Neutral Safety Switch And Cruise Control

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by John Dirks Jr, Oct 12, 2017.

  1. Among the myriad of things to fix on my 93 Convertible project are the neutral safety switch and the cruise control. The car was originally a T5 car but now has AOD. The ecu is A9P which is correct for the AOD. The trans is rebuilt and has a new NSS switch in it. The harness is plugged in down at the transmission.

    I believe my problem is under the dash near the pedals. The clutch pedal had been removed along with the switch that would normally be associated with it. The harness plug for ignition interrupt that would have been connected to the clutch NSS switch is jumped with a wire between the contacts in the plug. That same clutch mounted NSS switch would also have had the interrupt circuit for the cruise control connected to it. That cruise control interrupt harness is hanging up there simply not connected, nor jumpered.

    So, where to I begin? I need to somehow bypass the safety features that would be associated with the clutch pedal but allow the circuits to function as they would in an AOD application.

    Currently, the car will start in any any gear. It should only start in park and neutral. Also, cruise wont engage and I think that also may be related to the disconnected harness where the clutch used to be. It doesnt need that circuit anymore since there is no clutch. It only needs to deactivate cruise when the brake is pushed.
  2. Under the dash on the AOD's, the NGS plug (the clear one) simply hangs free and is not connected. There is no NGS that runs to the AOD, the two wires simple are not connected to anything in the harness, so on a T5-to-AOD swap, that plug will hang free.

    The starter plug (grey plug) has a OEM jumper wire that jumps it out. A 30A fuse or so installed and taped up should do the same thing. (the fuse shouldn't ever blow, but if the car never starts, check this)

    The o2 sensor harness jumper wire should be checked to ensure it is pinned correctly.

    Under the car, the AOD's harness should connect to your existing harness once you remove the small 1-foot long t5 harness. This is the NSS that will prevent the car from starting in any gear other than N or P.
    DSB88GT and 90sickfox like this.
  3. Thanks for the info.

    Is it possible for the T5 harness to plug into the AOD NSS at the transmission? I’m asking this because maybe I don’t have the correct harness part under there. I wouldn’t have been paying attention when previously installing the trans. I just plugged in what was there and it physically snapped in apparently normally.
  4. No. The t-5 harness has a jumper and a different connection.
  5. New info to share and questions. Refresh, Car is originally T5 and had been swapped to AOD by previous owner. It has A9P ecu and the correct NSS harness on the trans I think, or it at least correctly plugs in to the NSS on the trans easily. I'm trying restore NSS and cruise control.

    Q) How do I check to make sure the o2 harness jumper wire is pinned correctly?

    I discovered the factory wire (red with blue stripe) that should be running from ignition switch to the starter solenoid had been cut where it comes out of the harness near the coil. A patch wire is running from the solenoid to the ignition switch on the column. This patch wire is obviously bypassing the intended ignition start circuit and allows the car to start in any gear.

    Under the dash, the factory ignition switch interupt circuit at the black plug (would have been clutch switch on the T5 platform) is jumped with the factory jumper connector. Still irrelevant since all of this had been bypassed with the patch wire as described above. So, I figured I'd try and re-connect the factory ignition start circuit and see what happens.

    Before reconnecting it I decided to check with a voltmeter to see whats happening on the circuit when I operate the ignition switch. What I discovered is the factory start circuit wire (red with blue stripe) near the solenoid shows 2.66v in the ignition "run" (not start) position. When the the key is turned fully to the start position, the voltage drops slightly to about 2.62v. This is wrong obviously since this wire should only show voltage when the key is turned fully to the start position, and it should not show any voltage in the "run" position as it currently does. Furthermore, this 2.66v that shows up on the key "run" position is only present when the trans shifter is in Park or Neutral. Interesting huh? This seems to indicate the NSS system is at least partially correct. I described above that a factory jumper connector was found in the black plug that would have been to the clutch switch on the T5 setup. I can pull this jumper and the 2.66v presence described above goes away.

    I'm guessing that maybe there's a slight short circuit somewhere in the wiring between the ignition and start circuits. Maybe the previous owner decided to bypass it all instead of tracking the problem down. I also understand that something could be wrong with the swap process from T5 to AOD. Something like a connector pinned wrong.

    All in all the car is still fully functional with the factory start circuits bypassed by the patch wire I described. But in the end, my NSS and cruise are non functional and I think their malfunction is related. I'd like to restore them.

