For 1990-2009 cars

The heated oxygen sensor 1 (H02S-1) is an electrical source that responds to oxygen content in the exhaust manifold. When the sensor reaches approximately 316°C (600°F), it produces a voltage based on the difference in oxygen between the atmosphere and exhaust gas. When the HO2S-1 is cold, it produces no voltage and has extremely high internal resistance. The internal resistance of the sensor is much greater than the resistance of the bias pull-up resistor. A heater element is required to provide additional heat which accelerates sensor activation time. The heater is supplied ignition is turned ON and the PCM provides a ground when the conditions necessary to perform the test are met. The PCM will monitor the heater current to determine if the heater is working properly. DTC P0135 sets when the HO2S-1 heater current is not within the calibrated range.

### DTC PARAMETERS

DTC P0135 will set if HO2S-1 heater current is less than 0.2 A or greater than 1.5 A:

• | The engine run time is greater than 60 seconds.

• | The ECT is greater than 70°C (158°F).

• | The ignition voltage is greater than 10 V.

• | The air flow is less than 25 g/s (manual) or 40 g/s (auto).

• | The fuel level is greater than 10 percent.

• | No CKP, ECT, EVAP, fuel injector, fuel tank pressure, fuel trim, IAT, idle speed, MAP, misfire, PCM internal fault, or TP sensor DTCs have been set.

DTC P0135 diagnostic runs continuously once the above conditions have been met.

P0135 is a type B DTC.

### Diagnostic Aids

Heater element resistance: 11.7-14.3 ohms

Normal operating range 0.6-0.7 amps