Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2004 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

DTC P0131

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check-Engine Controls?	-	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Start the engine. Allow the engine to idle at operating temperature. Refer to Scan Tool Data List . Clear the DTC and record the Freeze/Frame Failure Records. Observe the HO2S 1 parameter with a scan tool. Is the voltage less than the specified value?	78 mV	Go to Step 4	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	-	Go to Step 4	Go to Intermittent Conditions
4	Turn OFF the ignition. Disconnect the heated oxygen sensor (HO2S) 1 connector. Turn ON the ignition, with the engine OFF. Observe the HO2S 1 parameter with a scan tool. Is the voltage less than the specified value?	78 mV	Go to Step 5	Go to Step 6
5	Test the HO2S 1 high signal circuit for a short to ground or a short to the HO2S 1 low signal circuit. Refer to Circuit Testing , Wiring Repairs , andHeated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 11	Go to Step 8
6	Inspect for the following conditions that may affect the HO2S operation: NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. HO2S contamination NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring Exhaust system leaks or restrictions Evaporative emissions (EVAP) system malfunction-Inspect the EVAP control system. Refer to Inspection/Maintenance (I/M) Evaporative Emission (EVAP) System Set Procedure . The fuel pressure-Incorrect fuel pressure can affect HO2S operation. Refer to Fuel System Diagnosis . Did you find and correct the condition?	-	Go to Step 11	Go to Step 7
7	Test for an intermittent and for a poor connection at the harness connector of the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 11	Go to Step 9
8	Test for shorted terminals and for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 11	Go to Step 10
9	Replace the HO2S 1. Refer to Heated Oxygen Sensor Replacement - Position 1 . Did you complete the replacement?	-	Go to Step 11	-
10	Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement . Did you complete the replacement?	-	Go to Step 11	-
11	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	-	Go to Step 2	Go to Step 12
12	Observe the Capture Info with a scan tool. Are there any DTCs that have not diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List	System OK