EPS code 31 & 33 - was EPS & TCS strange behaviour.

To recap. I had odd behaviour from warning lights that was resolved by replacement of clock fuse - thanks Larry!
http://www.nsxprime.com/forum/showt...our-from-EPS-and-TCS-warning-lights?p=1694930
On replacing the fuse, I could pull the codes and there was a problem with the steering. Codes 31 and 33. 31 involves the ignition switch, and 33 the VSS speed sensor.

I finally got a replacement sensor, fitted it, and went for a run today. No change. Speedo works fine, so I guess I installed it ok. Pulled codes again, and still getting 31 and 33.

As the VSS is new (and hopefully known good!) and code 33 has re occurred, does that mean there is an issue with the EPS ECU, or do I need to replace the ignition switch before I can make this call?

Car is a UK model 1995 Targa.

Cheers in advance for any help!
Matt

Hi, Matt.

If your speedo was working fine before replacing the VSS, then I’m afraid it is very unlikely to fix the EPS code #33 by replacing it.

Based on the other thread linked above, it looks like you have UK spec 95 NSX-T with 6MT installed.
Not sure whether it was originally 5MT or 4AT converted into 6MT and also I don't know the spec of your 6MT box.


First, if you got EPS #31, please check the condition of your battery, the battery cable and the actual connectors at the EPS controller.
Once the engine has started, ACG will provide enough power but with the bad battery or poor connection at the battery posts or at the controller, it will trigger several issues.


Code #33 is triggered by the speed difference exceeding the allowed window between the VSS1 (the one you replaced) and the VSS2 (the small pick up near the VSS, monitoring the DF/final ring gear speed).

If your NSX is MT, then the VSS2 signal is conditioned inside the small ‘Pulse Unit’ above the TCS controller and if your NSX is AT, then the VSS2 is generated inside the AT controller using the NC (counter shaft speed) sensor.

The EPS controller on 95 model is not that sensitive to the VSS1/VSS2 speed difference compared to the later spec controller so if it triggered the #33 code, you should be able to find the cause fairly easily.
It could be the DF (VSS2) sensor itself, pulse unit, cable issue or simple as the connector not fully locked.
You can find the VSS2 check procedure in the workshop manual under EPS section.

By the way, are you using the standard final ratio?

Some owners installed Type-R or aftermarket final gear on the EPS equipped NSX and because the ring gear diameter was slightly larger than the original one, it managed to hit the DF sensor head (VSS2 sensor) slightly and eventually, it scraped off enough amount and no more sensor signal.
Type-R didn’t have EPS from the factory so this issue didn’t happen until people started using its final gear on EPS model.

For your reference, under EPS code #33, you won’t loose the power assist even with the EPS warning light on the dash.
The software will just stop the speed dependant control loop and just keep the system in full assist mode until you switch off the car.


As a side note, if your NSX is UK 95 model, you are very likely to have ver. -023 EPS controller.

I’m afraid this one will trigger EPS code #22 sooner or later because simply the internal relay doesn’t have enough capacity to cope with the huge current apssing through the EPS system.

You can read all the stories in my blog on NSXCB site here;
http://www.nsxcb.co.uk/blog.php?1811&blogcategoryid=47


Kaz

Wow. Great reply, thanks.

Kaz-kzukNA1 said:

Hi, Matt.

If your speedo was working fine before replacing the VSS, then I’m afraid it is very unlikely to fix the EPS code #33 by replacing it.

Based on the other thread linked above, it looks like you have UK spec 95 NSX-T with 6MT installed.
Not sure whether it was originally 5MT or 4AT converted into 6MT and also I don't know the spec of your 6MT box.

Click to expand...

Yep, UK car, originally 5MT, but I stuck a 6 in as I was fed up of paying for the clutches - car has done over 220k miles. Light fly, single plate clutch, and all original 6MT internals. Box is marked E6E if that helps. Swap was done about 3 years before the EPS issue raised its head.

Kaz-kzukNA1 said:

First, if you got EPS #31, please check the condition of your battery, the battery cable and the actual connectors at the EPS controller.
Once the engine has started, ACG will provide enough power but with the bad battery or poor connection at the battery posts or at the controller, it will trigger several issues.

Click to expand...

Battery is good, and I've replaced the earth cable. I visually checked the EPS controller connectors, and could see no issues, but I'm no auto-electrician.

Kaz-kzukNA1 said:

Code #33 is triggered by the speed difference exceeding the allowed window between the VSS1 (the one you replaced) and the VSS2 (the small pick up near the VSS, monitoring the DF/final ring gear speed).