    So what the heck is going on here? I can do more diagnostics if anyone has a request.
  6. Reference voltage for the o2 sensor would be about 2.?? Volts. I suspect an issue at that o2 sensor harness that runs from the k member over to behind the air box. Some people run it through the passenger shock tower and down by where the factory fuel lines are when they do a wire tuck.

    That harness needs to be checked or it can damage the computer internal components. If the NSS circuit isn't complete running through that harness the car won't start by key. That harness, if pinned incorrect, can cause o2 sensor voltage to be seen at the red / blue wire.
  7. Okay. So now I definitely need to check the pin positions at the o2 harness. When I’m looking at it, what should I be looking for? If pins are in the wrong position, is it simply a matter of moving the pins to different positions in the harness connectors?
  8. This car appears to have the correct o2 harness correctly pinned for the AOD. Can someone please confirm?

    2754E97B-0931-4413-BE71-88DD27645AC2.png 81BE4DD4-A785-429D-9B80-71254E05ED72.png
  9. Still tracing. Got the correct nss harnes at the trans. Here it is removed. Tested all 4 wires and no shorts in that part at least.

    I checked continuity between the solenoid and clutch connector where the jumper goes in AOD application. Good continuity and no shorts to ground on that part.

    Over at the ECU I found this bare ground wire disconnected from its intended place at the eye. I verified by looking at my 92 Hatch. On that car the ground is connected to the same eye as that insulated ground. What issues could this disconnected ground cause. Gonna re-connect it anyway.
    D2ED7D56-51BF-4C82-A34E-32093E8C9A08.jpeg 3FAB0B79-3397-46AF-98D5-89A05410D821.jpeg
  10. Ahhh, there we go

  11. Maybe it’s got something to do with the previous hack job alarm system with remote start, ignition kill and all that. Cutting it all out now. Carefully mind you. Although it will be amazing if this thing starts and doesn’t burn when I’m done with my own hackery

  12. Getting more confidence in the idea that it’s the previously installed alarm system messing things up. Man! Every switch on this dang car is boobie trapped!! Even the damn trunk release!! I’m cutting it all out.

    In these pics you see the important stuff I’m tracking down. The cut ignition wire hanging from the column. The other end of such sticking out of the harness. At the column you see the hacked insulation where alarm functions were tapped in. Finally, over near the ECU where the red / light blue ignition circuit was split.

    43EABD5B-EAD9-4476-9F42-22A645CCDB4C.jpeg FBC78753-488D-42E1-BDF7-1C86A6AEDCE9.png C518E1A8-45CF-4A6F-88D3-8D601BE56A8D.png
  13. That was it! After removal of the alarm system wiring and repair of harness taps, the neutral safety switch works perfectly. Still seeing 2.6v at the ign wire near the solenoid in the run position but only when the wire is unhooked from the solenoid. When connected the voltage disappeares. I’m curious about this but it doesn’t seem to be causing problems.

    EEC IV is talking to me normally. It’s logged 54, 82 and 85.

    82 and 85 don’t concern me as they are Evap canister and smog pump solenoid which are not present.

    54 is Air intake temp circuit open. That I’m interested in and will be moving to resolve.

    722DCD70-0070-44CC-8B7B-841601B283D7.jpeg 674A2DDF-45B5-4EEF-BE0C-083E7584CB00.jpeg 3B5E8FE6-2ED0-485C-B0D0-E30FA1D0C10E.jpeg

    Attached Files:

    karthief likes this.
  14.'ve got a hell of a lot done. All I've managed to do after work is go to tractor supply and buy some crap to use as hold downs on my car trailer.

    Not sure what that voltage is on that circuit.

    Glad to see the PO at least did the swap right.

    Have you checked the ignition switch ? I've run unto several that were melted at the pins. Eben had a couple that fell apart when I touched them. :nonono:

    Glad you're saving that car from all the crap the PO did.
  15. Yeah, I thought about the possibility of the ignition switch leaking voltage from the run to the start circuit.

    Of the multiple previous owners, not all of them were horrible. Of all the butchery on this car, most of it I've been able to sort out using what's there winding up actually correct.
    90sickfox likes this.
  16. In the past I'm guilty of hacking up some pretty nice cars. Back then ( 20yrs ago ) you could buy these cars for under a grand in good condition.

    I'd cringe watching someone dig through my old wiring debacles. Now, I try to keep everything as close to factory wiring as possible.