SAAB WIS ONLINE

P0331

Symptom: Engine performance may be down

P0331

Knock sensor for cylinders 2-4-6: no input to control module/no continuity or short circuit


Fault symptom

Engine performance may be down

Condition

The input from the knock sensor is active or absent for more than four seconds at engine speeds above 1800 rpm.

Diagnostic procedure


1. Use the ISAT command "KNOCK CONTR ACTIVE" in the "READ ON/OFF" menu or the "KNOCK CONTROL" command in the "READ FUNCTIONS" menu while driving the car with the engine labouring heavily.

The ISAT should then show how many degrees the control module retards the ignition when knocking occurs. If ignition retardation takes place, proceed to point 7.

If no retardation of the ignition is shown in spite of the engine being made to work hard, continue with the next point.

2. Check that the knock sensor connector makes good contact.

3. With the ignition switched off, connect a BOB between the MOTRONIC control module and the wiring.



Start the engine and check the knock sensor's signal voltage by taking a reading across 29 and 30 on the BOB. When the engine is revved up, the voltage should be higher than 20 mV∼.

If the voltage is OK, proceed to point 5. If it is not, continue with point 4.

4. Check the screened lead between the knock sensor and pin 29 of the control module for continuity/shorting.

5. Check that the knock sensor is tightened to a torque of 22 Nm (16 lbf ft).


6. Then check the knock sensor signal by measuring the voltage directly on the sensor while lightly tapping the knock sensor retaining screw. The voltage should then go up to at least 100 mV∼.


If no voltage is obtained (the knock sensor appears to be completely "dead"), change the sensor.

7. Clear all trouble codes and drive the car on the road to check whether any codes are generated afresh. If they are, turn to for further diagnostic instructions.