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

### Circuit Description

The PCM continuously monitors the Heated Oxygen Sensor (HO2S) activity for 100 seconds. During the monitor period the PCM counts the number of times that the HO2S responds from rich to lean and from lean to rich and adds the amount of time it took to complete all transitions. With this information, an average time for all transitions can be determined. The PCM then divides the rich to lean average by the lean to rich average to obtain a ratio. A DTC P1154 sets if the HO2S ratio is not within range.

### Conditions for Running the DTC

• | DTCs P0102, P0103, P0112, P0113, P0117, P0118, P0125, P0335, P0336, P0351-P0358, P1120, P1220, P1221, P1258 not set.

• | The fuel system is operating in Closed Loop.

• | The engine run time is greater than 2.0 seconds.

• | The engine speed is greater than 1000 RPM but less than 2300 RPM.

• | The ignition voltage is greater than 9.0 volts.

• | The engine coolant temperature is greater than 65°C (149°F).

• | The MAF is between 15 g/s and 35 g/s.

• | The EVAP purge duty cycle is greater than 0%.

### Conditions for Setting the DTC

The PCM determines that the HO2S transition time ratio is not at the expected value.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A last test failed, or current DTC, clears when the diagnostic runs and does not fail.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Use a scan tool in order to clear the MIL and the DTC.

### Diagnostic Aids

• | Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.

• | An oxygen supply inside the HO2S is necessary for proper operation. This supply of oxygen is provided through the HO2S wires. All HO2S wires and connections should be inspected for breaks or contamination. Refer to Heated Oxygen Sensor Wiring Repairs In Wiring Systems.

For an intermittent, refer to Symptoms .

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step determines if the fault is present. This test may take 5 minutes for the diagnostic to run. For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616 . Using this kit will prevent damage to the harness connector terminals.

2. When DTCs P1134 and P1154 are set at the same time, is good indication that a fuel contamination condition is present.

3. An exhaust leak 6 to 12 inches away from the HO2S can cause a DTC to set.

4. This step tests whether a good ground circuit is available.

5. This step tests the integrity of the signal circuit to the PCM.

6. Certain RTV silicone gasket materials give off vapors that can contaminate the HO2S. There is also a possibility of silicone contamination caused by silicone in the fuel. If the sensors appear contaminated by silicone and all the silicone sealant is a non-silicone base, advise the customer to try a different fuel company. A missing fuel filler restrictor, indicates the customer may have used leaded fuel.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Important: If any DTCs are set (Except P1134), refer to those DTCs before proceeding with this diagnostic table.

1. Install a scan tool.
2. Idle the engine at the normal operating temperature.
3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.
4. Monitor the Diagnostic Trouble Code (DTC) Information using the scan tool.

Does the scan tool indicate DTC P1154 test failed?

--

Go to Step 3

Go to Diagnostic Aids

3 | Did the scan tool also indicate P1134 test failed? | -- | Go to Step 8 | Go to Step 4
4 |

1. Inspect the exhaust system for leaks. Refer to Exhaust Leakage in Engine Exhaust.
2. If you find an exhaust leak, repair the exhaust as necessary.

Did you isolate an exhaust leak?

--

Go to Step 13

Go to Step 5

5 | Visually/physically inspect the following items:

• | Ensure that the HO2S is securely installed.

• | Inspect for corrosion on the terminals.

• | Test the terminal tension at the HO2S and at the PCM connector. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

• | Inspect for damaged wiring. Refer to Wiring Repairs in Wiring Systems.

Did you find a condition in any of the above areas?

--

Go to Step 9

Go to Step 6

6 |

1. Disconnect the Bank 2 HO2S 1.
2. Jumper the HO2S low (PCM side) signal circuit to a ground.
3. Monitor the Bank 2 HO2S 1 voltage using the scan tool.

Is the HO2S voltage within the specified range?

350-550 mV

Go to Step 7

Go to Step 10

7 |

1. Jumper the Bank 2 HO2S 1 high and low (PCM side) signal circuits to a ground.
2. Monitor the Bank 2 HO2S 1 voltage using the scan tool.

Is the HO2S voltage below the specified value?

200 mV

Go to Step 12

Go to Step 11

8 | Important: Before replacing a sensor, determine and correct the cause of the contamination. Inspect for the following conditions:

• | Fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | Use of improper RTV sealant.

• | Engine oil/coolant consumption.

Replace the affected Heated Oxygen sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 or Heated Oxygen Sensor Replacement - Bank 2 .

Is the action complete?

--

Go to Step 13

--

9 | Repair the condition as necessary. Is the action complete? | -- | Go to Step 13 | --
10 | Repair the open Bank 2 HO2S 1 low signal circuit or grounded Bank 2 HO2S 1 high signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 13 | --
11 | Repair the open Bank 2 HO2S 1 high signal circuit or faulty PCM connections. Refer to Wiring Repairs or Intermittents and Poor Connections Diagnosis in Wiring Systems. Is the action complete? | -- | Go to Step 13 | --
12 | Replace the Bank 2 HO2S 1. Refer to Heated Oxygen Sensor Replacement - Bank 2 . Is the action complete? | -- | Go to Step 13 | --
13 |

1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
2. Idle the engine at the normal operating temperature.
3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 14

Go to Step 2

14 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK