Hi, jaffaz32.
Before you touch the battery, please read the error code first.
You may loose one of the most important information in diagnosing the issue if you disconnect the battery or pull the fuse out before reading the code.
Then, please check the connection at the both battery posts especially the GND cable.
There is a GND wire from the EPS rack directly fixed to the battery GND cable terminal with a 10mm nut.
Poor battery connection or low battery voltage will trigger several warning lights such as EPS, ABS, etc.
Based on your other post regarding OBD1/OBD2 on this site, your NSX is likely to be UK spec 95 model.
If this is the case, you are very likely to have EPS controller ver. -023 (39980-SL0-023) and I’m afraid there is a known issue with this one and 100% guaranteed to trigger the EPS warning light sooner or later.
There are two power relays inside the controller and the relay capacity is not large enough under certain conditions that it will burn out the contacts resulting in EPS warning light.
Honda released TSB for Acura NSX with ver. -033 EPS controller for the similar reason and based on the information from other EPS owners, I know ver. -305 controller can also trigger the EPS light for the same reason.
For these controller versions, most of the time, the EPS error code will be #22 apart from the torque sensor failure at the EPS rack interface circuit.
There are other failure modes that will cause some of the FET to fail resulting in power assist in only one direction, etc.
For this specific failure mode, there will be no EPS warning light.
If your error code is #22, you will need to go through the procedure described in my blog at the NSXCB site.
http://www.nsxcb.co.uk/blog.php?1811&blogcategoryid=47
It will involve drilling extra holes on the board in order to install the high current capacity relays.
Some of the before/after photos...
All of the EPS controllers that I serviced with error code #22 showed burnt relay contacts resulting in poor relay operation.
If the EPS error code is related to the toque sensor or if you have rattle inside the rack, then I’m afraid you will need to service your EPS rack like others suggested.
It can be done in US or Japan.
So, first thing first, please read the error code and then check the status of your battery connection and the battery health.
Regards,
Kaz