Advanced Diagnostics

Advanced Diagnostics - DTC P0135: Air/Fuel Ratio (A/F) Sensor (Sensor 1) Heater Circuit Malfunction






General Description
A heater for the sensor element is embedded in the air/fuel ratio (A/F) sensor (sensor 1), and it is controlled by the engine control module (ECM)/powertrain control module (PCM). It is activated and heats the sensor to stabilize and speed up the detection of oxygen content when the exhaust gas temperature is cold. If the A/F sensor (sensor 1) heater current is not a set value, or the heater is overheated, the ECM/PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
Case 1
The heater current is 0.8 A or less for at least 4 seconds while the heater is activated, and the heater current is 0.8 A or more for at least 4 seconds while the heater is not activated.

Case 2
The heater current is 15.2 A or more for at least 0.6 second.

Driving Pattern
Start the engine. Hold the engine speed at 3,000 rpm without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the ECM/PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.