Electronics/Speedometer question

[ktan]

So I'm trying to see if there are any wiring experts out there. This may get complicated so it I'll explain the situation first.

I have a 1995 OBD II NSX that was converted back to OBD I and throttle cable so that I can utilize an AEM for FI. In order to approach the conversion, I used a 91-94 (specifially a 93) engine harness and changed the appropriate plugs for my 95. EVERYTHING WORKS ... except my speedometer. The RPMs, Oil Pressure, voltage, etc. all work except the speedometer.

Notes:
1. The speed sensor is connected, but there is one more plug on my 93 harness that does not plug into my 95 transmission.
2. By the ECU there are 5 plugs that go into the ECU, 2 blue plugs and 2 grey plugs. Only ONE of the Grey harness plugs from the 93 harness plugs into the 95 interior harness.

Questions:
1. First of all, I am wondering if the cluster is different for these years, particularly the wiring for the speedometer in the cluster.
2. Is the Speed sensor different in 91-94 cars?
3. Anyone know what the other sensor on 91-94 cars is? My 95 has a place for this sensor but it is covered by a plate.
4. Anyone have the electrical manuals for both 91-94 cars AND 95 cars?

I have DEFI gauges, and I'm tempted to just buy the Defi Link unit with digital speedometer and run a wire to my speed sensor!

Thanks
Kevin

 

[lithiumus]

I haven't taken a good look at the manual, but have a look at the wiring pins / connectors and find the speedometer input to the cluster. Not sure what the signal should be but most likely voltage.

Have someone help you out. Connect a test lead to that wire and measure voltage while driving. If there is proper voltage, you most likely have a problem with the cluster i.e. incompatability, etc. If you don't have a signal, you know you have connectivity issue in between the sensor, ECU, cluster.

Have a look at the scematics in the Service manual to verify. You should have a copy of the 95 service manual so you can confirm any differences between the 93 vs. 95.