ABS trouble-shooting (SOS '01+)?

[R13]

Another Update

I gave my multimeter a workout last weekend. At the time (remembering this has been a sporadic issue) I did the tests:

- I got continuity between the RR speed sensor plug, and the connector at the other end of the trunk harness (grey connector that plugs to the body harness).

-I also got continuity between the RR speed sensor plug and the ALB harness connectors under the dash (with the trunk harness plugged back into the body harness obviously)

-I also looked at the SOS harness connectors. Although I haven't tested them, or taken anything apart, they look basically like they did when I installed them. I had everything well secured with wire ties under the dash in such a way as to minimize any stress on the connections. Here's a picture of the SOS connector (taken ~10 minutes ago) with the two RR speed sensor leads highlighted with dots:

My next steps I think will be:

1) re-connect the multimeter to just the trunk harness and then moderately wiggle it a few places to see if I can get a break in continuity.

2) Find the pin-out for the SOS harness and verify continuity from the connector pictured above to the main connector on the ABS unit in the frunk.

 

[Hagasan]

I already know the wiring schedule as I made up my own harness. I'm not willing to divulge how/what I made (just like SOS wouldn't when I questioned them) as I had to work it out...... but if you haven't worked it out in a few days PM me and I can tell you relevant pin-outs.

I don't have the info to hand right now anyway but I would be checking under those rubber Hellerman sleeves on the white plugs. My hunch would be those.....

Another Update

I gave my multimeter a workout last weekend. At the time (remembering this has been a sporadic issue) I did the tests:

- I got continuity between the RR speed sensor plug, and the connector at the other end of the trunk harness (grey connector that plugs to the body harness).

-I also got continuity between the RR speed sensor plug and the ALB harness connectors under the dash (with the trunk harness plugged back into the body harness obviously)

-I also looked at the SOS harness connectors. Although I haven't tested them, or taken anything apart, they look basically like they did when I installed them. I had everything well secured with wire ties under the dash in such a way as to minimize any stress on the connections. Here's a picture of the SOS connector (taken ~10 minutes ago) with the two RR speed sensor leads highlighted with dots:

My next steps I think will be:

1) re-connect the multimeter to just the trunk harness and then moderately wiggle it a few places to see if I can get a break in continuity.

2) Find the pin-out for the SOS harness and verify continuity from the connector pictured above to the main connector on the ABS unit in the frunk.

 

[R13]

Working under the dash can be tricky, but I should be able to slit them enough to inspect the connection. I'm curious how the connections were made; solder or some type of spade connector.

I think I have all the pin info I need. I know which wires on the SOS connector go to that speed sensor based on knowing the matching wires on the body harness side. I found the pin out of the ABS computer connector on NSXCB (so I must again thank etang789).

 

[Hagasan]

I think you'll find it was Kaz that posted that pinout info, not etang... but it is all in the shop manual.

So anyway if you get stuck then I've fully drawn down the complete pin out schedule from both white plugs & relay to the ABS plug.

I think the SOS harness is soldered. I made mine with the correct factory style "tyco" connectors so the cable ends are enclosed....
Good luck in the mean time...

Working under the dash can be tricky, but I should be able to slit them enough to inspect the connection. I'm curious how the connections were made; solder or some type of spade connector.

I think I have all the pin info I need. I know which wires on the SOS connector go to that speed sensor based on knowing the matching wires on the body harness side. I found the pin out of the ABS computer connector on NSXCB (so I must again thank etang789).

 

[nsx_2k]

I agree with Hagasan. I *think* your problem maybe under one of those heat shrink tubing. The wires are soldered to the connector (end to end soldering). I would *gently* pull on the wires to see if the wire comes loose or pops out. The shrink tubing itself will hold the wire in place, thus appearing to be connected; however, the connection is not solid. Consequently, when the car encounters vibrations or heat, the connection fails and you get the error you reported.

 

[R13]

I agree with Hagasan. I *think* your problem maybe under one of those heat shrink tubing. The wires are soldered to the connector (end to end soldering). I would *gently* pull on the wires to see if the wire comes loose or pops out. The shrink tubing itself will hold the wire in place, thus appearing to be connected; however, the connection is not solid. Consequently, when the car encounters vibrations or heat, the connection fails and you get the error you reported.

I plan to inspect later today. It does seem a little strange for that to be a failure point. That location isn't really subject to much vibration (relatively anyway) although it is right next to the heat/AC ducting, so the thermal aspect could be something.

I'm still going to be checking the trunk harness as well. It's a little too coincidental for just that corner to be having a problem when it's the only sensor on that harness.

 

[R13]

So.

I tugged on the SOS harness wires, and got nothing. Wanting to put that possibility to bed, I then grabbed a hobby knife and carefully slit the rubber shrink tubes for the two wires in question.

The solder joints on both appear completely intact, I gave each wire a little wiggle while free of the tubing and there was no indication of a failure.

With that, I think I'm back to the trunk harness as being suspect, even though it passed a cursory continuity test unless there are any other ideas.

 

[R13]

Can someone confirm that 32108-SL0-A42 is the correct part number for the trunk harness on a '92? The first year that the harness is listed in the online parts reference is '93, and that part# carries through to '05. I can't imagine they changed anything, but want to be sure.

thanks.

 

[warrenw]

Subscribed to this thread...

Seeing I have this ABS upgrade on a '91, there is a lot of valuable learning going on here.

Sorry, I can't help more. I feel your pain. Look at it this way, at least it fails solid, when you find it, you will know. I hate the intermittent problems that just come and go...

