Vehicle Speed Signal Test

Fig. 23 System checker harness terminal identification:

1987---88 Accord
1. Connect test harness at ECU, Fig. 23, leaving B connector disconnected from main harness only, not the ECU.
2. Turn on ignition and measure voltage between terminals B18 (+) and A18 (-). If voltage is not approximately 10 volts, substitute known good ECU and retest. If correct voltage is available, original ECU is defective.
3. Turn off ignition and connect test harness B connector to main harness.
4. Block rear wheels and set parking brake, raise front of vehicle until drive wheels clear and support with safety stands.
5. Start engine, place manual transaxle in second speed and let out clutch, or place automatic transaxle selector at D2, then measure voltage between terminals B18 (+) and A18 (-).
6. If voltage is not approximately 10 volts above 10 mph or below 3 volts below 10 mph, check for open or short in yellow wire (terminal B18) between ECU and speed sensor amplifier. If wiring is satisfactory, replace speed sensor and recheck system.