TCM computer unplugged

[Blipman]

I installed a GROM USB adapter today in the common spot behind the left seat, when doing this I noticed that there are 3 plugs to the TCM computer which were all unplugged. This is a JDM 1990 manual.

This is not wildly unsurprising in that my traction control has never worked and pushing the TCS switch does nothing... I shed no tears as early 90's traction control has always been pretty miserable in my experience.

I had originally assumed that it not working may be to do with my 1990 having a 2002+ ABS upgrade and thought maybe the wheel speed sensors/signals between these two systems weren't compatible. If it turns out to be these plugs then great, the car is apart at the moment so I can't plug them in and drive it. Before I do I'm concerned though that maybe these were unplugged for a reason and I'll do some damage plugging them in again.... there's the later model ABS and also a bit of a butchered wiring loom with cut wires in the front compartment. I just can't work out why someone might have unplugged these. Does anyone have any ideas?

 

[RYU]

Long story short... Many of us remove the TCS box entirely

 

[Superhatch]

My module went bad oddly after doing my timing belt (maybe power cycles?) and I unplugged it to get rid of the light and haven't plugged it back in since. I drove all last summer and this spring and the car feels great and on normal roads I've not felt like the back end was ever in danger of going out, even on 340 treadwear tires.

My guess is the TCM is bad, the light was on, and this was the easy solution.

 

[MotorMouth93]

If they did the 2000+ ABS upgrade then perhaps they used a cheap S2000 box which is not compatible with TCS instead of the very pricey NSX-specific part.

You should be able to tell what ABS module was used if you can see the part number. If you don't want TCS you can also remove the TCS computer and buy the bracket to hold the interior panel without a TCS computer (since the bracket attaches to the computer). The part number is 83724-SL0-J50.

 

[Old Guy]

The ABS wheel sensors are tied directly into the ABS control unit. The ABS control unit provides wheel speed signals to the TCS control unit. If the ABS unit you installed does not have the wheel speed signal pass through then the TCS will be non functional. Even if you have a 2000+ NSX ABS unit, the wheel speed signal may not be compatible the 1991 TCS unit. The 1991 TCS unit has part number 39900 SL0 023. Sometime after 1994 the TCS unit was revised to 39900 SL0 043 (probably with the DBW conversion) which appears to have stayed the same until the end of production. So, it could be that even if you have a wheel speed signal out of the ABS unit it might not be compatible with your early TCS control. Unfortunately, I don't how you would verify or refute the compatibility issue.

 

[MotorMouth93]

Even if you have a 2000+ NSX ABS unit, the wheel speed signal may not be compatible the 1991 TCS unit.

Why do you think the 2000+ NSX modulator is not compatible with the 1991 TCS? As far as I know, the whole reason to use an expensive NSX ABS modulator is because it will work with the old TCS, whereas the dirt cheap S2000 modulators with the same form factor will not.

 

[Old Guy]

Why do you think the 2000+ NSX modulator is not compatible with the 1991 TCS? As far as I know, the whole reason to use an expensive NSX ABS modulator is because it will work with the old TCS, whereas the dirt cheap S2000 modulators with the same form factor will not.

Perhaps I wasn't clear. The TCM received a revision during the production run. That revision may have only dealt with the 1995 drive by wire implementation and there may be no compatibility issue with later ABS units. I was just pointing out that the TCM did change and as such there was no guarantee that the 1991 TCM will be compatible with the 1995 and later ABS systems (the TCM appears to have remained the same from 1995 until the end of production). If you know that the later ABS units have been tested and are compatible with the 1991 - 1994 TCM then my comments are moot.

 

[MotorMouth93]

Perhaps I wasn't clear. The TCM received a revision during the production run. That revision may have only dealt with the 1995 drive by wire implementation and there may be no compatibility issue with later ABS units. I was just pointing out that the TCM did change and as such there was no guarantee that the 1991 TCM will be compatible with the 1995 and later ABS systems (the TCM appears to have remained the same from 1995 until the end of production). If you know that the later ABS units have been tested and are compatible with the 1991 - 1994 TCM then my comments are moot.

The modulators and ABS computers share the same part numbers from 1991-1996, so it's safe to assume that the communication protocol between the computer and the 91-94 TCS and the 95+ TCS remained the same. Also various vendors sell ABS retrofit kits and they claim to be compatible with 1991-1999 and keep TCS.

 

[Superhatch]

[MENTION=35392]Blipman[/MENTION] it looks like that part number is from an NA1 3.0L NSX from the web searching I could do this morning.

http://jp-carparts.com/honda/part_d...ype=NSX&cartype=19668&fig=B&fig1=1303&fig2=11

But the -023 part number is the only one listed on most US Acura sites.

From that link it's designated E-NA1...is that an JDM module maybe? When I search E-NA1 only Honda models are referenced.

 

[britlude]

late NSX ABS module is compatible with a 92 JDM TCS computer..... well it's working fine on mine

as others have said, the S2000 ABS only has TCS outputs for front axle (if at all) so isn't compatible, i investigated...

from post 19 on this thread.... http://www.nsxcb.co.uk/showthread.php?14147-collecting-parts-for-winter-project/page2


the TCS in the original post was probably disconnected as the owner at the time didn't like the way it deployed.

it's a bit too binary for some, if you don't understand the way it works.... when you do, you can come out of turns with the wheels spinning and it doesn't interfere