Vehicle Speed Signal Circuit Troubleshooting

1986-87

Integra

This signal informs the ECU when vehicle speed exceeds 10 mph.
1. Connect system checker harness between ECU and wire harness connector. Disconnect ``B'' connector from main wire harness only, not from ECU.
2. Position ignition switch to On position, then measure voltage between terminals B18 (+) and A18 (-) of system checker harness. Voltage should be approximately 5 volts. If voltage is as specified, proceed to next step. If voltage is not as specified, substitute a good ECU and recheck voltage. If voltage is now as specified, replace ECU.
3. Turn ignition switch Off, then reconnect ``B'' connector to main wire harness.
4. Raise and support front of vehicle, then apply parking brake and block rear wheels.
5. Start engine, place transmission in 2nd gear (D2 on automatic equipped vehicles), then measure voltage between terminals B18 (+) and A18 (-). Voltage should be below 3 volts at speeds below 10 mph, or at battery voltage at speeds above 10 mph.
6. If voltage is as specified, vehicle speed signal is OK. If voltage is not as specified, repair open or short in yellow/white wire between ECU and speed sensor amplifier. If wire is OK, replace speed sensor.