DTC P0135: Heated Oxygen Sensor Heater Circuit (sensor 1)

CIRCUIT OPERATION
• Power is supplied from the MFI relay (terminal No. 4) to the heated oxygen sensor (front) heater.
• The ECM (terminal No. 60) <M/T> or PCM (terminal No. 3) <A/T> controls continuity to the heated oxygen sensor (front) heater by turning the power transistor in the ECM <M/T> or PCM <A/T> "ON" and "OFF".
TECHNICAL DESCRIPTION
• The ECM <M/T> or PCM <A/T> checks whether the heater current is within a specified range when the heater is energized.
DESCRIPTIONS OF MONITOR METHODS
• An open or short circuit is detected while monitoring the amperage that flows to the heated oxygen sensor (front) at the engine coolant temperature of 20°C (68°F) or above.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)

Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
• Not applicable

Sensor (The sensor below is determined to be normal)
• Engine coolant temperature sensor
DTC SET CONDITIONS Logic Flow Chart


Check Conditions
60 seconds have elapsed from the start of the previous monitoring.
Engine coolant temperature is higher than 20°C (68°F).
While the heated oxygen sensor (front) heater is on.
Battery positive voltage is at between 11 and 16.5 volts.

Judgment Criterion
• Heater current of the heated oxygen sensor (front) heater has continued to be lower than 0.16 ampere or higher than 7.5 ampere for 4 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 2 .
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
• Open or shorted heated oxygen sensor (front) heater circuit.
• Open circuit in heated oxygen sensor (front) heater.
• ECM failed. <M/T>
• PCM failed. <A/T>