EPS Light came on

[idk706]

Hello to my favorite forum.
My JDM 1991 A/T RHD EPS light just came on tonight and the EPS is not working!

I was just driving earlier this evening fine, go home for an hour, hop back in the car and turn it on then the light stares me in the face.
I had already read a lot of things regarding this on the forum, took out the clock fuse and waited (realize afterwards I shouldn't have done that without grabbing the code first) that didn't work, checked battery connections, they were good.
I haven't had issues with my current battery or alternator but I really have no clue how old the battery is. It looks to be in good condition. And the charge gauge seems to always be at 14v
I had read it could also be the Main EFI relay as I have the parts but did not replace them yet. I plan on trying to retrieve a code tomorrow and then I'll replace the relay on Friday and see if that makes it go away.

Just posting to see if there is anything else I should do first or NOT do?
Cheers

 

[Old Guy]

The main EFI relay is not going to cause problems that would trigger an EPS error light.

The dash voltmeter at 14 volts would be on the low side. The 1991 service manual does not spec a voltage. The 1997 service manual infers that the voltage should be above 13.9 volts and below 15.1 volts. With a healthy electrical system most owner's report that the NSX is typically 14.5 volts to 14.7 volts. However, your reading could be due to an error in your dash voltmeter. Use a multi meter to check the voltage at the jump start terminal in the engine compartment with the engine idling. Turn on the AC with blower speed at high and headlights. If the voltage drops significantly then you may have electrical system issues that might be causing your EPS problems. However, retrieve the error codes first before doing this because some errors are not replated to the 12v system.

Your plan to drive the car again and wait until the EPS light triggers is the best plan. Take note of the driving conditions / what you were doing when the light comes on. Once the light comes on you can retrieve the error codes using the service check connector which will give you an indication of what is going on. As noted, some of those errors such as sensor errors have nothing to do with the electrical supply to the EPS.

 

[idk706]

The main EFI relay is not going to cause problems that would trigger an EPS error light.

The dash voltmeter at 14 volts would be on the low side. The 1991 service manual does not spec a voltage. The 1997 service manual infers that the voltage should be above 13.9 volts and below 15.1 volts. With a healthy electrical system most owner's report that the NSX is typically 14.5 volts to 14.7 volts. However, your reading could be due to an error in your dash voltmeter. Use a multi meter to check the voltage at the jump start terminal in the engine compartment with the engine idling. Turn on the AC with blower speed at high and headlights. If the voltage drops significantly then you may have electrical system issues that might be causing your EPS problems. However, retrieve the error codes first before doing this because some errors are not replated to the 12v system.

Your plan to drive the car again and wait until the EPS light triggers is the best plan. Take note of the driving conditions / what you were doing when the light comes on. Once the light comes on you can retrieve the error codes using the service check connector which will give you an indication of what is going on. As noted, some of those errors such as sensor errors have nothing to do with the electrical supply to the EPS.

I see. Okay I'll follow that.
When I get home from work today I'll try turning on the car today and hopefully the light will be gone.
If the EPS is still down I'd imagine it would still be mechanically safe to drive?
I'll keep this thread updated.

 

[idk706]

The main EFI relay is not going to cause problems that would trigger an EPS error light.

The dash voltmeter at 14 volts would be on the low side. The 1991 service manual does not spec a voltage. The 1997 service manual infers that the voltage should be above 13.9 volts and below 15.1 volts. With a healthy electrical system most owner's report that the NSX is typically 14.5 volts to 14.7 volts. However, your reading could be due to an error in your dash voltmeter. Use a multi meter to check the voltage at the jump start terminal in the engine compartment with the engine idling. Turn on the AC with blower speed at high and headlights. If the voltage drops significantly then you may have electrical system issues that might be causing your EPS problems. However, retrieve the error codes first before doing this because some errors are not replated to the 12v system.

Your plan to drive the car again and wait until the EPS light triggers is the best plan. Take note of the driving conditions / what you were doing when the light comes on. Once the light comes on you can retrieve the error codes using the service check connector which will give you an indication of what is going on. As noted, some of those errors such as sensor errors have nothing to do with the electrical supply to the EPS.

