and they all have continuity. Used my crasftman DVM and ohms start at 1 with the prongs disconnected, and 0 when their touching. Readings were 0 for those 3 tests on the ECM.



I bet you bought a o2 harness for an automatic and fried the ecm. I had the same problem when I did a 4cyl to v8 swap. Finally figured it out on the third computer

Do you have a wiring diagram I can use to check if it's for an automatic or a manual trans? I specifically purchased one for the manual, so if they messed up I need to get in touch with them soon..
 
Do these readings indicate a bad ECM ?

Do you have the Case ground connected? The one below the EEC itself?

Just throwing stuff out there now.

If all your tests on the EEC and circuits are accurate. Then it kinda seems the EEC is at fault. There is nothing else I can think of, that wouldnt let the Self Tests start up.

But Id hate to see you replace the EEC, and that not be the problem.

Do you have anyone that you could borrow a EEC from and try?
 
Do you have the Case ground connected? The one below the EEC itself?

Just throwing stuff out there now.

If all your tests on the EEC and circuits are accurate. Then it kinda seems the EEC is at fault. There is nothing else I can think of, that wouldnt let the Self Tests start up.

But Id hate to see you replace the EEC, and that not be the problem.

Do you have anyone that you could borrow a EEC from and try?

Yeah, I have the case ground connected near the glove-box which is all metal in this car. I'd hate to replace it again and it not be the problem also, and unfortunetly I moved to a town where I hardly know anyone - none of whom have a mustang.

The check engine light I hooked up does not light up unless I disconnect the wire side that goes to the ECM and ground it out to the body, so I guess it has to be the computer fouled up.. unless there's any other tests to perform?
 
when I turn the key it does not come on. If i disconnect the side of the light that goes to the 'pink/lt green wire and touch it to the body it lights up. The other side is coming from my 'crank & run' power source. My ECM has been throwing a code 15 because of my quarterhorse...so it should light up always - unfortunately.

The book states: Pink/Light Green wire connect to check engine light. Connect other side of the light to a "Crank" and "Run" power source. This must be used.

I can only assume the Pink/Light Green wire is a ground coming from the computer and it closes the loop when there is an error code..?

If i have this wired correctly, then what do I test next to find out why the Pink/Light Green wire does close the loop?

Is the pink/light green wire the STO wire on your harness?
 
ECM is the only thing left it could be.

This an original V8 car?

66 mustang coupe w/302 EFI... it was originally an inline 6 but one of the previous owners threw in the '80 302 carb'd block.

Well, let me find/price a new ECM - hope that'll help clear up the 42/92 codes I was getting. (tho I was hoping the new harness would've taken care of that first lol)

I greatly appreciate all your time with this troubleshooting, I'll postback when I get the ECM to inform what it does. :nice: