For 1990-2009 cars

### Circuit Description

The powertrain control module (PCM) supplies a voltage of about 450 mV between the oxygen sensor (O2S 1) high signal and the low signal circuit. The O2S 1 varies the voltage within a range of about 1000 mV if the exhaust is rich, down through about 100 mV if the exhaust is lean.

The sensor is like an open circuit and produces no voltage when below 315°C (600°F). An open sensor signal circuit or a cold sensor causes an Open Loop operation.

### Conditions For Running The DTC

• | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.

• | The battery voltage is greater than 10 volts.

• | The fuel level is greater than 10 percent.

• | The engine coolant temperature is greater than 70°C (158°F).

• | The air flow is more than 3 g/s.

• | The throttle position (TP) angle is between 8-56 percent.

• | The manifold absolute pressure (MAP) is greater than 25 kPa.

• | The engine run time is more than 30 seconds.

### Conditions For Setting The DTC

The O2S 1 voltage is between 399-499 mV for 125 seconds.

### 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.

### Diagnostic Aids

The normal scan tool voltage varies between 150-850 mV while in a Closed Loop operation.

An intermittent could be the result of the following conditions:

• | Poor electrical connection

• | Rubbed through wire insulation

• | Broken wire inside the insulation

Inspect for a poor electrical connection or for a damaged harness. Inspect the harness electrical connectors for the following conditions:

• | Improper mating

• | Broken locks

• | Improperly formed electrical connectors

• | Damaged terminals

• | A poor terminal to wire connection

• | A damaged harness

### Test Description

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

1. When the system is operating correctly the O2S voltage should toggle above and below the specified values.

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.

#### P0134 (Pre)

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
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 H02S DTCs), refer to other DTCs first before proceeding with this table.

1. Engine is at operating temperature.
2. Operate engine above 1,200 RPM for two minutes.
3. With a scan tool, observe the 02 voltage parameter.

Does scan tool indicate 02 voltage varying outside the specified values?

400-500 mV

Go to Step 3

Go to Step 4

3 | Operate vehicle within Fail Records conditions. Does the scan tool indicate this DTC failed this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids
4 | Inspect and test for the following:

• | Exhaust leak. Refer to Exhaust Leakage in Engine Exhaust.

• | The 02 is installed correctly.

• | Damaged wiring. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 5

5 |

1. Turn OFF the ignition.
2. Disconnect the O2S sensor.
3. Jumper the O2S low signal circuit to a good ground.
4. Turn ON the ignition, with the engine OFF.
5. Measure the voltage on the O2S high signal circuit on the PCM side, using a DMM that is connected to a good ground.

Does the voltage measure within the specified value?

451-551 mV

Go to Step 6

Go to Step 8

6 |

1. Jumper the high signal circuit to the low signal circuit (PCM side).
2. With a scan tool, observe O2S voltage parameter.

Does the scan tool indicate O2S voltage at or near the specified value?

0 mV

Go to Step 9

Go to Step 7

7 | Test the low signal circuit for an open or high resistance or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11
8 | Test the high signal circuit for an open or high resistance or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11
9 | Inspect for poor connections at the harness connector of the O2S sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10
10 | Important: Determine the cause of contamination before replacing the sensor.

1. Inspect and test for the following:

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

• | Engine oil or coolant consumption. Refer to Oil Consumption Diagnosis in Engine Mechanical.

Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.

• | Use of improper RTV sealant

2. Replace the O2S sensor. Refer to Oxygen Sensor Replacement .

Did you complete the replacement.

--

Go to Step 13

--

11 | Test for poor connections at 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 13 | Go to Step 12
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | --
13 |

1. Use a scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 14

Go to Step 2

14 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK