For 1990-2009 cars

### Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperatures and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.

This diagnostic will only run once per ignition cycle. The PCM monitors the number of rich-to-lean and lean-to-rich transitions. A transition is defined as the HO2S voltage changes from above 600 mV to below 300 mV or from below 300 mV to above 600 mV. If the PCM detects that the transition time ratio is not within a specified range, DTC P1134 will set.

### Conditions for Running the DTC

• | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0128, P0201-P0204, P0300, P0301-P0304, P0336, P0410, P0440, P0442, P0446, P0452, P0453, P0506, P0507, P0601, P0602, P1441, or P1621 are not set.

• | The engine coolant temperature (ECT) sensor parameter is more than 70°C (158°F).

• | The engine speed parameter is between 1,000-3,500 RPM.

• | The ignition 1 signal parameter is more than 10 volts.

• | The engine run time parameter is more than 200 seconds.

• | The Loop Status parameter is closed.

• | The throttle position (TP) angle parameter is between 5-40 percent.

• | The evaporative emission (EVAP) purge solenoid DC is more than 35 percent.

• | The fuel level sensor parameter is more than 10 percent.

• | The manifold absolute pressure (MAP) sensor parameter is between 10-104 kPa.

• | The above conditions are met for 60 seconds.

### Conditions for Setting the DTC

The PCM detects that the HO2S 1 rich-to-lean or lean-to-rich average transition time ratio is not within a calibrated range.

### Action Taken When the DTC Sets

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

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

### Conditions for Clearing the MIL/DTC

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

• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

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

• | Clear the MIL and the DTC with a scan tool.

### Test Description

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

1. When the system is operating correctly, the HO2S 1 voltage should toggle above and below the specified values. You may need to operate the vehicle within the Freeze Frame conditions and Conditions for Setting the DTC in order to duplicate the malfunction that was detected by the PCM.

2. The specified value is what is measured on a correctly operating system.

3. The specified value is what is measured on a correctly operating system.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 | Important: If any other DTCs are set except for heated oxygen sensor (HO2S) DTCs, refer to the other DTCs first before proceeding with this table.

1. Operate the engine at normal operating temperature.
2. Operate the engine above 1,200 RPM for 2 minutes.
3. Observe the HO2S 1 voltage parameter with a scan tool.

Does the scan tool indicate that the HO2S 1 voltage is varying above and below the specified values?

350-550 mV

Go to Step 3

Go to Step 4

3 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4 |

1. Turn OFF the ignition.
2. Disconnect the HO2S 1.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage of the HO2S 1 high signal circuit on the powertrain control module (PCM) side to a good ground with a DMM.

Does the voltage measure within the specified value?

350-550 mV

Go to Step 5

Go to Step 9

5 |

1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit and the HO2S 1 low signal circuit.
3. Turn ON the ignition.
4. Monitor the HO2S 1 voltage for the sensor that applies to this DTC with a scan tool.

Does the scan tool indicate that the HO2S 1 voltage is less than the specified value?

20 mV

Go to Step 6

Go to Step 10

6 |

1. Turn OFF the ignition.
2. Remove the 3-amp fused jumper wire.

Important: Do not use the HO2S 1 heater low control.

3. Connect a test lamp between the ignition 1 voltage circuit and a good ground.
4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 11

7 |

1. Connect a test lamp between the ignition 1 voltage circuit and the HO2S 1 heater low control circuit.
2. Turn ON the ignition, with the engine OFF.
3. Command the HO2S 1 heater ON and OFF with a scan tool.

Does the test lamp turn ON and OFF with each command?

--

Go to Step 14

Go to Step 8

8 | Does the test lamp remain illuminated with each command? | -- | Go to Step 12 | Go to Step 13
9 | Test the HO2S 1 high signal circuit for the following conditions:

• | An open

• | A short to ground

• | A short to voltage

• | High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 16

10 | Test the HO2S 1 low signal circuit for the following conditions:

• | An open

• | A short to voltage

• | High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 16

11 |

1. Test the ignition 1 voltage circuit for the following conditions:

• | An open

• | A short to ground

• | High resistance

• | Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

2. Replace the EIS fuse if necessary.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

12 | Test the HO2S 1 heater low control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16
13 | Test the HO2S 1 heater low control circuit for the following conditions:

• | An open

• | A short to voltage

• | High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 16

14 | Important: Before replacing the HO2S 1, inspect for and remove any source of contamination. Inspect for the following conditions:

• | The use of incorrect silicon RTV sealant

• | Fuel contamination

• | An exhaust leak

| Refer to Exhaust Leakage in Engine Exhaust.

• | The HO2S is installed correctly

• | Damaged wiring

| Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

15 | Inspect for poor connections at the harness connector of the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 17
16 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18
17 | Replace the HO2S 1. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
18 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 19 | --
19 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 20

20 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK