EPS failure

[03 raw nsx]

Hey Guys...I stalled my car yesterday. Then after startup my EPS light came on. Tried resetting the clock fuse and checked ground on battery, no help. Anyone have other solutions to reset EPS?

 

[Old Guy]

Hey Guys...I stalled my car yesterday. 郎 Then after startup my EPS light came on. Tried resetting the clock fuse and checked ground on battery, no help. Anyone have other solutions to reset EPS?

If the EPS light remains illuminated after pulling the reset fuse that suggests that the error causing the problem persists. Trigger the display of the stored error codes using the service check connector. The error codes will give you some clue as to what is going on.

 

[03 raw nsx]

If the EPS light remains illuminated after pulling the reset fuse that suggests that the error causing the problem persists. Trigger the display of the stored error codes using the service check connector. The error codes will give you some clue as to what is going on.

Trouble shot the EPS failure using the service manual flow charts, everything checks out fine but the light is still on. Then tried looking for error codes, no codes. Could a 'spike' in voltage blow the EPS control unit?

 

[Old Guy]

I take it that you used the procedure for triggering a code display with the service check connector and nothing happened? I am also assuming that the EPS is non functioning? If so, get a hold of a paper copy of the service manual. You need a paper copy since I recall that the freely available .pdf of the 1997+ service manual is missing large portions of the steering section. My hard copy service manual is tucked away in my trunk in a storage compound so I can't access it. As I recall, in the trouble shooting section there is a specific line in the chart for dealing with the problem where the EPS light comes on and stays on after start up; but, there is no stored error code.

 

[03 raw nsx]

I have a 'hard copy' of the service manual. I purchased it as soon as I purchased my car.

Yes, I did follow the flow chart for 'EPS light stays on after start' every check goes to the next 'yes'. At the end it tells you to try another EPS Control unit.

The start of the problem was the initial stall of the car, then as I am driving I could hear a relay or something 'clicking' while I'm driving behind my seat. Also my CEL was on. When I got home I found my negative terminal was loose and intermittently connecting. Upon securing the negative terminal, the CEL went off, but the EPS stayed one. That is when I got the manual out, but no help. Maybe the intermittent battery cable fried the EPS Control unit. Thoughts?

Rich Wong

 

[Old Guy]

There is a unit called the pulser (or something like that) that resides behind the driver's back seat. Its on non automatic equipped NSXs and takes the speed signal from the sensor used by the automatic transmission and converts it into a speed signal for use by the EPS. This conversion function was originally done by the controller for the automatic transmission. I don't know why the EPS needs this speed signal plus the VSS1 speed signal. I remember a few years ago that there was a post by somebody complaining that their pulser was making clicking noises. Perhaps something has happened to your pulser unit which has resulted in loss of the VSS2 signal; however, I would have thought that there would be a specific error code for something like that. But, since the pulser is the only EPS component behind the driver's seat that I know of it might be worth checking out to see if there is a problem with it.

I understand why a stall or bad electrical connections that cause low voltages can trigger an error in the EPS. When the supply voltage is low the motor draws more current to generate the same torque and the controller has sensors to limit the current and trigger a shut down and error codes. It is not obvious how a low voltage would damage electronic (semi conductors) components. Operation may become erratic or cease while the voltage is low; but, everything generally recovers when the voltage returns to normal. In some cases, with high current you might get fatal damage to the two relays in the EPS unit if those connections have already deteriorated. That relay problem usually generates a specific error code (I can't remember which it is). You might be able to search for that or go to Kaz's blog where he covers the EPS relay problem in some detail. The interesting thing about the relay problem is that Honda switched back and forth between different style relays so some intermediate year cars are less prone to problems and then some late cars are back to having the problem (as I recall). Kaz had a listing of the EPS controller part numbers that are prone to the problem and those that are not so prone to the problem. Worth checking out.

