DTC P0156: Heated Oxygen Sensor Circuit (bank 2, sensor 2)

CIRCUIT OPERATION
• A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the PCM (terminal No. 73) from the output terminal (terminal No. 4) of the left bank heated oxygen sensor (rear).
• Terminal No. 2 of the left bank heated oxygen sensor (rear) is grounded with PCM (terminal No. 57).
TECHNICAL DESCRIPTION
• The output signal of the left bank heated oxygen sensor (front) is compensated by the output signal of the left bank heated oxygen sensor (rear).
• The PCM checks for an open circuit in the left bank heated oxygen sensor (rear) output line.
DESCRIPTIONS OF MONITOR METHODS
Left bank heated oxygen sensor (rear) circuit is switched to 5 volts intentionally when oxygen sensor output is low, and detects the malfunction if the output voltage changes to equal or greater than 4.5 volts. The above procedure is repeated when oxygen sensor is inactive.
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)
• Heated oxygen sensor heater (front) monitor
• Heated oxygen sensor heater (rear) monitor
• Air/fuel ratio feedback monitor

Sensor (The sensor below is determined to be normal)
• Volume airflow sensor
• Engine coolant temperature sensor
• Intake air temperature sensor
• Barometric pressure sensor
DTC SET CONDITIONS Logic Flow Chart


Check Conditions
• 3 minutes or more have passed since the starting sequence was completed.
• Left bank heated oxygen sensor (rear) signal voltage has continued to be 0.15 volt or lower.
• Engine coolant temperature is higher than 76°C (169°F).
• Engine speed is higher than 1,200 r/min.
• Volumetric efficiency is higher than 25 percent.
• Monitoring time: 7 seconds.

Judgment Criteria
• Input voltage supplied to the PCM interface circuit is higher than 4.5 volts when 5 volts is applied to the left bank heated oxygen sensor (rear) output line via a resistor.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor .
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:
• Left bank heated oxygen sensor (rear) failed.
• Open circuit in left bank heated oxygen sensor (rear) output line.
• Open circuit in left bank heated oxygen sensor (rear) ground line or harness damage.
• Connector damage.
• PCM failed.