Hooking up check engine light after mass air conversion.

[strtrcr50]

I was on the phone with FRPP today with a question about whether I needed to repin the O2 harness After swapping in a automatic harness/a9p into an 88 stick car.(His answer was no). He then asked me if I had hooked up the check engiine light. I informed him no. He told me that without the check engine light, the keep alive memory would not work, and I have in fact noticed codes for just that. Anyone else who swapped an 89 harness into an 88 hook up the check engine light, and if so, how?

 

[strtrcr50]

From this diagram, it would appear that I would be checking at instrument connector a9 to make sure it I have a good circut, then backtracing the black with a light blue tracer to verify presence of the engine ind diode? And since there would be no reason for it to be there, what would I look for to add one. Also, it appears that the tan wire is only there on a 2.3, but that makes no sense. Also, looking at other diagrams, it shows the 5.0 also uses a tan wire on pin 17 to light the cel. Last off, while googling, people have posted that the dash wires do not have continuity to the eec harness. If that is the case, does anyone know where the wires are unhooked?

 

[strtrcr50]

anyone?

 

[93 LX]

So did you change the harness from the 88 to the 89? I am not sure why you just didnt repin the 88 but I think most of the online docs are centered around repinning not replacement....

 

[Boostedpimp]

You can stop by and repin my 88 if you want

 

[jrichker]

Copied from mustang88GT:

Adding a "Check Engine" light
Another difference between the speed density and MAF cars is that MAF cars have a "Check Engine" light in the dash to alert you to possible serious problems and it makes reading out self test codes much easier. The MAF cars have the "Check Engine" light located in the light panel on the lower right of the instrument cluster. Speed density cars don't have this window, but there is a "Check Engine" position for a light in the tachometer face, though there is no bulb installed. The wire from the EEC to the bulb (via the flex connector) is also missing.
In the '88 harness (not sure of other years), there is a tan and a black/blue wire connecting up to the 'Check Engine' circuit on the instrument cluster flex circuit. For MAF models, the tan wire hooks to the EEC STO/MIL line and the black/blue is for the lamp test out when you start the car. I don't know what these are connected to in an '88, but the test out feature does not work, and the STO/MIL line at the EEC-IV and self test connector is yellow/black. The wires connected to the check engine lamp probably end at some open connector somewhere, but I couldn't track it down, so I cut the tan and black/blue wires off the flex connector and ran a new wire to the STO/MIL wire on the self test connector under the hood (you could also tap in by the EEC-IV, but it was easier for me to go through the firewall. You can get a bulb socket from the HELP! rack at the local parts store, put in a N194 bulb, and voila, you now have a working check engine light.

 

[strtrcr50]

So did you change the harness from the 88 to the 89? I am not sure why you just didnt repin the 88 but I think most of the online docs are centered around repinning not replacement....

I used an 89 harness rather than repin the 88. I had one, and at the time I believed it was plug and play. Also, I didn't want to run new wires for the fuel pump circut and speed sensor. Even if I repinned, I still wouldn't have a functioning check engine light which as per FRPP tech line is required to make your k.a.m. s function. And I do get a code for the kams..

 

[strtrcr50]

Copied from mustang88GT:

Adding a "Check Engine" light
Another difference between the speed density and MAF cars is that MAF cars have a "Check Engine" light in the dash to alert you to possible serious problems and it makes reading out self test codes much easier. The MAF cars have the "Check Engine" light located in the light panel on the lower right of the instrument cluster. Speed density cars don't have this window, but there is a "Check Engine" position for a light in the tachometer face, though there is no bulb installed. The wire from the EEC to the bulb (via the flex connector) is also missing.
In the '88 harness (not sure of other years), there is a tan and a black/blue wire connecting up to the 'Check Engine' circuit on the instrument cluster flex circuit. For MAF models, the tan wire hooks to the EEC STO/MIL line and the black/blue is for the lamp test out when you start the car. I don't know what these are connected to in an '88, but the test out feature does not work, and the STO/MIL line at the EEC-IV and self test connector is yellow/black. The wires connected to the check engine lamp probably end at some open connector somewhere, but I couldn't track it down, so I cut the tan and black/blue wires off the flex connector and ran a new wire to the STO/MIL wire on the self test connector under the hood (you could also tap in by the EEC-IV, but it was easier for me to go through the firewall. You can get a bulb socket from the HELP! rack at the local parts store, put in a N194 bulb, and voila, you now have a working check engine light.

That's what I was planning on doing as a last reserve. I was hoping someone on here had found where the wire goes open so I wouldn't have to run an additional wire. I'm not inclined to pull my dash to track down the problem. In the diagram I shamelessly stole off your site, it shows the wire as being tan all the way into the eec(although that may be why it specifies 2.3) on 88-93. I guess I need to get the instrument cluster apart and start playing with a voltmeter.