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Today at Atelier Kaz - Private NSX Enthusiast, ex-Honda R&D engineer with F1, Indy/CART background

EPS Controller Service 01

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Wanted to make some changes in the rhythm so decided to work on the EPS controller that another owner sent in recently.

Following on from my research on the EPS controller issues with version -023, -033, -305 models, I started to hear several issues on the later spec -043 model as well.
I think it is now superseded to different model.


As it was not that popular to have EPS warning light with 043 version at that time, I requested the owner to check the usual things such as the battery health, battery terminal connections, GND fixing point, EPS rack connector, EPS controller connector and being reported that all looked to be fine.

Then, the owner reported that he was getting EPS error code #22 when he kept the steering wheel at full lock position so asked him to send in the controller to me.
You can see both relays went back to the standard current capacity spec and the castle like object at the centre of the 1st photo is the current measure device
converting sensed current into voltage level.








Long-long time ago, another owner sent in his 043 version controller with intermittent EPS warning light.

He was getting EPS error code #4 from time to time so not easy to re-create the same issue.


It is related to the Current Offset so for this one, I felt it was more to do with something outside of the EPS controller.
For example, rusty commutator inside the EPS rack, etc.


As it was sort of spare unit for the owner, I didn't put high priority but now that I had another 043 controller here, decided to take a look at it at the same time.
The board colour was different from the above one and based on the serial no., this one is from the later batch.








I already knew that for some reason, Honda decided to go back to the standard spec relays for 043 controller when they once replaced at least one of the relay to the higher current spec one previously.

So, removed both relays and tested them on the bench.

Once again, it was the burnt relay contact on the RLY #1.
When it was activated, it was showing random resistance from almost 0.0ohm upto several meg ohm.


On the other board with intermittent EPS error code #4, I didn't notice any issues with both of the relays but since it's intermittent failure, who knows.
Sooner or later, the relay will fail any way so I'll install the higher current capacity spec relays on this board later.






Checked the state of 8 x FETs, 1 x Trns and lots of diodes on both boards with no issues so far.
As far as I can see, there was no acid leakage from the electrolytic caps.



As Honda changed the current sensing circuit and new board design, spent some time confirming that it is not using multi layers circuit board and simply top and bottom layer used.
You don't want to drill the hole on the circuit board only to find that you have cut through the internal track layer.



Will start drilling the holes shortly but I'll first go back working on the NSX inside the garage.

More to follow later.

Kaz




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