| CAUTION | If Engine Control Module (ECM) replacement is instructed in following test, always ensure ECM electrical connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. |
Circuit Description
Engine Control Module (ECM) operates Idle Air Control (IAC) valve to perform idle-up and provide feedback for target idling speed. DTC is set when idle speed continues to vary greatly from target speed. Possible causes are
- Defective Positive Crankcase Ventilation (PCV) valve hose or connection.
- IAC valve is stuck or remains closed.
- IAC valve circuit is open or shorted.
- A/C signal circuit is open or shorted.
- Air induction system malfunction.
- Defective ECM.
Diagnostic Aids
This DTC uses two-trip detection logic. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame records engine conditions when malfunction is detected.