P0152

Circuit Description

The PCM supplies a bias voltage of about 450mV between the HO2S signal and low circuits. When measured with a 10 megohm digital voltmeter, this may display as low as 320 mV. The oxygen sensor varies the voltage within a range of about 1000 mV when the exhaust is rich, down through about 1000 mV when exhaust is lean. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If the Bank 2 HO2S 1 voltage remains excessively high for an extended period of time, DTC P0152 will be set

Conditions for Running the DTC

^ No Misfire, CKP, Fuel Injector, MAF, TP, EVAP, IAT, MAP, Fuel Trim, EGR or ECT DTCs are set.
^ Engine coolant temperature above 75°C (167°F).
^ Air fuel ratio is between 14.5 and 14.8 gps.
^ Throttle position is between 3% and 40%.

Conditions for Setting the DTC

^ Bank 2 HO2S 1 signal voltage remains above 975 mV during normal closed loop operation.
OR
^ Bank 2 HO2S 1 signal voltage remains above 200 mV during deceleration fuel mode operation.

Action Taken When the DTC Sets

^ The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
^ 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.

Diagnostic Aids

Check for the following conditions:

^ Fuel pressure high - An excessively rich fuel mixture can cause a DTC P0152 to be set. Refer to Fuel System Pressure Test. Fuel System Pressure Test
^ Fuel injector(s) faulty - Refer to Fuel Injector Balance Test. Component Tests and General Diagnostics
^ Check the EVAP Canister for Fuel Saturation. If the EVAP Canister is full of fuel, check canister control and hoses. Refer to EVAP Control System Diagnosis. Component Tests and General Diagnostics
^ Disconnect the MAF sensor and see if rich condition is corrected. If so, replace MAF sensor.
^ Check for a leaking fuel pressure regulator diaphragm by checking the vacuum line to the fuel pressure regulator for the presence of fuel.
^ An intermittent TP sensor output will cause the system to go rich, due to a false indication of the engine accelerating.
^ Shorted HO2S - If the HO2S is internally shorted the HO2S voltage displayed on the scan tool will be over 1 volt. Try disconnecting the affected HO2S and jumper the HO2S low circuit to ground with the key ON. If the displayed HO2S voltage changes from over 1000 mV to around 450mV, replace the HO2S. Silicon contamination of the HO2S can also cause a high HO2S voltage to be indicated. This condition is indicated by a powdery white deposit on the portion of the HO2S exposed to the exhaust stream. If contamination is evident, replace the affected HO2S.
^ Open HO2S Signal or Low Circuit or Faulty HO2S
- A poor connection or open in the HO2S signal or low circuit can cause the DTC to set during deceleration fuel mode. An HO2S which is faulty and not allowing a full voltage swing between the rich and lean thresholds can also cause this condition. Operate the vehicle while monitoring the HO2S voltage with a scan tool. If the HO2S voltage is limited within a range between 300 mv to 600 mv, check the HO2S signal and low circuit wiring and associated terminal connections. If the wiring and connections are OK, replace the HO2S.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

3. DTC P0152 failing during deceleration fuel mode operation may indicate a condition described in the Diagnostic Aids above. If the DTC P0152 test passes while the Fail Records conditions are being duplicated, an intermittent condition is indicated. Review the Fail Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.
7. 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.