P0131
DTC P0131 or P0151
Circuit Description
The powertrain control module (PCM) supplies a voltage of about 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The oxygen sensor (02) varies the voltage from approximately 1 ,000 mVwhen the exhaust is rich, through approximately 10 mV when the exhaust is lean.
The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period, and determines if the majority of the samples are out of the operating range.
The PCM monitors the HO2S voltage for being fixed below a predetermined voltage. If the PCM detects the voltage is below a predetermined voltage, a DTC sets.
DTC Descriptors
This diagnostic procedure supports the following DTCs.
- DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1
- DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1
Conditions for Running the DTC
- DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121. P0122, P0123, P0125, P0128, P0200, P0300, P0443, P0496, P111 1, P1112, P1114, P1115, P1121. or P1122 are not set.
- The ignition 1 voltage is between 10-18 volts.
- The fuel level is more than 10 percent.
- The loop status is CLOSED.
- Intrusive tests are not in progress.
- DTC P0131 and P0151 run continuously when the above conditions are met.
Lean Test Enable
- The air fuel ratio is between 14.5:1 and 14.7:1.
- The throttle position (TP) is between 3-70 percent.
- The above conditions are met for at least 2 seconds.
Power Enrichment Test Enable
- Power enrichment is active for at least 1 second.
- The engine has been running for at least 30 seconds.
Conditions for Setting the DTC
Lean Test
The HO2S voltage is less than 200 mV for 165 seconds.
Power Enrichment Test
The HO2S voltage is less than 360 mV for 10 seconds.
Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
- The control module commands Open Loop.
Conditions for Clearing the MIL/DTC
- 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.
9 Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Important:
- Before you service the PCM, remove any debris from the PCM connector surfaces. Inspect the PCM connector gaskets when you diagnose or replace the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
- For any test that requires probing the PCM or component harness connectors, use the J 35616-B Connector Test Adapter Kit. Using this kit prevents any damage to the harness connector terminals.
The PCM sets this DTC when the vehicle runs out of fuel. Inspect for the following conditions:
- The heated oxygen sensor (HO2S) wires. The sensor pigtail may be in contact with the exhaust manifold or the exhaust system.
- The oxygen supply. An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provide the supply of oxygen. Inspect the HO2S wires and connections for breaks or for contamination.
- An intermittent ground. Inspect for an intermittent ground in the signal wire between the connector and the sensor.
- Lean injectors-Perform the Injector Balance Test.
- Fuel contamination-Water near the in-tank fuel pump inlet can be delivered to the injectors. The water causes a lean exhaust and can set a DTC.
- The fuel pressure-If the fuel pressure is too low, the system will be lean.
- Exhaust leaks-An exhaust leak near the HO2S can cause a lean condition.
- Vacuum or crankcase leaks can cause a lean condition.
It the above components are OK, the HO2S may be at fault.
Test Description
DTC P0131 or P0151 Steps 1-4:
DTC P0131 or P0151 Steps 5-13:
The numbers below refer to the step numbers on the diagnostic table.
2. If the voltage is below the specified value, the condition is present.
4. A disconnected sensor should indicate a bias voltage. If the voltage is low, inspect the signal circuit for a short to ground.