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P0157-O2 SENSOR 2/2 CIRCUIT LOW (CONTINUED) For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS). For a complete wiring diagram Refer to Section 8W. • When Monitored: • Set Condition: Possible Causes (K904) O2 RETURN DOWNSTREAM CIRCUIT SHORTED TO GROUND (K243) O2 2/2 SIGNAL CIRCUIT SHORTED TO GROUND (K243) O2 SIGNAL CIRCUIT SHORTED TO THE (K904) O2 RETURN DOWNSTREAM CIRCUIT (K243) O2 SIGNAL CIRCUIT SHORTED TO THE (Z992) O2 2/2 HEATER GROUND CIRCUIT O2 SENSOR PCM Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - Diagnostic Test 1. O2 SENSOR BELOW 2.52 VOLTS Start the engine. Allow the engine to reach normal operating temperature. With a scan tool, read the 2/2 O2 Sensor voltage. Is the voltage below 2.52 volts? Yes >> Go To 2 No >> Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 2. (K243) O2 2/2 SIGNAL CIRCUIT Turn the ignition off. Disconnect the 2/2 O2 Sensor harness connector. Ignition on, engine not running. With a scan tool, monitor the 2/2 O2 Sensor voltage. Is the O2 Sensor voltage above 4.8 volts? Yes >> Go To 3 No >> Go To 5 HB ENGINE ELECTRICAL DIAGNOSTICS 9 - 211 |