Edit:
Here is the thread talking about noise from 'somewhere around the pulse unit'. Not super helpful.

http://www.nsxprime.com/forum/showt...nit-clicking?p=1944980&viewfull=1#post1944980

As an aside, what is the voltage in your car when you are cranking the engine? Is it dropping below 10 volts which is indicative of a failing battery? The reason I ask is last spring when I took my car out of storage I had a weird problem with the rear hatch closed indicator on the dash staying lit even though the hatch was closed (prevented arming of the security system). I chased the problem for a few days and then my 8yr old battery went dead. I replaced the battery and the indicator problem went away. The problem was not the battery cable clamps because I cleaned them when I connected the battery coming out of storage. Prior to the battery dying the car voltage was always > 14 volts when running and that didn't change after replacing the battery. I have no explanation for how changing the battery fixed the problem; but, the strange thing is that two other owners reported similar problems and the same fix. Just another thing to check since we are in the Hail Mary mode.

 

[03 raw nsx]

As an aside, what is the voltage in your car when you are cranking the engine? Is it dropping below 10 volts which is indicative of a failing battery? The reason I ask is last spring when I took my car out of storage I had a weird problem with the rear hatch closed indicator on the dash staying lit even though the hatch was closed (prevented arming of the security system). I chased the problem for a few days and then my 8yr old battery went dead. I replaced the battery and the indicator problem went away. The problem was not the battery cable clamps because I cleaned them when I connected the battery coming out of storage. Prior to the battery dying the car voltage was always > 14 volts when running and that didn't change after replacing the battery. I have no explanation for how changing the battery fixed the problem; but, the strange thing is that two other owners reported similar problems and the same fix. Just another thing to check since we are in the Hail Mary mode.

Well my battery is in great shape, I'll try leaving it on a trickle to top it off. And see what happens.

Do you think I can remove the EPS control unit and drive the car without causing any problems? I want to send the unit off to Brian K, so he can check it out. Thoughts?

 

[docjohn]

you can drive without eps just fine....will also build up some arm muscles:wink:

 

[03 raw nsx]

Problem Solved...replaced EPS Control Unit.
Now the real detective work will be done by BrianK. I sent the bad EPS control unit to him for repair.

 

[docjohn]

always good to have spares...like the main relay.

 

[03 raw nsx]

always good to have spares...like the main relay.

Yea...but the EPS Control Unit can be a $2k spare :tongue:
Or in my case from www.amayama.com only $1,300.

 

[docjohn]

wow that is pricey for a little box....unless its blue......

 

[03 raw nsx]

wow that is pricey for a little box....unless its blue......

And she deserves it...:smile:

 

[docjohn]

Not to go too far OT....but the little blue box was a little too pricey for the richest man in Europe....so he got a little break....

 

[Old Guy]

Problem Solved...replaced EPS Control Unit.
Now the real detective work will be done by BrianK. I sent the bad EPS control unit to him for repair.

It will be interesting to hear what Brian K determines is the nature of the failure. Given the way it failed I am inclined to think relays; but.....

Did you check the part number on your original unit to see if it was in the range that had known relay problems?

 

[03 raw nsx]

I didn’t check the part number...I was not aware of EPS control units with known problems. Do you have more info on which EPS control units have issues? I can’t check since I’ve already sent mine to Brian.

 

[Old Guy]

I didn’t check the part number...I was not aware of EPS control units with known problems. Do you have more info on which EPS control units have issues? I can’t check since I’ve already sent mine to Brian.

This is a brief overview

http://www.nsxprime.com/forum/showt...-Please-help?p=1766514&viewfull=1#post1766514

Kaz mentions a couple of the production numbers that have known problems.

I recall that on his blog Kaz discusses the production change in the EPS unit relays going from the single pin to 3 pin connectors and I seem to recall that later EPS units went back to a single pin connector. Your being a 2003 might have that later controller. It has been 3 or 4 years since I read that post by Kaz so the exact details are fuzzy. If you want the full break down on the production numbers you would have to go through his blog threads that he linked in that post.

Edit: This is a link to the blogs where Kaz discusses failure on later cars.

http://www.nsxcb.co.uk/blog.php?1811&blogcategoryid=47