Circuit Description
The HO2S is a sensor used to detect oxygen-content in the exhaust. The 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. If HO2S bank 1 sensor 2 remains too low for a calibrated period of time, DTC P0137 will set.
Conditions for Running the DTC
| • | MAF, TP, EVAP, IAT, MAP, AIR (if equipped), ECT, or Injector DTCs are not set |
| • | EGR flow diagnostic test inactive |
| • | AIR (if equipped) diagnostic test inactive |
| • | Catalyst diagnostic test inactive |
| • | System voltage between 9 and 18 volts |
| • | Engine running more than 200 seconds |
| • | Change in TP angle more than 5 percent occurs at least 4 times |
Conditions for Setting the DTC
HO2S bank 1 sensor 2 signal voltage remains between 400mV (0.4 Volts) and 500mV (0.5 Volts) for approximately 57 seconds during normal closed loop fuel control.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test runs and fails. |
| • | The PCM stores the conditions present when the DTC set as Freeze Frame/Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after the third consecutive trip in which the diagnostic runs and passes. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear DTC Information function. |
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.
For intermittent conditions, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Verifies whether or not the HO2S sensor voltage is switching from below 300 mV to above 500 mV, or remaining below 300 mV.
-
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 |
|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||
Does voltage remain below the value specified? | 9 mV | |||
3 |
Does the scan tool indicate that DTC P0137 failed last test? | -- | Go to Diagnostic Aids | |
Does the scan tool display an HO2S bank 1 sensor 2 voltage near the specified value? | 450 mV | |||
5 |
Did you find and correct the condition? | -- | ||
6 | Replace HO2S bank 1 sensor 2. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 . Is the action complete? | -- | -- | |
7 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | -- | |
8 |
Does the scan tool indicate that DTC P0137 passed? | -- | System OK |
