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--has more oxygen--the sensor produces a low voltage signal. When the exhaust stream is rich--has 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 1 remains at or near the bias voltage for a calibrated period of time, DTC P0134 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 inactive |
| • | AIR diagnostic test--if equipped--inactive |
| • | Catalyst diagnostic test inactive |
| • | System voltage between 9-18 volts |
| • | Engine running for 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 1 signal voltage remain within 400 and 500 mV for approximately 57 seconds.
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
If the condition is intermittent, refer to Intermittent Conditions in Symptoms.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Check the HO2S bank 1 sensor 1 wiring, the PCMs response. With the harness connector terminals jumpered together, the scan tool should display an HO2S bank 1 sensor 1 voltage below 75 mV.
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This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read only memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||||||||
2 | Are any DTCs set other than DTC P0134? | -- | ||||||||
3 |
Does the scan tool indicate HO2S bank 1 sensor 1 voltage varying outside the specified values? | 400-500 mV | ||||||||
4 |
Does the scan tool indicate DTC P0134 failed last test? | -- | Go to Diagnostic Aids | |||||||
Does the scan tool indicate an HO2S bank 1 sensor 1 voltage below the specified value? | 75 mV | |||||||||
6 |
Did you find and correct the condition? | -- | ||||||||
7 |
Did you find and correct the condition? | -- | ||||||||
8 | Replace HO2S bank 1 sensor 1. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 . Is the action complete? | -- | -- | |||||||
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||||
10 |
Does the scan tool indicate DTC P0134 passed? | -- | System OK |
