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DTC P0139: Heated Oxygen Sensor (rear) Circuit Slow Response
 
 
 
 
CIRCUIT OPERATION
  • A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM terminal O2RL from the output terminal of the heated oxygen sensor (rear).
  • Terminal ORLE of the heated oxygen sensor (rear) is grounded with ECM terminal ORLE.
  • The ECM applies an offset voltage of 0.5 volt to ground terminal of the heated oxygen sensor (rear)
 
 
TECHNICAL DESCRIPTION
  • The output signal of the linear air-fuel ratio sensor is compensated by the output signal of the heated oxygen sensor (rear).
  • The ECM checks for the heated oxygen sensor (rear) output voltage.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Heated oxygen sensor (rear) output voltage does not reach 0.2 volt after fuel cut operation.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC set in memory for the item monitored below)
  • Linear air-fuel ratio sensor monitor
  • Linear air-fuel ratio sensor heater monitor
  • Heated oxygen sensor (rear) heater monitor
  • Heated oxygen sensor offset voltage monitor
Sensor (The sensor below is determined to be normal)
  • Mass airflow sensor
  • Engine coolant temperature sensor
  • Intake air temperature sensor
  • Barometric pressure sensor
  • Fuel tank pressure sensor
 
 
DTC SET CONDITIONS
Logic Flow Chart
 
 
Check Conditions
  • Engine coolant temperature is higher than 76°C (169°F).
  • The linear air-fuel ratio sensor is active.
  • The cumulative mass airflow sensor output is lower than 200 g, while the open loop air-fuel ratio control.
  • The cumulative mass airflow sensor output is higher than 15 g before the heated oxygen sensor (rear) output voltage reaches 0.5 volt while fuel is being shut off.
  • Fuel is being shut off.
  • Heated oxygen sensor (rear) output voltage is 0.5 volt or higher when fuel cut is started.
  • It has been taking 180 seconds or more since the drive signal of the heated oxygen sensor (rear) heater was turned on.
  • Barometric pressure is higher than 76 kPa (22.4 in.Hg).
  • 5 seconds or more have passed since the estimated catalytic converter temperature is higher than 652°C (1,206°F).
Judgment Criterion
  • Heated oxygen sensor (rear) output voltage does not reach 0.2 volt for 3 seconds from fuel cut start.
Check Conditions
  • Engine coolant temperature is higher than 76°C (169°F).
  • The linear air-fuel ratio sensor is active.
  • The cumulative mass airflow sensor output is lower than 200 g, while the open loop air-fuel ratio control.
  • The cumulative mass airflow sensor output is higher than 2 g before the heated oxygen sensor (rear) output voltage reaches 0.5 volt while fuel is being shut off.
  • Fuel is being shut off.
  • Heated oxygen sensor (rear) output voltage is 0.5 volt or higher when fuel cut is started.
  • It has been taking 180 seconds or more since the drive signal of the heated oxygen sensor (rear) heater was turned on.
  • Barometric pressure is higher than 76 kPa (22.4 in.Hg).
  • 5 seconds or more have passed since the estimated catalytic converter temperature is higher than 652°C (1,206°F).
  • The ECM monitors for this condition for 3 cycles of 0.3 second each during drive cycles.
Judgment Criteria
  • The heated oxygen sensor (rear) output voltage does not reach 0.2 volt for 0.3 second from 0.4 volt while fuel is being shut off.
  • The ECM monitors for this condition once during the drive cycle.
noteMonitoring stops when the estimated catalytic converter temperature is 600°C (1,112°F) or lower.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • None.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 4 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Heated oxygen sensor (rear) deteriorated.
  • Connector damage.
  • ECM failed.

 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), check data list item AD: Heated Oxygen Sensor (rear).
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
(1) Connect scan tool (M.U.T.-IIISE). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) .
(2) Set the vehicle to the continuous idling mode.
(3) Set scan tool (M.U.T.-IIISE) to the data reading mode for item AD, Heated Oxygen Sensor (rear).
(4) Warm up the engine.
  • After increasing the output voltage 0.5 volt or more by the engine revving, finish it. Then confirm that the output voltage reduces to 0.2 volt or less within 6 seconds.
(5) Turn off the power supply mode of the electric motor switch.
Is the sensor operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Replace the heated oxygen sensor (rear). Then go to Step 2.
 
STEP 2. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 4 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0139 set?
Refer to DTC P0137 - Heated Oxygen Sensor (rear) Circuit Low Voltage , DTC P0138 - Heated Oxygen Sensor (rear) Circuit High Voltage .
The inspection is complete.