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

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





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+)
^ B- connector pin 7 and battery negative (B-) The multimeter should be connected alternately to battery positive (B+) and battery negative (B-).

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 afresh 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.