Code 67

Flatfoot · Dec 29, 2017

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

jrichker · Jan 1, 2018

This may not be what you need, but it is a start.

Code 67
Revised 18-Mar-2017 to include warning about the necessity of having a 5 speed O2 Sensor wiring harness when bypassing the wiring for test purposes

Cause of problem:
Clutch not depressed (5 speed) or car not in neutral (5 speed and auto) or not in park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code will prevent you from running the Key On Engine On tests.

External evidence from other sources claims that a code 67 can cause an idle surge condition. Do try to find and fix any issues with the switch and wiring if you get a code 67.

What the NSS (Neutral Safety Switch) does:
5 speed transmission: It has no connection with the starter, and the engine can be cranked without it being connected.
Auto transmission: It is the safety interlock that prevents the starter from cranking the engine with the transmission in gear.
What it does for both 5 speed and auto transmission cars:
The computer wants to make sure the A/C is off due to the added load on the engine for the engine running computer diagnostic tests. It also checks to see that the transmission is in Neutral (5 speed and auto transmission) and the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

The following is for 5 speed cars only. Do not do this unless you are sure that you have a 5 speed O2 Sensor harness!!!! Smoke, sparks and expensive pain in the wallet may ensue if you don’t.
The NSS code 67 can be bypassed for testing. You will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear. Jumper the safety pin to the ground near the computer.
Be sure to remove the jumper BEFORE attempting to drive the car!!!

For your next step, have a working DVM or multimeter with good batteries in it. Make sure that you really do know how to use it, because the rest of the troubleshooting depends on it.

Flatfoot · Jan 2, 2018

@jrichker @Mustang5L5 This is what ive done so far with no luck.

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.

Mustang5L5 · Jan 2, 2018

I've got a 1987 EVTM in the mail that should be here shortly. I'll take a peek and compare to my '88 EVTM that shows the wiring for the NGS through the o2 harness and compare to the '87 harness that lacks the o2 sensor loop and see if anything pops out at me.

As far as you know though, this is all original 1987 wiring correct? And now running an A9L with mass air swap?

Flatfoot · Jan 2, 2018

As far as you know though, this is all original 1987 wiring correct? And now running an A9L with mass air swap?[/QUOTE]

Correct

Mustang5L5 · Jan 6, 2018

Well, not a whole lot of differences between the 5-wire 87 and early 88s and the later mass air style wiring in terms of o2 harness jumpers. The early cars just didn't send the wire there. C350 is where pin 30 from that start/stop circuit comes into play which burns up the ECU, and you can see on the manual cars the early wiring didn't send pin 30 through there.

1987 (and I assume early 1988)

1988

One thing I did note though. This is the 2.3L engine wiring, but did have me wondering if this also applied to the 5.0 given that I don't see parallel wiring for the clutch and trans switch.

1987

1988

According to this, the 1987 2.3L only uses the trans switch rather than parallel with clutch switch as in 1988-later. Assuming early 88's received 1987 wiring, I wonder what would happen if you jumped out the body side trans NGS harness connnrvtor under the car?

Flatfoot · Jan 8, 2018

To see if mine is wired in parrallel do i just see if the clutch switch has the light blue/yellow tracer and black/white tracer going to it that the trans switch has? I'm also not getting voltage to the trans switch either. I unplugged the trans switch and checked the harness connector for voltage.

Mustang5L5 · Jan 8, 2018

Yup, wire colors should be the same.

If you pull the driver's side kick panel, there's an 8-pin square plug located there that is the trans harness coming from under the car. You should see the wire colors there, and jumping them out there is much easier than going under the car.

Let me recheck wiring diagrams tonight and come up with something to test.

Flatfoot · Jan 8, 2018

Ok. Thank you!! You are a huge help

Mustang5L5 · Jan 8, 2018

Read this thread a bit. The issue is pin 30 and 46. I think some if this might be key in solving your issue

https://www.stangnet.com/mustang-forums/threads/efi-wiring-help-on-86-5-0-pin-30-46.832635/

Flatfoot · Jan 8, 2018

Switch is wired in parrallel

Flatfoot · Jan 9, 2018

Well I fixed it. Hope this may help others out there with this problem. Huge help from @Mustang5L5. He pointed me in the right direction. I have a 88 speed density car built in 10/87 and has been converted to Mass Air. It came with the early O2 wiring harness (5 wire) with no loop (apparently changed them later in 88). Read here for more explaination.

http://forums.corral.net/forums/gen...ar-differences-3.html#/topics/1094179?page=32

After googling everything I could about pin 30 and pin 46 and reading every thread it hit me after reading the very last post on this thread.

http://forums.corral.net/forums/eec...problems-computer.html#/topics/1133346?page=3

I came home and looked and the O2 harness connector on ECU side is 8 wire. I needed the loop to jump the wires for the purple/ yellow wire and light blue/yellow wire. Ran the codes no more code 67.

