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 1500-6000 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 8.1 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. 18 (Gray wire) at ECM electrical connector E7. This is the KNKL 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 277)

Scheme 277

Scheme 278

Scheme 279

Scheme 280

Scheme 281

1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. see scheme 1 Disconnect EC1 electrical connector on 4WD models or EC2 electrical connector on 2WD models. (Scheme 278) EC1 electrical connector is an in-line Dark Gray 6-pin electrical connector located near the starter. EC2 electrical connector is an in-line Gray 3-pin electrical connector located near the starter.
2. Note wire terminal identification in male side of EC1 or EC2 electrical connector. (Scheme 279)and (Scheme 280). On 2WD models, remove wires from terminals No. 2 (Black wire) and 3 (Gray wire) in male side of EC2 electrical connector. Reverse wire location for terminals No. 2 and 3 and reinstall wires in male side of EC2 electrical connector. Reconnect EC2 electrical connector. On 4WD models, remove wires from terminals No. 2 (Black wire) and 3 (Gray wire) in male side of EC1 electrical connector. Reverse wire location for terminals No. 1 and 2 and reinstall wires in male side of EC1 electrical connector. Reconnect EC1 electrical connector.
3. On all models, 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 EC1 or EC2 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 EC1 or EC2 electrical connector and knock sensor No. 1. See WIRING DIAGRAMS article. Knock sensor No. 1 is located below intake manifold on cylinder block. (Scheme 281) 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.