DTC P1137: Front Oxygen Sensor (A/F) Circuit Range/Performance Problem
- Perform test procedure. See TESTING PROCEDURE . If DTC P1137 is only DTC set, go to next step. If any other DTCs exist, diagnose and repair those DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
- Start engine. Using a scan tool, observe engine coolant temperature as engine warms up. Warm engine until engine coolant temperature is above 158°F (70°C). If engine is already warmed up, allow engine to idle at specified idle speed for at least one minute. Using a scan tool, monitor front oxygen (A/F) sensor signal. If front (A/F) sensor signal is not more than 0.85 volt and equal to less than 1.15 volt at idle, go to step 4. If front (A/F) sensor signal is more than 0.85 volt and equal to less than 1.15 volt at idle, go to next step.
- Slowly accelerate engine (five seconds) from idle to 5,000 RPM and quickly release accelerator to decrease engine speed to idle a total of 5 times while using a scan tool to monitor front oxygen (A/F) sensor signal. If front oxygen (A/F) sensor signal is not more than 1.1 volt for a moment, go to next step. If front oxygen (A/F) sensor signal is more than 1.1 volt for a moment, go to step 6.
- Turn ignition off. Disconnect 30-pin ECM electrical harness connector B136 and 6-pin front oxygen (A/F) sensor electrical harness connector. Using a DVOM, measure resistance between harness side of specified terminals of ECM and front oxygen (A/F) sensor electrical harness connectors. See ECM-TO-FRONT OXYGEN SENSOR (A/F) TEST POINTS table. See Figure and Figure . If resistance is less than 5 ohms at all points, go to next step. If resistance is not less than 5 ohms at all points, locate and repair open circuit in wiring and check for poor terminal contact in all connectors between ECM and front oxygen (A/F) sensor. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
- Using a DVOM, measure resistance between specified terminals of 30-pin ECM electrical harness connector B136 and good chassis ground point. See ECM-TO-FRONT OXYGEN SENSOR (A/F) TEST POINTS table. See Figure. If resistance is more than one megohm, go to next step. If resistance is not more than one megohm, locate and repair short to ground in wiring between front oxygen (A/F) sensor and ECM. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .
- Check exhaust system for damage or loose components, poor front oxygen (A/F) sensor installation, exhaust system leaks ahead of front oxygen (A/F) sensor or loose front oxygen (A/F) sensor. Repair or replace exhaust system components as necessary. If exhaust system is okay, replace front oxygen (A/F) sensor. Clear memory. See CLEARING DIAGNOSTIC TROUBLE CODES . On Forester, Legacy and Outback models, validate repair by performing appropriate drive cycle. See DRIVE CYCLES . On Impreza and Outback Sport, perform verification procedure. See VERIFICATION PROCEDURE .