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P0134




DTC P0134 HO2S Circuit Insufficient Activity Bank 1 Sensor 1






Circuit Description

The powertrain control module (PCM) supplies a voltage of about 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if majority of the samples are out of the operating range.

The PCM monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the PCM does not detect the voltage went out of the bias range, this DTC will set.

Conditions for Running the DTC

* DTCs P0102, P0103, P0112, P0113, P0117, P0118, P0335, P0336, P1120, P1220, P1221 not set
* The ignition voltage is more than 9.0 volts
* The fuel system is operating in Closed Loop
* The engine run time is more than 70 seconds

Conditions for Setting the DTC

* The engine coolant temperature is more than 60°C (140°F)
* The HO2S signal voltage is steady between 350 mV and 550 mV
* The conditions present for 60 seconds

Action Taken When the DTC Sets

* The PCM illuminate the malfunction indicator lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails, if the diagnostic fails under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed.
* The first time the diagnostic fails, the PCM records the operating conditions in Failure Records.
* The second consecutive drive trip that this diagnostic fails under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed, the PCM stores this information in Freeze Frame. The PCM copies any data previously stored in Freeze Frame and copies the data into the Failure Records. The PCM then overwrites the Freeze Frame and the PCM updates the HO2S data in the Failure Records.
* Open Loop Fueling.

Conditions for Clearing the MIL/DTC

Important: If the last failure was during a non-typical driving condition, the MIL may remain ON longer than the three drive trips. Review the Freeze Frame and Failure Records for the last failure conditions.


* The PCM turns the MIL OFF after 3 consecutive drive trips that the diagnostic runs and does not fail within the same conditions that the DTC last failed.
* A History DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
* A last test failed (Current DTC) clears when the diagnostic runs and does not fail.
* The PCM battery voltage is interrupted.
* Use a scan tool in order to clear the MIL/DTC.

Diagnostic Aids

Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.


* Inspect the PCM connector.
* An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination. Refer to Wiring Repairs Wiring Repairs in Wiring Systems.
* Using the Freeze Frame and Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and a fail. Operate the vehicle within the same Freeze Frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.
* For an intermittent condition, refer to Symptoms Symptoms.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. The engine must be at the normal operating temperature before performing this test. For any test that requires probing the PCM or a component harness connector, use the connector test adapter kit. Using this kit prevents damage to the harness connector terminals.
3. Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you can not duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine 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 the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that the PCM recorded. This will isolate when the DTC failed. Refer to Symptoms.
4. If the scan tool indicates the HO2S voltage goes below 200 mV, this indicates the HO2S circuits and PCM are OK.
5. This step checks whether the signal circuit from the PCM is OK.
6. Disconnecting the PCM allows using a DMM in order to check continuity of the circuits. This aids in locating an open or shorted circuit.
7. Disconnecting the PCM allows using a DMM in order to check continuity of the circuits. This aids in locating an open or shorted circuit.









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