| 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
Knock sensor generates voltage when engine block vibrates due to knocking. Knock sensor may also be referred to as knock sensor No. 1. DTC is set when ECM does not receive input signal from knock sensor with engine speed of 1200 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
Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.
Normal mode vibration frequency of knock sensor is 6.6 kHz. If oscilloscope is available, knock sensor operation may be checked by reading knock sensor waveform patterns with engine at 4000 RPM. Knock sensor waveform patterns may be checked by connecting oscilloscope between body ground and terminal No. 28 (Black wire) at ECM electrical connector E8. This is the KNK1 terminal on ECM. ECM is located behind glove box. see scheme 2 For ECM electrical connector terminal identification see scheme 4 Knock sensor waveform patterns should be properly displayed. (Scheme 111)
Scheme 111
- Ensure ignition is off. Remove glove box for access to ECM with electrical connectors still installed on ECM. see scheme 2 Disconnect ECM electrical connector E8. see scheme 4
- Using ohmmeter, check resistance between body ground and terminal No. 28 (Black wire) at ECM electrical connector E8. see scheme 4 This is the KNK1 terminal on ECM. Resistance should be one megohm or higher. If resistance is not within specification, go to next step. If resistance is within specification, go to step 4.
- Check knock sensor. See «KNOCK SENSOR»(ref-133221-S09438602572002021900000) under ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If knock sensor is okay, go to next step. If knock sensor is defective, replace knock sensor.
- Check for open and short in wiring harness and electrical connectors between knock sensor and ECM. See «WIRING DIAGRAMS»(ref-133228) article. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
- Replace original knock sensor with a known-good knock sensor. See «KNOCK SENSOR»(ref-133226-S04347412862002021900000) under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article. Clear DTCs from ECM and then recheck for DTCs. If DTC P0325 does not exist, original knock sensor was defective. If DTC P0325 still exists, replace ECM.