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 320mV. The oxygen sensor varies the voltage within a range of about 1000mV when the exhaust is rich, down through about 10mV 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. |
| • | Throttle position is between 3% and 40%. |
Conditions for Setting the DTC
| • | Bank 2 H02S 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 malfunction indicator lamp (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 Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL 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 Refer to Fuel System Pressure Test . |
| • | Fuel injector(s) faulty - Refer to Fuel Injector Balance Test . |
| • | Check the EVAP Canister for Fuel Saturation. If the EVAP Canister is full of fuel, check canister control and hoses. Refer to Evaporative Emission Control System Diagnosis . |
| • | Disconnect the MAF sensor and see if rich condition is corrected. If so, replace MAF sensor. Refer to Mass Airflow Sensor Replacement . |
| • | 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 1000mV 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 300mV to 600mV, 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:
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This DTC failing during deceleration fuel mode operation may indicate a condition described in the Diagnostic Aids above. If the DTC 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.
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This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM isreplaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 |
Does the HO2S voltage remain above the specified value? | 800 mV | ||
Operate vehicle in Decel fuel mode (vehicle speed above 25 mph, TP angle below 3%) while observing the HO2S voltage parameter on the scan tool. Does the HO2S voltage remain more thanthe specified value while in Decel fuel mode? | 110 mV | |||
4 |
Does the scan tool indicate this DTC failed this ignition? | -- | Go to Diagnostic Aids | |
5 | Disconnect the HO2 S and jumper the low circuit to a good ground. Does scan tool indicate HO2S voltage near the specified value? | 450mV | Go to Diagnostic Aids | |
6 |
Does the voltage measure more thanspecified value? | 600 mV | ||
Repair the short to voltage in the HO2S signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | -- | ||
8 |
Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | -- | |
9 |
Does the DTC reset? | -- | System OK |
