For 1990-2009 cars
Engine Controls Components
HO2S Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### 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 Setting the DTC

• | No active transmission, TP sensor, EVAP system, misfire, IAT sensor, MAP sensor, fuel trim, fuel injector circuit, EVAP solenoid ODM, ECT sensor, or MAF sensor DTC(s) present.

• | 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.

• | Air/Fuel ratio is between 14.5 to 1 and 14.8 to 1.

• | Throttle position is between 3% and 40%.

• | Engine is running in closed loop

• | Engine Coolant Temperature greater than 75°C (167°F).

• | Above conditions must be present for a 100 second sample period.

• | Bank 2 H02S 1 lean to rich or rich to lean average transition response time was longer than 90 milliseconds.

• | Above conditions met for 5 seconds

### 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 Clear Information function or by disconnecting the PCM battery feed.

### 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:

1. 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.

2. 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 | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Engine at operating temperature.
2. Operate vehicle within parameters specified under Conditions for Setting the DTC criteria included in Diagnostic Support.
3. Monitor Bank 2 HO2S 1 voltage display on the scan tool HO2S data list

Does the HO2S voltage remain above the specified value?

800 mV

Go to Step 5

Go to Step 3

3 | Operate vehicle in Decel fuel mode (vehicle speed above 25 mph, TP angle below 3%) while monitoring HO2S 1 voltage display on the scan tool HO2S data list. Does the HO2S 1 voltage remain above the specified value while in Decel fuel mode? | 110 mV | Go to Step 5 | Go to Step 4
4 |

1. Turn ON the ignition switch.
2. Review and record scan tool Fail Records data.
3. Operate vehicle within Fail Records conditions as noted
4. Using a scan tool, monitor Specific DTC info for DTC P0132 until the DTC P0132 test runs

Does the scan tool indicate DTC P0132 failed this ignition?

--

Go to Step 5

Refer to Diagnostic Aids

5 | Disconnect HO2S 1 and jumper HO2S low circuit to ground. Does scan tool indicate HO2S 1 voltage near the specified value? | 450mV | Refer to Diagnostic Aids | Go to Step 6
6 |

1. Turn OFF the ignition switch.
2. Disconnect PCM connector
3. Turn ON the ignition switch.
4. Using a J 39200 Digital Multimeter, measure voltage between the HO2S 1 sensor signal at PCM harness connector and ground.

Does the Digital Multimeter indicate a voltage greater than specified value?

600 mV

Go to Step 7

Go to Step 8

7 | Repair short to voltage in the HO2S 1 signal circuit. Refer to Heated Oxygen Sensor (HO2S) Repair in Electrical Diagnosis. Is the action complete? | -- | Go to Step 9 | --
8 | Replace the PCM. Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 9 | --
9 |

1. Turn ON the ignition switch.
2. Review and record scan tool Fail Records data.
3. Clear DTCs
4. Operate vehicle within Fail Records conditions as noted.
5. Using a scan tool, monitor Specific DTC info for DTC P0152 until the DTC P0152 test runs

Does the scan tool indicate DTC P0152 failed this ignition?

--

Go to Step 2

System OK