LEMON Manuals: Even more car manuals for everyone
Home >> Saab >> 2001 >> 9-5 Base, 4D Sedan, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Fault Code Diagnosis >> P0302: Cylinder 2 Misfire Detected >> Fault Isolation Procedure

Fault Isolation Procedure

  1. Check additional DTCs in the ECM system:
    • Turn the ignition switch to the ON position.
    • Contact ECM.
    • See whether any of the following DTCs have been recorded: DTCs P1300-P1306, DTCs P1390-P1396.
    If any of the above trouble codes are present, go to the relevant fault isolation procedure. If none of the above codes are present, go to next step.
  2. Check additional DTCs: If DTC P1676 has been recorded, follow the fault isolation procedure given for it, otherwise go to next step.
  3. Checking cylinder compression:
    • Read Freeze Frame and make note of the following data: Engine RPM, Airmass / Combustion and Coolant Temperature.
    • Check the cylinder compression.
    If the function is correct, go to next step, otherwise rectify the fault and go to step  11.
  4. Checking the ignition coil for cylinder 2:
    • Change all spark plugs.
    • Unplug the connector:
      • 4-Cyl: Ignition discharge module (346).
      • V6: Ignition discharge module, Bank 2 (346F).
    • Turn the ignition switch to the ON position.
    • Connect Test Lamp (86 1 857) to:
      • 4-Cyl: pins 10 and 3 of the female connector.
      • V6: pins 10 and 1 of the female connector.
    • Activate: Ignition Coil Cyl 2.
    • Jiggle the leads and in-line connectors at several places and in different directions to reveal intermittent breaks and short circuits in the wiring harness. Observe the multimeter, test lamp or diagnostic tool while doing this.
    If the test lamp illuminates, go to step  6, otherwise go to next step.

  5. Rectifying the lead: The ignition trigger lead to the ignition discharge module is faulty. Rectify and go to step  11.
  6. Checking the ignition discharge module: Check visually that the rubber seals are intact, the contact springs are OK and the connector is free from corrosion and moisture. If the function is correct, go to next step, otherwise rectify the fault and go to step  11.
  7. Checking the ignition discharge module (continued):
    • Fit the test spark plug into the ignition discharge module.
    • Ground the spark plugs.
    • Position the ignition discharge module so that the spark plugs are inclined downward and the oil in the ignition coils covers the HT outputs.
    • Activate: Ignition Coil Cyl 2. Select automatic activation.
    • Check whether the relevant test spark plug produces a spark. If necessary, compare it by activating another ignition coil.
    If the function is correct, go to step  9, otherwise go to next step.
  8. Changing components: Change the ignition discharge module (V6 - Bank 2). When finished, go to step  11.
  9. Checking an injector: If the fuel injector is functioning properly, go to step  11, otherwise go to next step.
  10. Changing components: Change the faulty fuel injector. When finished, go to step  11.
  11. Checking misfiring:
    • Activate: Reset Misfire and Knock Counters.
    • Take a current reading with the diagnostic tool for all cylinders.
    • Drive the car with the same engine speed, air mass/combustion and coolant temperature as shown by Freeze Frame.
      NOTE: A few misfires in this load and engine speed range are acceptable.
    If any of the counters are incrementing continuously, the fault is still present. If all counters are remaining relatively stable, the fault has been rectified.
Fig 1: Cylinder Locations (4-Cyl)
G00207355Courtesy of SAAB-SCANIA OF AMERICA, INC.
Fig 2: Ignition Discharge Module Circuit (4-Cyl)
G00207356Courtesy of SAAB-SCANIA OF AMERICA, INC.
Fig 3: Cylinder Locations 2, 4 & 6 (V6)
G00207411Courtesy of SAAB-SCANIA OF AMERICA, INC.
Fig 4: Ignition Discharge Module Circuit (V6)
G00207412Courtesy of SAAB-SCANIA OF AMERICA, INC.
scientia non olet · About LEMON Manuals