P0327

KNOCK SENSOR





Symptom Of Fault.
The car runs on basic boost pressure only, continuous ignition retard.

NOTE: The Saab Trionic system does not have a conventional knock sensor. The signal comes from the ignition discharge module.

Conditions.
^ Engine running.
^ No knock signal for 10 seconds.

Diagnostic Help.
A knock signal reading can be obtained using an ISAT scan tool.
- Select "READ FUNCTIONS".
- Select"KNOCK SENSOR".

The ISAT scan tool should show a reading of between 0.0 V and 2.55 V, depending on the level of the knock signal.
At idling speed the ISAT scan tool should show a reading of 0.06 to 0.16V.
If the throttle is opened suddenly, the ISAT scan tool could show a reading of 0.06 to 2.55V.

In the event of a break in the signal lead connected to pin 44 of the control module, a reading of 0.06 to 0.08V will normally be obtained whatever the throttle opening.

Checking The Wiring.
Intermittent faults may occur as a result of occasional short circuits and breaks in the wiring. Jiggle the leads and in-line connectors at several places and in different directions to reveal faults in the wiring harness. Observe the multimeter, ISAT scan tool or test lamp while carrying out this check.





Diagnostic Procedure.
1. Check the electrical interface

- Ignition switch in ON position.
- Unplug the ignition discharge module's 10-pin connector.
- Connect a multimeter, set for d.c. voltage, to
^ Connector pin 7 and battery positive (B+)
^ Connector pin 7 and battery negative (B-)

The multimeter should be connected alternately to battery positive (B+) and negative

When connected to battery positive (B+), the meter should indicate a positive voltage (about 6-12 V) which rapidly drops to 0 V.

When connected to battery negative (B-),the meter should indicate a negative voltage (about -6 to -12 V) which rapidly rises to 0 V.

Are the readings obtained OK?
YES: Continue with point 3.
NO: Continue with point 2.





2. Check the knock signal's lead

- Check the continuity of the lead between pin 7 of the ignition discharge module and pin 44 of the control module.
- Check the lead for open circuit and shorting.

Are the test readings OK?
YES: Continue with point 3.
NO: Rectify the fault and proceed to point 3.





3. Final check:

- Clear the diagnostic trouble code.
- Implementation of driving cycle: Drive the car at varying engine loads and rpm for 5 minutes.
- Evaluation of driving cycle:
Check whether the diagnostic trouble code has recurred.

Has the diagnostic trouble code recurred?
YES: Try fitting a replacement ignition discharge module and, after a repetition of the driving cycle, check whether the diagnostic trouble code is generated afresh.
NO: The remedial measure taken was correct.

Has the diagnostic trouble code been generated a fresh after changing the ignition discharge module?
YES: Refit the original ignition discharge module and then continue at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO: Scrap the original ignition discharge module. The remedial measure taken was correct.