P0139
Heated Oxygen Sensor (rear) Circuit:
Connectors:
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal 75)
- Terminal 2 of the heated oxygen sensor (rear) is grounded with ECM (terminal 92)
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
DTC SET CONDITIONS
Check Conditions
- Engine coolant temperature is higher than 76 °C (169 °F).
- The heated oxygen sensor (front) is active.
- The cumulative volume air flow sensor output frequency is higher than 4,000 Hz.
- 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 (18.7 mph).
- A total of more than 10 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 (0.9 mph).
Judgement Criteria
- Change in the output voltage of the heated oxygen sensor (rear) is lower than 0.078 volt.
NOTE: Monitoring stops after fuel has been shut off for more than 38 seconds.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Heated oxygen sensor (rear) failed.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tools
- MB991502: Scan Tool (MUT-II)
STEP 1. Using scan tool MB991502, check data list item 59: Heated Oxygen Sensor (rear).
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 59, Heated Oxygen Sensor (rear).
4. Warm up the engine.
- Warming up the engine. When the engine is revved, the output voltage should repeat 0 volt and 0.6 to 1.0 volt alternately.
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 Procedure 4 - Heated Oxygen Sensor Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is the DTC P0139 output?
YES: Retry the troubleshooting.
NO: The inspection is complete.