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Help turning TCS light off after ABS upgrade

22 February 2007
Sunny SW
I'm upgrading a '92 with the late model NSX ABS modulator and after starting the car the TCS light will go on after about 8-10 sec. The TCS switch cannot toggle it off/on ... so the TCS systems itself remains off/deactivated as indicated by the dash light remaining on.

Some additional info, it's a used 2002 NSX ABS modulator (bought from a prime member) installed using the latest T3TEC harness with all new parts.

Based on other threads it said to check that everything else is working fine which they are (e.g. headlights, climate control, A/C, radio, ignition switch, etc.) and there are no ABS lights/issues after install either. Another thing recommended to check were the O2 sensors which seem fine as well (replaced 15k ago).

The codes are a 4-9 (TCS) and 3-6 (PGM-FI).

Anyone have experience or thoughts for getting the TCS to work using T3TEC? Thanks
Error code 4-9 indicates that you have complete loss of all 4 wheel speed signals. ECU error code 3-6 is indicating that the ECU is not getting the TCFC signal from the TCS controller.

The TCS gets its 4 wheel speed signals via the ABS system. On my 2000 ABS which I believe is the same design as the 2002 the wheels speed arrangement is the same. You have lost all 4 wheel speed signals so before chasing this I would confirm that the 2002 ABS wheel speed outputs are actually wired out and provided to the 1992 TCS via the T3TEC wiring harness. If they are, the fact that all 4 wheel speed signals have disappeared does not seem like a case of a single bad connector pin.

If T3TEC claim compatibility of the later ABS with the early TCS, I would start by checking the interposing wire harness to confirm that the wheel speed output signals from the ABS are actually wired through to the TCS. The wheel speed signals are pins 17 FL (ORN/BLK), 20 FR (ORN/RED), 19 RL (GRY/WHT) and 1 RR ((BLU/ORN) on the 25 pin connector on the ABS (on my 2000 ABS module). The wheel speed signals show up on pins 7 (FR), 9 (FL), 18 ((RR) and 20 (RL) at the TCS connector. The wire color assignments between the 2000 ABS and the 1992 TCS for the wheel speed signals match up which should make confirming connectivity easier. Of course, this assumes that T3TEC respected the wire color assignments on their interposing harness. You will need the service manual pin out diagram to find the pins at the TCS because Honda has adopted a very odd pin numbering arrangement on the TCS.

The service manual indicates that the wheel speed output from the ABS to the TCS is supposed to be a 0-5 volt signal pulse and this appears to be a compatible level between the 2000+ ABS and the early TCS.. If checking the wiring harness does not show a problem, then by propping the right front wheel up in the air, connect a digital voltmeter between pin 20 and ground at the ABS unit and with the ignition switch in the on position slowly rotate the right front wheel and you should see the voltmeter switch between 0 volts and 5 volts. Now go to pin 7 at the TCS and check for the signal - accessing the connector will be a hassle. If you have a signal at the ABS; but, no signal at the TCS then you likely have some kind of interposing harness problem. If the signal is making it through to the TCS, then you can check the other three wheels; but, I expect that your TCS controller might have an internal problem.

The ECU error code 3-6 appears to indicate that the ECU is not getting a confirmation signal back from the TCS on the serial data line that connects the two. This could be due to a short or open circuit in the data line or a TCS module problem or an ECU problem. The TCFC signal is on pin 32 at the TCS and the service manual describes how to check for this signal. If the signal is not present that suggests a TFC module problem. If the signal is present at the TCS then you might have a wiring problem on the data line or the ECU has an internal problem on the data line However, I would resolve the wheel speed signal problem because the wheel speed signal failure may be initiating the TCFC error code.
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