| DTC P0131 (1-1): | Primary HO2S(Sensor 1) Circuit Low Voltage |
| 1. | Reset the ECM/PCM. |
| 2. | 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. |
| 3. | Check the primary HO2S (Sensor 1) output voltage with the HDS or the scan tool during acceleration using wide open throttle. Is there 0.5 V or less? YES - Go to 4. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the primary HO2S (Sensor 1) and at the ECM/ PCM.n |
| 4. | Check the fuel pressure. Is it normal? YES - Go to 5. NO - Repair the fuel supply system.n |
| 5. | Turn the ignition switch OFF. |
| 6. | Disconnect the primary HO2S (Sensor 1) 4P connector. |
| 7. | Turn the ignition switch ON (II). |
| 8. | Check the primary HO2S (Sensor 1) output voltage with the HDS or the scan tool. Is there 0.5 V or less? YES - Go to 9. NO - Replace the primary HO2S (Sensor 1).n |
| 9. | Turn the ignition switch OFF. |
| 10. | Disconnect ECM/PCM connector A (31P). |
| 11. | Check for continuity between the primary HO2S (Sensor 1) 4P connector terminal No. 1 and body ground.
Is there continuity? YES - Repair short in the wire between the ECM/PCM (A6) and the primary HO2S (Sensor 1).n NO - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/ PCM.n |