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Discussion Starter #1
1988 Mustang factory V8, 5 speed car. Mass Air conversion done with A9L computer. When KOEO is done I get code 67 along with some EGR codes too. Trying to fix the 67 code. When codes were pulled a/c was off, car in neutral and clutch pushed in. A Tr 3550 tranny is in the car and the sensor is plugged into the tail and connected. Have also tried unplugging the switch on the clutch pedal and jumping the connector and still get the code. The car has a build date of 10/87 and has the speed density O2 harness (5 wire harness, no loop). Any help is appreciated! Thanks
 

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I could email you the troubleshooting from the workshop manual if it'll help. Just let me know
 

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the clutch pedal has nothing to do with that circuit

the neutral sense switch on the stock trans must be closed

pin 30 must see a volt drop within the eec
 

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Discussion Starter #4
This is what ive done so far

Key on, engine off and measured voltage at the 30 Pin. Came out to be less than 1 volt. So it shouldn't be the Neutral Drive circuit but checked the sensor anyway.

Disconnected the sensor in the tranny and measured the resistance. Resistance was less than 5 ohms

Key on, engine off and measured voltage at the 10 pin. Voltage was greater than 1 volt. So it says short to power in a/c clutch circuit

Electrical is not my thing and this is all new to me. Any guidance here would be greatly appreciated.
 

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yep

your description of test is not detailed enough

you must tell, if you are testing complete circuits,,,,,by back probing or did you disconnect something

where is this 1 volt = short to power?

shall we start from the beginning?

if you look at a wiring diagram,

Can you tell how the circuit works, by id'ing the power, ground and load?
 

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YOU HAVE A 5 SPEED CAR

And are using a test for a neutral drive switch that is on a AUTOMATIC TRANS

So which is it?

You really want to use tests that pertain to your application, no?
 

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Discussion Starter #8
Obviously very new to this. Yes it is a manual transmission. Let me know what I need to do. If you could dumb it way down for me too so I can follow you. Thank you for your time in advance Indy. I appreciate it
 

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does your transmission have the neutral sense switch that's on the front of the top cover?
 

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is the switch open or closed in neutral?
 

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Discussion Starter #12
I’m out of town till Sunday and will check when I get back. Do I check it by unplugging the switch from the harness and measure the resistance in neutral to make sure the switch is open and then put it in gear and measure again to see if the ball on the back of the switch closes the switch? Or is that wrong?
 

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yes, look for continuity

need to know the state, in neutral

open or closed
 

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that is good

you must have a wiring problem

is this switch in parallel with with the clutch sense switch?

pin 30 is looking for low voltage, if it sees hi then it assumes both switches are open

therefore if you do not have clutch sense switch installed, the voltage will always be hi

and hence the code
 

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Discussion Starter #16
I'll check to see if it is wired in parallel tonight. I did check the voltage to the trans switch at the connector and there isn't any voltage there. I think i definitely have a wiring issue going on.
 

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would you like me to scan and email you a pic of the wiring diagram?

might be easier to see, that pin 30 is monitored inside the ecm
 

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Pin 30 wiring, upper left corner.
 

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Discussion Starter #20
I fixed it. Hit me today after doing a bunch more reading. I had to add the loop in the O2 harness. My harness is 8 wire on the ECU connector side and 5 wire on the O2 side. Speed density cars didn’t have the loop. You need it when you change over to mass air on the 87 and early 88 cars I guess. Thank you for your help. Ran the codes and no code 67
 
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