technical9

Car 1990 5.0 Mustang with 5 speed T5 tranny stock (no conversion, all factory). It's my friends car. He is getting code 67 which is the Neutral Safety Switch. Is there a way to bypassthis? We tried bypassing the clutch switch with no success. He also tried unplugging the Neutral Safety Switch and just jumping the wires, but the TPS didn't get anyvoltage when the switch was unplugged so he had to plug it back in.

What could be theproblem? Replacing the neutral safety switch is a big job and he doesn't have time for that if that is not the case or if he could just bypass it. TIA

Joel5.0

Did he run the KOEO with the transmission in neutral?........ if not, that is why code 67 is showing. He should also check if the code is present when a KOEO is run while keeping the clutch pedal pressed to the floor through the self test....... LUK

technical9

He did run the code reader in neutral with the engine on. Something weird is going on also when he has his clutch switch hooked up, the voltage at the TPS goes down drastically and doesn't run right, but with it unplugged it runs good, but there is a check get code 67 with the clutch switch jumped or not.

Joel5.0

There's a wiring snafu somewhere......the SIGRTN wire circuit is the only item shared between the clutch pedal switch and the other sensors (including the TPS)

technical9

What is the SIGRTN wire?

Joel5.0

SIGRTN is the sensors ground reference point......... a 3-wire sensor pinout is VREF - SIGNAL - SIGRTN.... a 2-wire sensor is SIGNAL - SIGRTN....

OR

BP sensor example =


ECT sensor example =

technical9

So we just looked at his car again and it was popping a fuse for the cluster, tps, etc. in the fuse box. I cornered the problem to these red and yellow wires coming from that fuse and cut those wires and rewired them to the cluster harness and now the fuse doesn't pop anymore, BUT we are still getting code 67 and now we get code 31 (I guess he said that code comes and goes).

Code 67 = Neutral Switch
Code 31 = EVP problem

Can I bypass the neutral switch on the tranny?
Why do you think it could be the SIGRTN wire? Is that a common ground?

Joel5.0

Reconnect clutch pedal switch, run KOEO and check if code 67 is present as a OD code...... if it is, rerun a KOEO self test while the clutch pedal is kept pressed to the floor through the KOEO self test..... LUK if code 67 is a show.

technical9

He just left so I can't do that right now, but hopefully tomorrow because he forgot to bring his clutch switch today (took it out of car).

I grounded the SIGRTN to the body and the check engine light goes away, but if we rev it over 3200rpm it comes back and goes away after the rpm's come down.

Checked for codes and he still gets the code 67. I will retest tomorrow with the clutch switch hooked up and with it depressed and not.

Thanks so far, feels like we are getting real close to solving this problem. And if it helps, he has a 25th anniversary 1990 5.0 Police Interceptor model (just incase some things are different).

technical9

We just ran the test again with the clutch switch hooked back up and depressed and still got code 67.