Connect a voltmeter between the removed idle air control valve plug and ground.
Turn off the ignition. The device should now show the battery voltage for 6-16 seconds (about 12 V), otherwise check fuses No.2 and 14.
If the fuses are intact, remove the relay plug (10). The relay is located in the interior space behind the lower cover, next to the steering column.
Turn on the ignition and connect the voltmeter to the ground, and also one after the other to terminals 4 and 5 of the relay plug. Then connect the voltmeter to terminals 12 (ground) and 5. The device should show the battery voltage, otherwise check the wires according to the electrical diagram.
Start the engine, insert the plug into the idle speed cut-off valve.
Connect terminals 1 and 5 on the relay plug with a short wire. The idle speed cut-off valve should engage and the engine should stop. If not, check the wire from terminal 1 to the valve for damage.
If these checks do not reveal any faults, replace the idle air control valve relay.