Mustang5L5 · Jan 9, 2018

That's just strange that you had a 5-wire o2 harness with no jumper, and a 8-wire engine harness. Usually the car's I've encountered have had 5-wire on both sides, so I didn't even think to ask to look there. Glad you got it fixed, but I wonder if a jumper was ever there or that harness was swapped out at some point.

But always a great feeling when you solve something. Thanks for the update and more info to help people out in future searches

Flatfoot · Jan 9, 2018

No jumper on original. Didn’t even have holes in the back of the plug for it. My original got burned on the headers some and ordered a replacement.

Blown88GT · Jan 10, 2018

Flatfoot said:
Well I fixed it. Hope this may help others out there with this problem. Huge help from @Mustang5L5. He pointed me in the right direction. I have a 88 speed density car built in 10/87 and has been converted to Mass Air. It came with the early O2 wiring harness (5 wire) with no loop (apparently changed them later in 88). ..

I came home and looked and the O2 harness connector on ECU side is 8 wire. I needed the loop to jump the wires for the purple/ yellow wire and light blue/yellow wire. Ran the codes no more code 67.

I have an '88 SD built in 12/87 & converted it to Mass Air a long time ago. I never got a code 67 & never even looked at the O2 wiring harness. With the Megasquirt, the O2's are still there will all the wiring intact. They are available to the MS but only the WB-O2 is looked at.

I did 2 different mass-air conversions, 1st with the Ford conversion kit & later with an A9L The A9L did require this:

In 1986-87(EFI) vehicles with thermactor pump and plumbing still attached, the
movement of the two pins on the EEC IV connector is required:
Pin 51 must be moved to Pin 38 in EEC IV connector.
Pin 11 must be moved to pin 32 in EEC IV connector.

In 1986-87 vehicles, you may need to connect other wires to avoid EEC error codes. These are:
1. Pin 19 is the fuel pump monitor. A wire with a pin is provided to put in pin 19, and it
must run to the hot wire on the fuel pump (Pink wire with Black tracer under driver
seat). This wire is only necessary if you do not want a diagnostic code. Omitting this
wire will not help performance.
2. Pins 3 and 6 are vehicle speed sensor lines, and will affect some closed throttle
operation of your car.
A. Pin 6 is the Orange ground wire and should be spliced/soldered to the Orange
with Yellow tracer ground side of the speed sensor. The sensor is found at the
end of the speedometer cable, near tail of transmission.
B. Pin 3 is the Green + wire and should be spliced/soldered to the second wire, Dark
Green with White tracer.

Flatfoot · Jan 11, 2018

Did some more digging last night. There are no splices in the the ecu harness so i assume that the previous owner used an 89 or later harness to do the mass air conversion and connected it to the speed density O2 harness. The speed sensor O2 harness only had 5 wires and did not have the loop in it and no place for the loop to be installed. I ended up replacing the harness and installed the loop. Immediately noticed the idle not surging like it did before and no more code 67. The speed density O2 harness was my problem.

Mustang5L5 · Jan 11, 2018

Flatfoot said:
Did some more digging last night. There are no splices in the the ecu harness so i assume that the previous owner used an 89 or later harness to do the mass air conversion and connected it to the speed density O2 harness. The speed sensor O2 harness only had 5 wires and did not have the loop in it and no place for the loop to be installed. I ended up replacing the harness and installed the loop. Immediately noticed the idle not surging like it did before and no more code 67. The speed density O2 harness was my problem.

That actually makes sense because the earlier harness routed the wires differently if you look at my 1987 vs 1988 wiring diagrams up above. They route through different connectors so the engine harness routing is different. So if the OP swapped in the 1989 harness, then that harness requires the o2 loop.

If you had had the original 1987 or very early 1988 harness with the 5-wire O2 harness and 5-wire harness on the body side, you would have never had an issue because the wiring would have already been present

whitey92lx · Oct 11, 2018

@jrichker I am reading this thread and wondering if I may be battling the same issue. I will re-check everything again since I thought I did all of this back in 2016 when I originally owned the car.

edit: Just re-read through my previous build thread and I did check this already. I had to repair my burnt our signal return wire on the ECU from someone else who fried it before I owned the car. But I did verify my O2 harness does have the correct O2 harness for the Mass Air conversion

Dan02gt · Oct 12, 2018

I fount this issue for days on my car and came to the conclusion that the blue/yellow wire for pin 30 was damaged somewhere in the harness and barely making a connection. My fix was to run a new wire from pin 30 right off the connector at the ECU to the blue/yellow wire in the center console that is there for the auto trans shifter as that plug is unused on a manual car.

Code 67

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