Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

Another owner contacted me with his EPS warning light.

The owner knew about the importance of
reading the error code first before resetting it
by removing the Clock 7.5A fuse or
disconnecting the battery.

So, he read the code and it was the famous
EPS #22 error code.

Also, he confirmed the parts no. of the EPS controller
and again, it was the well known problematic -023 version
guaranteed to fail at some point during the ownership.


For your reference, Acura released TSB for -033 version
for similar issue as well.
Recently, another owner contacted me with
relay issue on -305 version which already had
higher current capacity spec at one of the
two relays from the factory.


Therefore, I always replace both relays


On many forums, there are lots of owners
advising others to remove the fuse to reset the
controller even before reading the error code.

To me, it’s one of the worst advice that one can make
to other fellow owners.
Whenever you saw the warning lights,
please try to read the error code first before resetting it.


The owner lives outside of UK so we exchanged lots of
email and then the owner decided to send the controller to me.

While waiting for the delivery, I placed the order for the
higher spec relays used on the later EPS controllers.





The famous -023 version.

As seen on several EPS controllers,
there was some oxidised white powder around the case and
the connector.

Seems to be from the humidity or condensation inside
the passenger footwell area.







The problematic relays.

Basically, they can’t cope with the high current passing through
the EPS system resulting in burnt contacts and eventually
cause intermittent open circuit.







After removing the two relays, tested them on the bench.

When the power was applied to the control terminals
for the first time, both relays operated fine.







However, from the past experience,
if you switch on and off the relay rapidly or
lower the voltage, it tends to highlight the issue so
tried the frequent on-off-on testing and the relay at
RLY2 (the one at the corner of the board) showed
intermittent high resistance.







RLY1 (the one close to the centre of the board) was fine.


So, the EPS warning light that the owner experienced
from time to time was caused by this faulty RLY2.


I don’t have EPS on my NSX and also I don’t have
powerful enough bench system to test the
high current passing through the EPS controller so
I can only check the basic things within the EPS controller
and that’s part of the T&C for this service.


So, checked the 8 FETs and they seemed to be fine
although I can only do limited testing without powering up or
removing them from the board.

If the FET fails, you will feel EPS operating in one direction only
without even triggering the warning light or
some strange feedback when turning the wheel.

Also, checked the power circuit protection diode and
confirmed that there was no short circuit.







The higher current capacity spec relay at the front and
the standard one removed from the board in the back.

As you can see, the higher spec one has extra terminals.






The extra holes drilled on the board.










Because they were drilled and not through the factory etching method,
they won’t be able to create copper plated through holes so
I always strip off the coating and create extra pads
in order to get good bonding when soldering the relay terminals.

So, created the extra pads on both circuit board suffaces
and they will be solder coated later before installing the relays.


It requires delicate touch in drilling the holes at the right position and
also stripping the coating without damaging other area.


After 4hrs, my eyes and shoulder were so tired that
decided to stop for the day.


Hope to finish it very soon as I’m meeting with
another NSX tomorrow.


Kaz