DTC P0137: Secondary HO2S (Sensor 2) Circuit Low Voltage Reset the ECM/PCM (see page 11-4). Start the engine. Hold the engine at 3,000 rpm (min-1) with no load (in Park or neutral) until the radiator fan comes on. Check the secondary HO2S (Sensor 2) output voltage at 3,000 rpm (min-1) with the scan tool. Does the voltage stay at 0.3 V or less? YES - Go to step 4. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the secondary HO2S (Sensor 2) and at the ECM/PCM. Turn the ignition switch OFF. Disconnect the secondary HO2S (Sensor 2) 4P connector. Turn the ignition switch ON (II). Check the secondary HO2S (Sensor 2) output voltage with the scan tool. Does the voltage stay at 0.3 V or less? YES - Go to step 8. NO - Replace the secondary HO2S (Sensor 2). Turn the ignition switch OFF. Disconnect ECM/PCM connector E (31P).

Check for continuity between the secondary HO2S (Sensor 2) 4P connector terminal No. 2 and body ground. SECONDARY HO2S (SENSOR 2) 4P CONNECTOR Terminal side of male terminals Is there continuity? YES - Repair short in the wire between the ECM/PCM (E2) and the secondary HO2S (Sensor 2). NO - Substitute a known-good ECM/PCM and recheck (see page 11-6). If symptom/indication goes away, replace the original ECM/PCM.