Hi, chudson1549.
Please visit the following link on NSXCB site.
I helped another owner with ABS error code #51 as yours.
http://www.nsxcb.co.uk/showthread.php?9286-ABS-Upgrade-Support
Please note that some of the photos are RHD specific and although the pin position is the same, the connector orientation could be 180deg off on LHD model so please be careful. For example, the orientation of ALB motor relay socket described later is different between the RHD and LHD model because the pentagonal main relay box itself is mounted differently between the two models.
While there is a possibility that the cause of issue on your ABS is different from the above case or possibly the same but with additional cause, going through the above link should help you in understanding the system.
It’s quite long so please take some time.
You may already know but with the latest ABS modulator, you can’t erase the error code by disconnecting the battery or pulling the fuse, etc.
You must follow the specific sequences involving the brake pedal, SCS terminal
on the SoS upgrade loom (
not the blue 2pin connector at the passenger side on the factory loom) and the timing.
I don’t have experience with the SoS upgrade loom but based on several sources including the process in the above link, the pin#9 at the big black/orange connector that is connected to the latest ABS modulator is getting the power through the 2pin 250 WPC (the 2pin orange flat spade connector) on the original factory loom.
You can find the photo of this connector in the post #17 in the above link but here is the same one.
I believe you had to create your own connection from the SoS loom to this orange connector (possibly by removing the mating connector from the original classic ABS modulator).
This is the power for the ABS pump inside the latest ABS modulator and without +12V at the pin #9, you are 100% guaranteed to trigger error code #51 after starting the engine and when you start moving the car for the first time.
The 2pin orange 250 WPC has two thick wires (BLK and WHT/BLU).
BLK one is always at the chassis GND.
The WHT/BLU one will be at the battery +B voltage through 40A fuse (
no.30)
if the original classic ALB motor relay was activated.
The 40A fuse and the relay are both inside the
pentagonal shape main relay box under the bonnet.
For the other owner in the above link, the cause of code #51 was the faulty original motor relay.
Once he replaced it with a new one, his issue was solved.
You can find exactly the same relay at many locations on our NSX inside the fuse box, relay box, etc so as a quick check, you can just swap it with a known good one.
As in the post #19 of the above link, one of the switched terminals of the relay is connected to the battery through no.30 40A fuse.
You should always see +B battery voltage at this terminal even when the IG key is in Off position.
The other side of this switched terminal is connected to the WHT/BLU wire of the orange 2pin connector above which leads to the #9 pin at the latest ABS modulator.
Now to the coil terminals of the relay.
One of them will see 12V when the IG key is in P2 On position.
In order to activate the relay, the other side of the coil terminal has to be at the GND.
This is something you need to check as I don’t know how SoS loom is achieving this.
It is possible that it is connected to the GND via the two white connectors on SoS loom that will be installed inside the cabin behind the glove box or simply it was connected to the GND using a separate single wire with eyelet terminal.
As reported by nsx_2k as well as by other owners, I’m afraid using the soldering on pin terminal with heat shrink tube on top is not ideal against vibration.
My background is motor racing and we never use soldering for connector pin and always crimp it.
Therefore, it is possible that your relay is not activated due to lack of GND connection at the coiled terminal of the classic ALB motor relay.
Hope you will find the cause of the issue.
Kaz
