Idle Speed/Throttle Actuator - Electronic: Testing and Inspection

Fig. 23 System checker harness terminal identification:

Exc. 1987---88 Accord & 1988 Prelude
1. Connect system checker harness between ECU and wire harness coupler.
2. Connect positive probe of voltmeter to terminal A11 (green/black) and negative probe to terminal A18 (black/red) of system checker harness, Fig. 23.
3. Start engine, then measure voltage within ten seconds. Voltage should be 0.5---1.5 volts.
4. If voltage is greater than 9 volts, replace ECU. If no voltage is present, proceed as follows:
a. Check for open circuit in black/yellow wire between fuse and idle control solenoid valve.
b. Check for open circuit in green/black wire between idle control solenoid valve and ECU.
c. Check for open circuit in idle control solenoid valve.
5. Raise engine speed over 1500 RPM. If voltage is greater than 9 volts, replace ECU.
6. If, on 1987 Prelude, voltage was .5---1.5 volts in step 3, raise engine speed to above 1500 RPM and, if less than 9 volts is now available, replace ECU.