Captiva

DTC P0326 or P0331 - LNP or LNQ

In diesel applications high pressure common rail diesel engines are now reaching low noise operation thanks to the tight control of the pilot injection with the use of knock sensors. The knock sensors are piezoelectric devices that produce an AC voltage of different amplitude and frequency depending on the level of combustion of the pilot injection. The engine control module (ECM) monitors the knock sensor signals in order to determine if a pilot injection noise is present. If the knock system determines that excessive pilot injection is present, the ECM adjusts the pilot fuel injection quantity based on the signal from the knock sensor.

In order to differentiate between normal pilot injection, the ECM samples the knock sensor signal. The ECM samples the knock sensor signal for a certain length of time under different engine speeds and loads during non cylinder knock events. This sampling is used to determine a range of acceptable normal engine noise.

The ECM detects a knock sensor signal voltage that is not in the range of a predetermined pilot injection level in 25 of 250 test samples. The condition exists for greater than 1 s or for a cumulative of 10 s.

DTCs P0326 00, and P0331 00 are Type B DTCs.

DTCs P0326 00, and P0331 00 are Type B DTCs.

The following conditions can also set the DTC:

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine running, observe the DTC information with a scan tool. DTC P0326 00 or P0331 00 should not be set.
2. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

1. Ignition OFF, disconnect the harness connector at B68A Knock Sensor 1 or B68B Knock Sensor 2.
2. Disconnect the harness connector X1 from the K20 Engine Control Module.
3. Test for less than 5 Ω between the terminals as listed below:

•	B68A Knock Sensor 1 terminal 1 and K20 Engine Control Module terminal 31

•	B68A Knock Sensor 1 terminal 2 and K20 Engine Control Module terminal 30

•	B68B Knock Sensor 2 terminal 1 and K20 Engine Control Module terminal 32

•	B68B Knock Sensor 2 terminal 2 and K20 Engine Control Module terminal 33

⇒	If greater than the specified range, test the signal circuit for an open/high resistance.

4. Test for infinite resistance between the appropriate Knock Sensor terminal 1 and ground and between the terminal 2 and ground.

⇒	If less than the specified range, test the signal circuit for a short to ground.

5. Ignition ON, test for less than 0.3 V between the appropriate Knock Sensor terminal 1 and ground and between the terminal 2 and ground.

⇒	If greater than the specified range, test the signal circuit for a short to voltage.

6. If all circuits test normal, test or replace the B68A Knock Sensor 1, the B68B Knock Sensor 2 or the K20 Engine Control Module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.