[Previous][Next]
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 line 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 heater monitor
  • Heated oxygen sensor (rear) heater monitor
  • Heated oxygen sensor offset voltage monitor
Sensor (The sensor below is determined to be normal)
  • Linear air-fuel ratio sensor
  • Mass airflow sensor
  • Engine coolant temperature sensor
  • Intake air temperature sensor 1
  • Barometric pressure sensor
 
 
DTC SET CONDITIONS
Logic Flow Chart
 
 
Check Conditions
  • Engine coolant temperature is more than 76°C (169°F).
  • The linear air-fuel ratio sensor is active.
  • The cumulative mass airflow sensor output is more than 1,638 g.
  • Fuel is being shut off.
  • Heated oxygen sensor (rear) output voltage is more than 0.5 volt when fuel cut is started.
  • It has been taking more than 180 seconds 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).
  • Sum of Air flow rate accumulated during open loop operation and subtracted during fuel cut or closed loop operation is less than 200 g.
  • Sum of Air flow rate accumulated during fuel cut before heated oxygen sensor (rear) drops below 0.5 volt is more than 13 g. <From 19 Model year>
Judgment Criterion
  • Heated oxygen sensor (rear) output voltage does not reach 0.2 volt for 6 seconds from fuel cut start. <Up to 18 Model year>
  • Heated oxygen sensor (rear) output voltage does not reach 0.2 volt for 3 seconds from fuel cut start. <From 19 Model year>
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 higher than 1,638 g.
  • Fuel is being shut off.
  • The heated oxygen sensor (rear) output voltage is higher than 0.5 volt when fuel cut is started.
  • It has been taking more than 180 seconds 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).
  • The ECM monitors for this condition for 3 cycles of 0.3 second each during drive cycles.
  • Sum of Air flow rate accumulated during open loop operation and subtracted during fuel cut or closed loop operation is less than 200 g.
  • Sum of Air flow rate accumulated during fuel cut before heated oxygen sensor (rear) drops below 0.5 volt is more than 2.5 g.
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 after fuel has been shut off for more than 64 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • None.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 17 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Heated oxygen sensor (rear) failed.
  • 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 the ignition switch to the "LOCK" (OFF) position 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) Start the engine and run at idle.
(3) Set scan tool (M.U.T.-IIISE) to the data reading mode for item AD, Heated Oxygen Sensor (rear).
  1. Transaxle: 2nd
  2. Drive with wide open throttle
  3. Engine: 3,500 r/min or more
    • The output voltages should be between 0.6 and 1.0 volt.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
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 17 .
(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.