Freaky Dash Cluster Antics on NSX with Automatic Transmission

[Foxlovescars]

1991 Automatic

1991 Automatic

Lately, my red EPS (electric power steering light, for those of you with manual trannys), has been coming on after I drive a few miles. My power steering then reverts to manual. If I am driving over 60 mph or so when this happens, the "D" green indicator drive light in the cluster starts to blink, and my speedo indicator will actually bounce up and down to zero and back again to the speed I am traveling. When I slow down, say, on an exit ramp, the speedo indicator stops bouncing and registers the correct speed. The green "D" light will still continue to blink.

I would guess, this is something the car does purposely to alert you of a particular problem. I have looked throughout the 23 chapters of my service manual and have not found anything explaining what this action is suggesting that I do.

Of course, when I stop the car and turn off the ignition, or if I disconnect the negative battery cable the problem USUALLY goes away. Also, if I pull the 7.5 amp clock fuse the system resets itself as well. The EPS light doesn't come on EVERY time, maybe 50% of the time while I am driving.

Does anyone have any ideas?

Thanks for your time and your help,
Frank

 

[Old Guy]

The EPS is notoriously sensitive to low voltage. The first thing to check is the + battery cable to make sure that it is securely fastened (I am going to assume that the - is OK because you disconnected and reconnected it). Honda battery post connectors have a reputation for getting over tightened and stretched by over enthusiastic wrenches. The result is the clamp doesn't grip the post leading to poor connections and all kinds of intermittent electrical problems.

The other clue may be the bouncing speedometer needle. That could be a bad electrical connection or a sign that the VSS speed sensor is failing. Check your service manual; but, the post 1997 NSX EPS has a speed signal as an input. If the VSS or the signal from the VSS is flaking out on you, that may be causing your problem. Also, check the service manual - I thought the EPS has a procedure for retrieving diagnostic trouble codes which may provide some guidance.

I don't have a clue about the blinking Drive indicator light.

 

[Kaz-kzukNA1]

From what you wrote, looks like it's VSS signal related but please first read the error code by shorting the SCS terminal at the passenger footwell before resetting the system or disconnecting the battery.

If you had any services recently around the eng bay, I would first check the connector of VSS at the gbox.
If it’s fully locked, you could check the sensor signal by rotating the rear wheels but probably quicker to just replace it.
You can use OEM parts but also many owners had good experience using non-OEM one from reputable companies.
VSS signal spec on any JDM cars are defined in JIS so usually, same sensor is shared with different models and thus, reduces the cost.

VSS is one of the key input for the EPS and it’s being compared against another signal generated by the AT controller (on MT, there is a pulse generator box instead) so if it detects abnormal condition, it will trigger EPS light with code #33 .

Bouncing speedo is typical phenomenon when VSS fails.

Blinking D indicator is from the AT controller.
Again, VSS is one of the sensor input and if it detects failure, it will trigger blinking D as the AT related warning light. You probably triggered code #4 .

So, first thing first, please read the error code.


Kaz

 

[Foxlovescars]

Thanks for the input Old Guy and Kaz-k. You touched on a lot of things that I will check out one-by-one. The car drains the battery in a week's time if I don't drive the car. A battery is always the cheapest starting point for any intermittent problem. I'll test the SCS terminal in the glove box and check for codes.

As usual, you guys that take the time to answer our questions on the forum are the best!

Thanks,
Frank

 

[Old Guy]

If you need a new battery, you need a new battery! But, if doing the cheapest thing first is your criteria, an aftermarket VSS can be pretty cheap. I have seen the VSS for the later model manual transmission NSX listed for less than $10 on EBay. Can't comment on the quality; but, sometimes the inexpensive stuff from China is just fine. I have a Chinese MAT sensor on another car that has been working just fine for a couple of years.

When you pull the error codes, you should get a sense of the direction to go in.

 

[furinax]

I think Kaz was on point. You can get a pretty cheap Accord VSS (you can find the part number by searching forums) to fix the bouncing speedo issue. I'm not saying that's the problem but it's a pretty cheap and easy fix and if the EPS relies on that, then it fixes all the problems. Interesting to note that your odometer does not go up if your VSS is out.

I had mine fixed last year with an Accord part and it works fine. It is always a good thing to find the right solution but if you have a choice go for the cheaper one. =)