DTC P0325: KNOCK SENSOR NO. 1 CIRCUIT Toyota Tundra I

Circuit Description

Knock sensor No. 1 generates voltage when engine block vibrates due to knocking. DTC is set when ECM does not receive input signal from knock sensor No. 1 with engine speed of 1500-5500 RPM. If DTC P0325 exists, ECM will operate in fail-safe mode which retards the ignition timing to a maximum setting. Possible causes are

1. Knock sensor No. 1 circuit is open or shorted.
2. Defective or loose knock sensor No. 1.
3. 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 7.1 kHz. If oscilloscope is available, knock sensor No. 1 operation may be checked by reading knock sensor signal waveform patterns with engine at 4000 RPM. Knock sensor waveform patterns may be checked by connecting oscilloscope between body ground and terminal No. 27 (Black wire) at ECM electrical connector E7. This is the KNK1 terminal on ECM. ECM is located behind glove box and heater duct. see scheme 2 For ECM electrical connector terminal identification see scheme 4 Knock sensor waveform patterns should be properly displayed. (Scheme 253)

Scheme 253

Scheme 254

Scheme 255

Scheme 256

1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Disconnect EE1 electrical connector. (Scheme 254) EE1 electrical connector is an in-line Dark Gray 3-pin electrical connector located near the cylinder head.
2. Note wire terminal identification in male side of EE1 electrical connector. (Scheme 255) Remove wires from terminals No. 1 (Black wire) and 2 (Gray wire) in male side of EE1 electrical connector. Reverse wire location for terminals No. 1 and 2 and reinstall wires in male side of EE1 electrical connector. Reconnect EE1 electrical connector.
3. Turn ignition on and then turn hand-held tester or scan tool on. Using Toyota hand-held tester or scan tool, clear DTCs from ECM. Start engine and warm engine to normal operating temperature. Suddenly accelerate engine to 4000 RPM for 3 times. Recheck for DTCs. If DTC P0325 still exists and DTC did not change from original DTC of P0325, go to next step. If DTC changes from original DTC of P0325 to P0330, go to step 5.
4. Check for open and short in wiring harness and electrical connectors between EE1 electrical connector and ECM for knock sensor No. 1. See WIRING DIAGRAMS article. ECM is located behind glove box and heater duct. see scheme 2 If wiring harness or electrical connector is defective, repair as necessary. If wiring harness and electrical connectors are okay, replace ECM.
5. Check for open and short in wiring harness and electrical connectors between EE1 electrical connector and knock sensor No. 1. See WIRING DIAGRAMS article. Knock sensor No. 1 is located on cylinder block, just below cylinder head. (Scheme 256) If wiring harness or electrical connector is defective, repair as necessary. If wiring harness and electrical connectors are okay, replace knock sensor No. 1. See KNOCK SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.