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Home >> Saab >> 2002 >> 9-5 Linear, 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Fault Code Diagnosis >> P1491: EVAP Tank Pressure Sensor - Performance Problem & MALFUNCTIONAL Fuel Level Sensor >> Fault Isolation Procedure

Fault Isolation Procedure

  1. Checking the fault symptoms: If the customer has complained about the fuel gauge being faulty, go to next step. If trouble code P1451 is present, go to step  4.
  2. Checking the DTCs in MIU:
    • Contact MIU.
    • Obtain readouts of DTCs: Main instrument unit.
    If DTC B1720 has been stored, conduct fault diagnosis for trouble code B1720 (MIU), followed by diagnosis for DTC P1451 (ECM). If the trouble code is not present, go to next step.
  3. Checking the fuel level sensor: Carefully check the connector and connections to the fuel level sensor in the wiring harness. If no faults are found, replace the fuel level sensor. go to next step.
  4. Checking the sensor's power supply:
    • Turn the ignition switch to the ON position.
    • Unplug the connector: Pressure sensor, EVAP (585).
    • Take a voltage reading: 585:1 and B-.
    If the diagnostic tool shows 4.9-5.1 volts, go to step  6, otherwise go to next step.
  5. Rectifying the lead: The lead from crimped connection J21 to pin 1 of the female connector is faulty. Rectify the fault and go to step  12.
  6. Checking the sensor's grounding:
    • Take a voltage reading: 585:1 and 585:2.
    • 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 diagnostic tool shows 4.9-5.1 volts, go to step  8, otherwise go to next step.
  7. Rectifying the lead: The lead from crimped connection J22 to pin 2 of the female connector is faulty. Rectify the fault and go to step  12.
  8. Checking the control module's sensor input:
    • Contact ECM.
    • Read value: Fuel Tank Pressure.
    If the diagnostic tool shows 2.5 kPa, go to next step, otherwise go to step  10.
  9. Checking the control module's sensor input (continued):
    • Connect a jumper lead between pins 2 and 3 of the female connector.
    • Read value: Fuel Tank Pressure.
    If the diagnostic tool shows -2.5 kPa, go to step  11, otherwise go to next step.
  10. Rectifying the lead: The lead from pin 3 of the female connector to pin 59 of the control module is faulty. Rectify the fault and go to step  12.
  11. Changing components: Change Pressure sensor, EVAP. When finished, go to step 12.
    12. NOTE: Do not touch the brake pedal.
  12. Initiating diagnostics:
    • Check the diagnostic status of the trouble code with the diagnostic tool.
    • Start the engine and run it at idling speed.
    • Let the engine run at idling speed until the coolant temperature exceeds 60°C and for at least 4 minutes.
    • State what the diagnostic tool shows:
      • OK - The steps taken to rectify the fault were correct. Clear the DTCs in all systems.
      • NOT READY - The diagnosis has not yet been performed or has been cancelled. If the diagnosis has been cancelled, it can be restarted if the car is rolled a few meters and then stopped with the handbrake.
      • DTC - Diagnosis indicates that the fault is still present.
Fig 1: ECM To Main Instrument Unit Circuit
G00207383Courtesy of SAAB-SCANIA OF AMERICA, INC.
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