You may want to revisit the wheel sensors. There maybe a bad connection, cable, or bad new replaced sensor. The problem only showed up after your axle work.

good luck

 

[R13]

Dropping information:

'91-'92 Trunk Harness: 32108-SL0-A30

'93+ Trunk Harness: 32108-SL0-A42

No idea what the actual differences might be.

 

[Hagasan]

Dropping information:

'91-'92 Trunk Harness: 32108-SL0-A30

'93+ Trunk Harness: 32108-SL0-A42

No idea what the actual differences might be.

I'm getting the feeling your clutching at straws a little? Why don't you just isolate every section on the harness you have at each connector and then check all sections including the SoS harness for continuity with a meter. It seems a bit random what you're thinking? Just thoroughly checked each section in it's entirety, not just two wires. You may be missing a fault. Visually checking the SoS harness will not check for dry joints in the solder etc....

 

[R13]

Edit:

Ok. Grant it I've still just looked at the RRW+ and RRW- circuit so far, but.

WSS -> Trunk harness -> Body harness connector: Continuity = yes

Body harness connector in trunk -> Body harness connector under dash: continuity = yes

SOS connector under dash -> Terminal connector @ ALB Unit: Continuity = yes

So, I'd wager if I cleared the code and started the car right now, I would probably not duplicate the fault. I may try that tomorrow.

The Code it saved was an OPEN or SHORT in that WSS circuit, so unless it's throwing a false code, when things go wrong, one of the above paths should fail the continuity test.

 

[R13]

Update to above.

As I suspected, after failing to find an open or short in any section of the harness, I cleared the code and drove the car for a half hour with no ALB fault codes thrown.

HOWEVER, after I reconnected everything, the electric trunk release no longer worked, and halfway through my drive, the right-hand blinker started acting like a bulb was out (blinking 2x as quickly as normal).

After stopping for a while (~4 hours), and then re-starting the car for the return trip, the blinker now worked correctly again, but the trunk release was still out, and after driving over some slightly washboarded pavement, I also got the ALB fault again. After stopping again for a few hours to eat dinner, there were no faults after restarting the car again.

In summary: In my opinion this reinforces my suspicion of the trunk harness. I've already got a couple of possible lines for a replacement, so I'm going to go that route and then dissect the old one to see what was up.

 

[R13]

Resolution:

The problem was:

1) The gap between the pickup on the wheel-speed sensor and the teeth on the trigger wheel was too large. This was exacerbated when the car was driven hard because the thermal expansion of the hub & knuckle would increase the gap further.

BECAUSE

2) There were pockets of corrosion on the knuckle where the wheel speed sensor attaches, preventing the flange on the sensor from sitting flush against the mating surface.

AND

3) Bolts that were a) too short and b) of the wrong thread pitch had been used to attach the sensor (I had un-knowingly re-used these bolts when I replaced the sensor because that's what was there). This meant it wasn't possible to snug down the bolts without stripping threads.

Longer bolts of the correct thread pitch allowed proper tightening on a now-clean mating surface. After this I've completed a few thousand road miles as well as a track weekend with no re-occurrence.


Take-Aways from this experience:

-"Open or Short" ABS codes (2001+ system) can also mean just a bad signal from the WSS, and doesn't necessarily indicate a literal open or short.

-The WSS-to-trigger wheel gap tolerance is VERY tight, and sensitive to change. I'd recommend cleaning the mating surface any time a WSS is replaced.

-If you happen to lose the mounting bolts, they are apparently M8x1.25. M8x1.5 will act like it fits, but is too course.

 

[whrdnsx]

The speed sensor bolts are not M8 x 1.0. The correct bolt is M8 x 1.25 & is used through out the car. I'm 99.9% sure that M8 x 1.0 is not used anywhere on a NSX. I'd say that you may have used a 5/16 UNC bolt which is too corse.

 

[R13]

The speed sensor bolts are not M8 x 1.0. The correct bolt is M8 x 1.25 & is used through out the car. I'm 99.9% sure that M8 x 1.0 is not used anywhere on a NSX. I'd say that you may have used a 5/16 UNC bolt which is too corse.

Confirmed in manual, post edited accordingly. Must have been M8x1.5 that was in there. I need a tap/die set so I can at least measure that kind of thing at home.

 

[stuntman]

Re: Resolution:

The problem was:

1) The gap between the pickup on the wheel-speed sensor and the teeth on the trigger wheel was too large. This was exacerbated when the car was driven hard because the thermal expansion of the hub & knuckle would increase the gap further.

BECAUSE

2) There were pockets of corrosion on the knuckle where the wheel speed sensor attaches, preventing the flange on the sensor from sitting flush against the mating surface.

AND

3) Bolts that were a) too short and b) of the wrong thread pitch had been used to attach the sensor (I had un-knowingly re-used these bolts when I replaced the sensor because that's what was there). This meant it wasn't possible to snug down the bolts without stripping threads.

Longer bolts of the correct thread pitch allowed proper tightening on a now-clean mating surface. After this I've completed a few thousand road miles as well as a track weekend with no re-occurrence.


Take-Aways from this experience:

-"Open or Short" ABS codes (2001+ system) can also mean just a bad signal from the WSS, and doesn't necessarily indicate a literal open or short.

-The WSS-to-trigger wheel gap tolerance is VERY tight, and sensitive to change. I'd recommend cleaning the mating surface any time a WSS is replaced.

-If you happen to lose the mounting bolts, they are apparently M8x1.25. M8x1.5 will act like it fits, but is too course.

Good to know!