Circuit Description
The powertrain control module (PCM) supplies a bias voltage of approximately 450 mV between the heated oxygen sensor (HO2S) signal and the low circuits. When measured with a 10 megaohm digital voltmeter (DVM), this may display as low as 350 mV. The oxygen sensor varies the voltage from approximately 1000 mV when the exhaust is rich, to approximately 100 mV when exhaust is lean. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing the injector pulse width as necessary. If the HO2S 1 voltage remains excessively low for an extended time, DTC P0131 will set.
Conditions for Running the DTC
| • | DTC P0101, DTC P0102, DTC P0103, DTC P0106, DTC P0107, DTC P0108, DTC P0112, DTC P0113, DTC P0117, DTC P0118, DTC P0121, DTC P0122, DTC P0123, DTC P0125, DTC P0128, DTC P0201, DTC P0202, DTC P0203, DTC P0204, DTC P0205, DTC P0206, DTC P0410, DTC P0440, DTC P0442, DTC P0443, DTC P0446, DTC P0449, DTC P1141 are not set. |
| • | The system voltage is more than 9 volts. |
| • | The Closed Loop commanded air-to-fuel ratio is between 12 and 16.5. |
| • | The throttle angle is between 3 percent and 35 percent . |
Conditions for Setting the DTC
The HO2S 1 signal voltage remains below 175 mV during normal Closed Loop operation.
OR
The HO2S 1 signal voltage remains below 600 mV during Power Enrichment Mode fuel control operation.
Either of the above conditions is present for up to 50 seconds.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Freeze Frame/Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns the MIL OFF after three consecutive trips in which the diagnostic runs and passes. |
| • | A last test failed, or the current DTC, clears when the diagnostic runs and passes. |
| • | A History DTC clears after 40 consecutive warm-up cycles, if no other emission related diagnostic failures are reported. |
| • | Use a scan tool in order to clear the MIL diagnostic trouble code. |
| • | Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module Description , Clearing Diagnostic Trouble Codes. |
Diagnostic Aids
Notice: Use the connector test adapter kit J 35616-A for any test that
requires probing the following items:
• The PCM harness connectors • The electrical center fuse/relay cavities • The component terminals • The component harness connector
Check for the following conditions.
| • | Incorrectly routed heated oxygen sensor wiring |
| The sensor pigtail may be routed incorrectly and contacting the exhaust system. |
| • | Faulty PCM to engine block grounds |
| Refer to Ground Distribution Schematics in Wiring Systems. |
| • | Fuel pressure that is too low |
| The system will go lean if pressure is too low. The PCM can compensate for some decrease. However, if fuel pressure is too low, DTC P0131 may be set. Refer to DTC P0131 . |
| • | Problems with the fuel injectors |
| Refer to Fuel Injector Solenoid Coil Test . |
| • | Vacuum leaks |
| Check for the following conditions: |
| - | Disconnected or damaged vacuum hoses. Refer to Emission Hose Routing Diagram |
| - | An incorrectly installed or malfunctioning crankcase ventilation valve. |
| - | Leaks at the throttle body, the EGR valve, and the intake manifold mounting surfaces. |
| • | Exhaust leaks |
| An exhaust leak may cause outside air to be pulled into the exhaust gas stream past the HO2S, causing the system to appear lean. Check for exhaust leaks that may be producing a false lean condition. |
| • | Fuel contamination |
| Even small amounts of water in the fuel injectors can cause a lean exhaust to be indicated. Excessive alcohol in the fuel can also cause this condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
If none of the above conditions are present, replace the affected HO2S. Refer to Heated Oxygen Sensor 1 Replacement or Heated Oxygen Sensor 2 Replacement .
If the condition is intermittent, refer to Intermittent Conditions .
Test Description
The number below refer to step number on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||||||||||||||
2 |
Is the HO2S voltage less than the value specified? | 86 mV | Go to Step 4 | Go to Step 3 | ||||||||||||||||||||
The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
Repair any of the above or similar engine conditions as necessary. Was a condition found and repaired? | -- | Go to Step 10 | Go to Diagnostic Aids | |||||||||||||||||||||
4 |
Is the HO2S voltage within the specified value range? | 351-551 mV | Go to Step 5 | Go to Step 6 | ||||||||||||||||||||
5 | The HO2S may be detecting a lean exhaust condition. Check for one of the following conditions:
Repair any of the above or similar engine conditions as necessary. Was a condition found and repaired? | -- | Go to Step 10 | Go to Step 8 | ||||||||||||||||||||
6 |
Is the infinite resistance measured on both tests? | -- | Go to Step 9 | Go to Step 7 | ||||||||||||||||||||
7 | Repair the HO2S high signal circuit shorted to ground or shorted to the HO2S low reference circuit . Refer to Wiring Repairs in Wiring Systems. In the action complete? | -- | Go to Step 10 | -- | ||||||||||||||||||||
8 | Replace the HO2S. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||||||||||||||||
9 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||||||||||||||||
10 |
Does the scan tool indicate that this test Ran and Passed? | -- | Go to Step 11 | Go to Step 2 | ||||||||||||||||||||
11 | Review Captured Info using the scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to the Diagnostic Trouble Code (DTC) List | System OK | ||||||||||||||||||||
