P0139
DTC P0139: Heated Oxygen Sensor Circuit Slow Response (sensor 2)Heated Oxygen Sensor (rear) Circuit:
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM
- Terminal No. 2 of the heated oxygen sensor (rear) is grounded with ECM
TECHNICAL DESCRIPTION
- The output signal of the heated oxygen sensor (front) is compensated by the output signal of the heated oxygen sensor (rear).
- The ECM
DESCRIPTIONS OF MONITOR METHODS
Heated oxygen sensor (rear) output voltage does not change during specified go/stop operations including fuel cut are repeated.
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)
- Mass airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
DTC SET CONDITIONS
Logic Flow Chart:
Logic Flow Chart
Check Conditions
- Engine coolant temperature is higher than 76 °C (169 °F).
- The heated oxygen sensor (front) is active.
- The cumulative mass airflow sensor output is higher than 2,931 g.
- Repeat 3 or more times: drive*1, stop*2.
Drive*1:
- Engine speed is higher than 1,500 r/min.
- Volumetric efficiency is higher than 40 percent.
- Vehicle speed is higher than 30 km/h (19 mph).
- A total of more than 26 seconds have elapsed with the above mentioned conditions, and more than 2 seconds have elapsed with the fuel shut off.
Stop*2:
- Vehicle speed is lower than 1.5 km/h (1 mph).
Judgement Criteria
- Change in the output voltage of the heated oxygen sensor (rear) is lower than 0.313 volt.
NOTE: Monitoring stops after fuel has been shut off for more than 38 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 4 - Heated Oxygen Sensor Monitor. OBD-II Drive Cycle Pattern Lists
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Heated oxygen sensor (rear) deteriorated.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
STEP 1. Using scan tool MB991958, check data list item 59: Heated Oxygen Sensor (rear).
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991958 to the data reading mode for item 59, Heated Oxygen Sensor (rear).
4. Warm up the engine.
- After increasing the output voltage 0.15 volt or more by the engine revving, finish it. Then confirm that the output voltage reduces to 0.15 volt or less within 3 seconds.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.
NO: 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 - Procedure 4 - Heated Oxygen Sensor Monitor. OBD-II Drive Cycle Pattern Lists
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0139 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.