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. If HO2S bank 2 sensor 1 remains too high for a calibrated period of time, DTC P0152 will set.
Conditions for Running the DTC
| • | No TP sensor, MAF sensor, MAP sensor, IAT sensor, ECT sensor, EVAP system, AIR system (if equipped), or fuel injector DTCs are set. |
| • | TP angle is between 3-25 percent. |
| • | System voltage is between 9-18 volts. |
| • | AIR System tests inactive |
| • | EGR Flow test inactive |
| • | Closed loop fuel control is enabled |
| • | Air fuel ratio is between 14.4-14.9 |
| • | Conditions above met for 3 seconds. |
Conditions for Setting the DTC
| • | HO2S bank 2 sensor 1 signal voltage remains above 900 mV (0.9 V) for approximately 95 seconds during normal closed loop fuel control. |
| OR |
| • | HO2S bank 2 sensor 1 signal voltage remains above 200 mV (0.2 V) for approximately 11 seconds during deceleration 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
Check the following items:
| • | HO2S wire routing |
| • | Fuel pressure, refer to Fuel System Pressure Test . |
| 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 P0152 may set. |
| • | Fuel injectors -- If the fuel injectors deliver improper fuel volume at the specified pressure, DTC P0152 may set. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 . |
| • | EVAP canister -- Check the EVAP canister and hoses for fuel saturation. |
| • | Silicon contamination -- Silicon contamination of the HO2S sensor 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. |
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 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 in Symptoms.
If none of the above conditions are present, replace the bank 2 sensor sensor. Refer to Heated Oxygen Sensor Replacement - Bank 2 .
Important: If the sensor appears contaminated, correct the source of the oxygen
sensor contamination before replacing the sensor in order to prevent future
contamination. Typical contamination sources include the following:
• Fuel contamination, refer to
Alcohol/Contaminants-in-Fuel Diagnosis
. • Use of improper RTV sealant • Engine oil or engine coolant consumption, refer to
Oil Consumption Diagnosis
in Engine Mechanical.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Verifies whether or not the HO2S sensor voltage is switching properly.
-
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 above the value specified? | 900 mV | |||
3 |
Does the scan tool indicate that DTC P0152 failed last test? | -- | Go to Diagnostic Aids | |
Does the scan tool display an HO2S bank 2 sensor 1 voltage near the specified value? | 450 mV | Go to Diagnostic Aids | ||
5 |
Did you find and correct the condition? | -- | ||
6 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
7 |
Does the scan tool indicate that DTC P0152 passed? | -- | System OK |