If your NSX is MT, then the VSS2 signal is conditioned inside the small ‘Pulse Unit’ above the TCS controller and if your NSX is AT, then the VSS2 is generated inside the AT controller using the NC (counter shaft speed) sensor.

The EPS controller on 95 model is not that sensitive to the VSS1/VSS2 speed difference compared to the later spec controller so if it triggered the #33 code, you should be able to find the cause fairly easily.
It could be the DF (VSS2) sensor itself, pulse unit, cable issue or simple as the connector not fully locked.
You can find the VSS2 check procedure in the workshop manual under EPS section.

Click to expand...

Could you give me the page ref for the vss2 check procedure? I can't find it in the manual I have. What does the pulse unit look like?

Kaz-kzukNA1 said:

By the way, are you using the standard final ratio?

Some owners installed Type-R or aftermarket final gear on the EPS equipped NSX and because the ring gear diameter was slightly larger than the original one, it managed to hit the DF sensor head (VSS2 sensor) slightly and eventually, it scraped off enough amount and no more sensor signal.
Type-R didn’t have EPS from the factory so this issue didn’t happen until people started using its final gear on EPS model.

For your reference, under EPS code #33, you won’t loose the power assist even with the EPS warning light on the dash.

The software will just stop the speed dependant control loop and just keep the system in full assist mode until you switch off the car.

Click to expand...

After a reset, the EPS light clicks on after the speed exceeds 20mph, but the power assistance remains while I leave the ignition on. After turning the car off and then on again, the EPS light comes on instantly and there is no power assistance.

Kaz-kzukNA1 said:

As a side note, if your NSX is UK 95 model, you are very likely to have ver. -023 EPS controller.

I’m afraid this one will trigger EPS code #22 sooner or later because simply the internal relay doesn’t have enough capacity to cope with the huge current apssing through the EPS system.

You can read all the stories in my blog on NSXCB site here;
http://www.nsxcb.co.uk/blog.php?1811&blogcategoryid=47
Kaz

Click to expand...

Wow. I'll wait till I have a quiet moment and read that fully!
Cheers
Matt

Hi, Matt.

I looked at the manual available through the NSX Wiki and I noticed that some of the pages including the EPS ones are missing.
I have 10’s of NSX manuals but they are all in Japanese. I guess you don’t speak Japanese, do you???

It’s only 3 pages but with lots of diagrams included so when I have some extra time, I will translate them and send it through PM or email (if you have enabled it).

Kaz

I'm linking to my recent EPS-light experience to make future diagnoses easier by tying the threads together.

Hi Matt, I have a 1995 Targa Auto. My EPS light has come on and Power Steering doesnt work. Speedo works one minute then stops. When i pull out the clock fuse and put it back in all works again, but not for long. I had the dealer tell me the fault code i was getting was 31. It's soemthing to do with the ignition but i dont know what it is. Do you have any idea? I am actually a Honda Motorcycle Dealer in Australia, but dont have any access to Honda cars. I am guessing that after 25 years on the road and travelled 318,000 kilometres i can expect the odd problem. If you can help i would appreciate any help. Cheers, Eddie Peters.

Eddiep said:

Hi Matt, I have a 1995 Targa Auto. My EPS light has come on and Power Steering doesnt work. Speedo works one minute then stops. When i pull out the clock fuse and put it back in all works again, but not for long. I had the dealer tell me the fault code i was getting was 31. It's soemthing to do with the ignition but i dont know what it is. Do you have any idea? I am actually a Honda Motorcycle Dealer in Australia, but dont have any access to Honda cars. I am guessing that after 25 years on the road and travelled 318,000 kilometres i can expect the odd problem. If you can help i would appreciate any help. Cheers, Eddie Peters.

Click to expand...

Not sure if you've seen this other thread but I have this same issue, post #46 here (http://www.nsxprime.com/forum/showthread.php/179685-EPS-Electronic-Power-Steering-Please-help/page2).

I had codes 31 and 33, if you just had 31 then I'd think it would be a battery/ground/wiring issue, but since your speedo is also intermittent then I would think it might also be the speed sensor VSS1 that's gone bad or the connector is problematic. Maybe the dealer missed the 33 code. Kaz's explanations here and in that thread are good reading.

Since you have an auto, the VSS1 is a different style than the manual's version. Both VSS1 and VSS2 are on the side and top of the transmission and look the same, but they have different part numbers (not sure if it's just wiring length or not). There are fairly cheap aftermarket versions available if you're so inclined. That's what I'm replacing right now to see if it fixes the EPS codes for good.

EDIT: Above not true, autos have the VSS1 as normal, plus an NC and NM speed sensor. NC is "VSS2" in manual trans parlance.