Afterwork today I went and shorted the connection with a paperclip and the EPS light did not turn on at all. No blinks or anything. So no code to read. I of course turned the car fully on and the EPS light was on with still no EPS active.
Now I am super unsure.
I need to go get a multimeter tomorrow and I'll test the voltage. Just wanted to update.

 

[Old Guy]

The 1991 service manual is not explicit about this; but, you have to short the service check connector then turn the ignition switch to the run position (do not start the engine) to trigger the display of the error codes.

 

[idk706]

The main EFI relay is not going to cause problems that would trigger an EPS error light.

The dash voltmeter at 14 volts would be on the low side. The 1991 service manual does not spec a voltage. The 1997 service manual infers that the voltage should be above 13.9 volts and below 15.1 volts. With a healthy electrical system most owner's report that the NSX is typically 14.5 volts to 14.7 volts. However, your reading could be due to an error in your dash voltmeter. Use a multi meter to check the voltage at the jump start terminal in the engine compartment with the engine idling. Turn on the AC with blower speed at high and headlights. If the voltage drops significantly then you may have electrical system issues that might be causing your EPS problems. However, retrieve the error codes first before doing this because some errors are not replated to the 12v system.

Your plan to drive the car again and wait until the EPS light triggers is the best plan. Take note of the driving conditions / what you were doing when the light comes on. Once the light comes on you can retrieve the error codes using the service check connector which will give you an indication of what is going on. As noted, some of those errors such as sensor errors have nothing to do with the electrical supply to the EPS.

I still have not been able to retrieve any errors with the EPS light on/still not working.
Just tested the battery itself without the car on and it's at about a 12.8 volts which i've read is fine.
I did what you said and had the car on idle, AC on max and headlights on and still had a reading of 14.7 volts with that load at the start terminals.
Not sure what it could be at this point probably the computer is bad? I've read someone here can rebuild it for me.

 

[Old Guy]

Your voltages are good.

As a Hale Mary, try resetting everything with the clock fuse, put the fuse back in then turn the ignition key to the run position and see what happens. If the EPS light immediately comes on and you cannot trigger the display of any codes with the service check connector that is kind of smelling like a controller problem.

By any chance could you have some wiring damage or modifications such that the service check connector is no longer connected to the power steering controller? There is nothing in the LHD service manual which describes a condition where the light comes on steady and does not respond to the service check connector.

Is this an Japanese market car or one one of the other RHD market cars? If it is one of the other market cars (Aus NZ ...) you may be able to get the service manual and find out whether there is something quirky about RHD cars. If it is a JDM car I expect the service manual is not going to do you much good unless your read kanji.

Short answer - its a mystery.

 

[idk706]

Your voltages are good.

As a Hale Mary, try resetting everything with the clock fuse, put the fuse back in then turn the ignition key to the run position and see what happens. If the EPS light immediately comes on and you cannot trigger the display of any codes with the service check connector that is kind of smelling like a controller problem.

By any chance could you have some wiring damage or modifications such that the service check connector is no longer connected to the power steering controller? There is nothing in the LHD service manual which describes a condition where the light comes on steady and does not respond to the service check connector.

Is this an Japanese market car or one one of the other RHD market cars? If it is one of the other market cars (Aus NZ ...) you may be able to get the service manual and find out whether there is something quirky about RHD cars. If it is a JDM car I expect the service manual is not going to do you much good unless your read kanji.

Short answer - its a mystery.

It is a RHD Japanese import
I will try resetting it again with the clock fuse.
I do not think that the service check connector is disconnected because when I first tried to use it, I did the proper steps to try and trigger a code read. 1) stick paper clip into the 2 pin connector 2)insert and turn key twice to turn on car without starting it

When I did that there no blinking lights, the EPS light does not even come on. And then when I took OUT the paper clip and turned the key twice to the on position the EPS light is there. So I can tell from that that the service connector was not disconnected.
I'm not sure what the previous owner did to this car, but it's hard for me to think he did anything as crazy as disconnecting that or any other crazy electrical jobs, who knows. I'm going to do some more research.
I went ahead and emailed Brian K at NSXE Repair to see if he still redoes units.
We'll try to keep this thread updated.
Thanks again Old Guy.