P0135

DTC P0135

CIRCUIT DESCRIPTION
The 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. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. Ground is provided to the heater on the low control circuit by a low side driver within the control module. The control module monitors the current draw of the heater to determine if a failure is present.

If the ECM detects that the HO2S 1 heater current is below a specified value, this DTC sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0135 HO2S Heater Performance Sensor 1

CONDITIONS FOR RUNNING THE DTC
- DTCs P0106, P0107, P0117, and P0118 are not set.
- The engine run time is more than 3 minutes.
- The ignition 1 voltage is more than 10 volts.
- The manifold absolute pressure (MAP) is less than 65 kPa.
- DTC P0135 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
The ECM detects that the HO2S 1 heater current is less than 0.1 amps for 3 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.

TEST DESCRIPTION

Steps 1-3:

Steps 4-7:

Steps 8-11:

Steps 12-16:

Step 17:

The number below refers to the step number on the diagnostic table.
6. This step is testing the heater control circuit for a short to ground.
7. This step is testing the heater control circuit for an open or for a short to voltage.
8. This step is testing the heater control circuit for high resistance. If the voltage is more than the specified value, test the circuit for high resistance.