DTC P0151: Heated Oxygen Sensor Circuit Low Voltage (bank 2, sensor 1)

CIRCUIT OPERATION
• A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the PCM (terminal No. 71) from the output terminal (terminal No. 4) of the left bank heated oxygen sensor (front).
• Terminal No. 2 of the left bank heated oxygen sensor (front) is grounded with PCM (terminal No. 57).
TECHNICAL DESCRIPTION
• The left bank heated oxygen sensor (front) detects the concentration of oxygen in the exhaust gas; it converts that data to voltage, and sends it to the PCM.
• When the left bank heated oxygen sensor (front) begins to deteriorate, the heated oxygen sensor signal response deteriorates also.
• The PCM varies the air/fuel mixture to make it leaner and richer, and checks the response speed of the left bank heated oxygen sensor (front). In addition, the PCM also checks for an open circuit in the left bank heated oxygen sensor (front) output line.
DESCRIPTIONS OF MONITOR METHODS
Left bank heated oxygen sensor (front) output voltage stays low when air/fuel ratio is forced to be rich. 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
• Misfire monitor
• Fuel system monitor

Sensor (The sensor below is determined to be normal)
• Volume airflow sensor
• Engine coolant temperature sensor
• Intake air temperature sensor
• Barometric pressure sensor
• Throttle position 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 (front) signal voltage has continued to be 0.2 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.
Volume airflow sensor output frequency is 100 Hz or more.
At least 20 seconds have passed since fuel shut off control was canceled.
Monitoring time: 10 seconds.

Judgement Criteria
• Making the air/fuel ratio 15 percent for 10 seconds richer does not result in raising the heated oxygen sensor (front) output voltage beyond 0.2 volt.
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 (front) failed.
• Short circuit in left bank heated oxygen sensor (front) output line, or harness damage.
• PCM failed.