Fault Isolation Procedure
- Checking the sensor's grounding:
- Unplug the connector: Coolant temperature sensor (202).
- Connect Test Lamp (86 1 857) to B+ and pin 2 of the female connector (black).
- 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.
- Rectifying the lead: The lead from crimp connection 17 (black) to pin 2 of the female connector is faulty. Rectify the fault and go to step 7.
- Checking the control module's sensor input:
- Turn the ignition switch to the ON position.
- Read value: Coolant Temperature.
If the reading shows -40°C, go to step 5, otherwise go to next step.
- Rectifying the lead: The lead from pin 1 (white/green) of the female connector to pin 39 of the control module is faulty. Rectify the fault and go to step 7.
- Checking the control module's sensor input (continued):
- Connect a jumper lead between pins 1 and 2 of the female connector.
- Read value: Coolant Temperature.
If the reading shows 160°C, go to next step, otherwise go to step 4.
- Changing components: Change the coolant temperature sensor. When finished, go to next step.
- 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.
Courtesy of SAAB-SCANIA OF AMERICA, INC.
Courtesy of SAAB-SCANIA OF AMERICA, INC.