Code 12 - Idle Speed Incorrect
Adjust carburetor idle speed and retest. Check all connections to carburetor and throttle actuator or kicker. If not equipped with vacuum throttle kicker, start test at step 3).
- If equipped with vacuum actuated throttle kicker, check for manifold vacuum at kicker at idle. If vacuum is present, stop engine and go to next step. If no vacuum is present, repair vacuum lines and retest.
- Apply 10 in. Hg vacuum to throttle actuator. Arm should extend and hold position while vacuum is applied. If not, repair or replace actuator, then retest. If actuator does operate, go to next step.
- Disconnect wiring from throttle kicker solenoid and measure resistance of solenoid. If resistance is between 45-90 ohms, go to next step. If not, replace solenoid and retest.
- Check circuit resistance between throttle kicker relay connector and solenoid, then between solenoid and ground. If resistance is less than 5 ohms, go to next step. If greater than 5 ohms, repair circuit.
- Disconnect MCU connector. Check circuits for continuity between MCU pin 12 and throttle kicker relay connector (Red/Lt Grn), and pin 20 and relay connector (Gry/Yel). If resistance is more than 5 ohms, repair circuit. If less than 5 ohms, go to next step.
- Connect ohmmeter between MCU connector pin 12 and ground. If resistance is less than 1000 ohms, repair circuit. If more than 1000 ohms, go to next step.
- Leave MCU connector disconnected. Make sure A/C switch is off. Turn ignition on and connect voltmeter across solenoid terminals (with connector on solenoid). Ground pin 12 of MCU connector and observe voltmeter. If greater than 10 volts, replace MCU module. If less than 10 volts, replace relay.