Accord 1987-89
1. Start the engine at idle.
2. Disconnect the top hose from the idle air control solenoid valve from the intake manifold and check the vacuum. There must be a vacuum.
3. If there is no vacuum, check the vacuum port.
4. Stop the engine.
5. Disconnect the two-pin connector of the idle air control solenoid valve.
6. Connect the positive probe of the voltmeter to the black/yellow terminal and the negative probe to the green/black terminal.
7. 10 seconds after restarting the engine, check the idle voltage.
8. If there is voltage, replace the solenoid valve.
9. If there is no voltage - connect the positive probe of the voltmeter to the black and yellow terminal of the connector, and the negative probe to the ground wire. Within 10 seconds after restarting the engine, measure the voltage.
10. If there is no voltage - check for an open black-yellow wire between the solenoid valve and fuse number 1.
11. If voltage is detected, check the green-black wire between the solenoid valve and the computer for an open. If the wire is in order, check the on-board computer.