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Home >> Saab >> 2001 >> 9-5 Base, 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Fault Code Diagnosis >> P1142: O2S Heater Circuit - Current Too High, Sensor 2 >> Fault Isolation Procedure

Fault Isolation Procedure

  1. Checking the preheating element power supply:
    • Unplug the connector: Heated oxygen sensor 2 (592Ra).
    • Turn the ignition switch to the ON position.
    • Contact ECM.
    • Connect Test Lamp (86 1 857) to pin 1 of the female connector and a good grounding point.
    • Activate: Fuel Pump Relay (Max 30 seconds).
    • 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  3, otherwise go to next step.
  2. Rectifying the lead: The lead from pin 2 (87) of the relay holder via fuse 15 to pin 1 of the female connector is faulty. Rectify the fault and go to step  6.
  3. Checking the preheating element power supply:
    • On 4-Cyl models, connect Test Lamp (86 1 857) to pins 1 and 2 of the female connector. On V6 models, Connect Test Lamp (86 1 857) to B+ and pin 2 of the female connector.
    • Activate: Preheating O2S 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  5, otherwise go to next step.
  4. Rectifying the lead: The lead from pin 2 (4-Cyl) or pin 49 (V6) of the control module to pin 2 of the female connector is faulty. Rectify the fault and go to step  6.
  5. Changing components: Change Heated oxygen sensor 2. When finished, go to next step.
  6. Final check:
    • Clear the DTCs in all systems.
    • Carry out a drive cycle: Drive the car at varying engine loads and engine RPM for 5 minutes.
    • Evaluate the drive cycle: Check that the DTC has not recurred.
    If the trouble code has recurred, the ECM is probably at fault and will need replacement. Replace with known-good ECM and retest. if no DTCs are present, then the steps taken to rectify the fault were correct.
Fig 1: O2S Heater Circuit (4-Cyl)
G00207373Courtesy of SAAB-SCANIA OF AMERICA, INC.
Fig 2: O2S Heater Circuit (V6)
G00207424Courtesy of SAAB-SCANIA OF AMERICA, INC.
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