For 1990-2009 cars

Refer to

#### HO2S Sensors

Engine Controls Components
Information Sensors
Cruise Control, VSS
MAF Sensor, EVAP System, EGR Valve
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
.

### Circuit Description

The PCM supplies a bias voltage of about 450 mV 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 10 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 at or near the 450 mV bias for an extended period of time, DTC P0154 will be set, indicating an open sensor signal or sensor low circuit.

### Conditions for Setting the DTC

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

• | Engine run time longer than 200 seconds.

• | Bank 2 HO2S 1 signal voltage remains between 400 mV and 500 mV for longer than 10 seconds.

### 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:

• | Poor connection or damaged harness - Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

• | Faulty HO2S heater or heater circuit - With the ignition ON the HO2S voltage displayed on a scan tool should gradually drop to below 250 mV or rise to above 600 mV. If not, disconnect the HO2S and connect a test light between the HO2S ignition feed and heater ground circuits. If the test light does not light, repair the open ignition feed or sensor ground circuit as necessary (refer to Heated Oxygen Sensor (O2S) Repair in Repair Procedures Electrical Diagnosis section 8A-5). If the test light lights and the HO2S signal and low circuits are OK, replace the HO2S.

• | Intermittent test - With the ignition ON, monitor the HO2S signal voltage while moving the wiring harness and related connectors. If the fault is induced, the HO2S signal voltage will change. This may help isolate the location of the malfunction.

### Test Description

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

1. If the DTC P0154 test passes while the Fail Records conditions are being duplicated, an intermittent condition is indicated. Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

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. Install scan tool
2. Engine at operating temperature
3. Operate engine above 1200 RPM for two minutes.

Does the scan tool indicate Bank 2 HO2S 1 voltage varying outside the specified values?

400-500 mV

Go to Step 3

Go to Step 4

3 |

1. Turn ON the ignition switch.
2. Review and record scan tool Fail Records data and note parameters.
3. Operate vehicle within Fail Records conditions as noted.
4. Using a scan tool, monitor Specific DTC info for DTC P0154 until the DTC P0154 test runs.
5. Note test result.

Does the scan tool indicate DTC P0154 failed this ignition?

--

Go to Step 4

Refer to Diagnostic Aids

4 |

1. Turn ON the ignition switch.
2. Disconnect Bank 2 HO2S 1.
3. Jumper the HO2S high and low signal circuits (PCM side) to ground.
4. Using a scan tool, monitor Bank 2 HO2S 1 voltage.

Is Bank 2 HO2S 1 voltage below the specified value?

150 mV

Go to Step 8

Go to Step 5

5 |

1. Remove jumper wire
2. Using a J 39200 Digital Multimeter, measure voltage between the Bank 2 HO2S 1 signal circuit (PCM side) and the Bank 2 HO2S 1 heater ground circuit

Does Bank 2 HO2S 1 voltage measure near the specified value?

450 mV

Go to Step 6

Go to Step 7

6 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Check continuity of the Bank 2 HO2S 1 low circuit.
4. If the Bank 2 HO2S 1 low circuit measures over 5 ohms, repair open or poor connection as necessary. Refer to Heated Oxygen Sensor (HO2S) Repair in Electrical Diagnosis.

Was a Bank 2 HO2S 1 low circuit problem found and corrected?

--

Go to Step 13

Go to Step 9

7 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM
3. Check continuity of the Bank 2 HO2S 1 signal circuit.
4. If the Bank 1 HO2S 2 signal circuit measures over 5 ohms, repair open or poor connection as necessary. Refer to Wiring Repairs in Electrical Diagnosis.

Was a Bank 2 HO2S 1 signal circuit problem found and corrected?

--

Go to Step 13

Go to Step 10

8 | Check for a poor Bank 2 HO2S 1 signal or low circuit terminal connection at the Bank 2 HO2S 1 harness connector and replace terminal(s) if necessary. Refer to Heated Oxygen Sensor (HO2S) Repair in Electrical Diagnosis. Did any terminals require replacement? | -- | Go to Step 13 | Go to Step 11
9 | Check for poor Bank 2 HO2S 1 low circuit terminal connection at the PCM and replace terminal if necessary. Refer to Wiring Repairs in Electrical Diagnosis. Did the terminal require replacement? | -- | Go to Step 13 | Go to Step 12
10 | Check for poor Bank 2 HO2S 1 signal circuit terminal connection at the PCM and replace terminal if necessary. Refer to Wiring Repairs in Electrical Diagnosis. Did the terminal require replacement? | -- | Go to Step 13 | Go to Step 12
11 | Replace Bank 2 HO2S 1. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | Go to Step 13 | --
12 | Replace the PCM. Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 13 | --
13 |

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 P0154 until the DTC P0154 test runs.

Does scan tool indicate DTC failed this ignition?

--

Go to Step 2

System OK