Circuit Description
The heated oxygen sensor (HO2S) is a sensor used to detect oxygen content in the exhaust. The powertrain control module (PCM) supplies the sensor with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The sensor varies the voltage based on the oxygen content in the exhaust. When the exhaust stream is lean (more oxygen), the sensor produces a low voltage signal. When the exhaust stream is rich (less oxygen), the sensor produces a high voltage signal. The PCM monitors the HO2S signal during Closed Loop. To correct for rich or lean conditions, the PCM adjusts the injector pulse width. This DTC indicates that the HO2S voltage remained too high for a calibrated period of time.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0201-P0208, P0410, P0412, P0418, P0419, P0440, P0442, P0443, P0446, P0449, P1415, P1416, or P1441 are not set. |
| • | The throttle position (TP) angle is between 3-25 percent. |
| • | The system voltage is between 9-18 volts. |
| • | The Closed Loop fuel control is enabled. |
| • | The air/fuel ratio is between 14:40-14:90. |
| • | The secondary air injection (AIR) diagnostic test is not active. |
| • | The exhaust gas recirculation (EGR) flow diagnostic test is not active. |
| • | The catalyst diagnostic is not active. |
| • | All conditions above met for 3 seconds. |
Conditions for Setting the DTC
| • | The HO2S signal voltage remains above 900 mV (0.9 V) for approximately 3 seconds during normal Closed Loop fuel control. |
| or |
| • | The HO2S signal voltage remains above 200 mV (0.2 V) during deceleration fuel cut-off (DFCO) control. |
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. |
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. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
Notice: Do not solder heated oxygen sensor wires. Soldering the wires will result in the loss of the air reference to the sensor. Refer to Engine Electrical for proper wire and connection repair techniques.
Check the following items:
| • | The HO2S wire routing--The sensor wiring may be routed incorrectly and contacting the exhaust system. |
| • | The fuel pressure--Fuel pressure that is too high will cause a rich condition. The PCM will compensate for some increase. However, if the fuel pressure is too high, the DTC may set. |
| • | The fuel injectors--If the fuel injectors deliver improper fuel volume at the specified pressure, the DTC may set. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 . |
| • | The evaporative emission (EVAP) canister--Check the EVAP canister and the hoses for fuel saturation. |
| • | Silicon contamination--Silicon contamination of the HO2S can also cause a high HO2S signal voltage. This condition is indicated by a powdery white deposit on the portion of the HO2S that is exposed to the exhaust stream. |
If none of the above conditions are present, replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 and Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 .
Review the front and rear long term fuel trim values on the scan tool Failure Records data. If both banks were rich, check for a condition that would cause a rich engine operation. If only the rear bank was rich, the rich condition is isolated to that bank, such as an intermittent open HO2S ground circuit or an intermittent short to voltage on the signal circuit.
If the condition is intermittent, refer to Intermittent Conditions .
Test Description
The number below refer to the 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 |
Does voltage remain above the value specified? | 900 mV | Go to Step 4 | Go to Step 3 |
3 |
Does the scan tool indicate that this DTC passed? | -- | Go to Intermittent Conditions | Go to Step 4 |
Does the scan tool display an HO2S voltage near the specified value? | 450 mV | Go to Diagnostic Aids | Go to Step 5 | |
5 | Test for a short between the HO2S bank 1 sensor 1 high signal circuit and a PCM 5-volt or 12-volt reference circuit. Refer to Engine Controls Schematics . Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 |
6 | Inspect for poor connections at the PCM harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 |
7 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC run and pass? | -- | Go to Step 9 | Go to Step 2 |
9 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
