Circuit Description
The Heated Oxygen sensor (HO2S) is a sensor used in order to detect the oxygen content in the exhaust. The powertrain control 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.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0201-P0208, P0410, P0440, P0442, P0443, P0446, P0449, P1415, P1416, or P1441 are not set. |
| • | The throttle position 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 and 14.90. |
| • | The conditions above met for 3 seconds. |
| • | The AIR diagnostic test is not active. |
| • | The EGR flow diagnostic test is not active. |
| • | The catalyst diagnostic is not active. |
Conditions for Setting the DTC
The HO2S bank 1 sensor 1 signal voltage remains above 900 mV for approximately 50 seconds during normal Closed Loop fuel control.
OR
The HO2S bank 1 sensor 1 signal voltage remains above 200 mV during deceleration fuel control.
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. |
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.
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 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 the a rich condition. The PCM will compensate for some increase. However, if the fuel pressure is too high, DTC P0132 may set. |
| • | The fuel injectors--If the fuel injectors deliver improper fuel volume at the specified pressure, DTC P0132 may set. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 . |
| • | The EVAP canister--Check the EVAP canister and 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 exposed to the exhaust stream. |
If none of the above conditions are present, replace the 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 fail records data. If both banks were rich, check for a condition that can cause a rich engine operation. If only the rear bank was rich, the rich condition, such as an intermittent open HO2S ground circuit or an intermittent short to voltage on the signal circuit, is isolated to that bank.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies whether or not the HO2S voltage is switching from below 300 mV to above 600 mV, or is remaining above 600 mV.
-
This step verifies the bias voltage from the PCM and the condition of the circuit wiring. With the sensor disconnected, the scan tool should display a bias voltage near 450 mV.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Does voltage measure more than the specified value? | 600 mV | Go to Step 4 | Go to Step 3 | |
3 |
Does the scan tool indicate that DTC P0132 failed this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids |
Does the scan tool indicate that the HO2S bank 1 sensor 1 voltage is near the specified value? | 450 mV | Go to Diagnostic Aids | Go to Step 5 | |
5 |
Was a problem found? | -- | Go to Step 7 | Go to Step 6 |
6 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 7 | -- |
7 |
Does the DTC run and pass? | -- | Go to Step 8 | Go to Step 2 |
8 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
