| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES - IMPORT article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT. |
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
Knock sensor is located on side of engine block, under intake manifold. Knock sensor generates voltage when engine block vibrates due to knocking. DTC is set when there is no knock sensor signal to ECM with engine speed at 2000 RPM or more. If DTC P0325 exists, ECM will operate in fail-safe mode which retards the ignition timing to a maximum setting. Possible causes are
- Knock sensor circuit is open or shorted.
- Defective or loose knock sensor.
- Defective ECM.
Diagnostic Aids
Normal mode vibration frequency of knock sensor is 7.6 kHz. Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.