P0139
Connectors:
DIAGNOSIS
Required Special Tools
MB991502: Scan Tool(MUT-II)
CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal 75)
- Terminal 4 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
- Heated oxygen sensor (rear) signal voltage has continued to be 0.15 volt or lower for three minutes or more after the starting sequence was completed.
- Engine coolant temperature is higher than 82 °C (180 °F).
- Engine speed is higher than 1,200 r/min.
- Volumetric efficiency is higher than 25 percent.
- Volume air flow sensor output frequency is 88 Hz or more.
- At least twenty seconds have passed since fuel shut off control was canceled.
- The heated oxygen sensor (front) outputs 0.5 volts or more.
- 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 (rear) output voltage beyond 0.15 volt.
- Only one monitor during one drive cycle
Check Conditions
- Engine coolant temperature is higher than 82 °C (180 °F).
- Barometric pressure is higher than 76 kPa (11 psi).
- The heated oxygen sensor (front) is active.
Judgement Criteria
- The heated oxygen sensor (rear) output voltage, before the fuel shut off is started, was 0.4 volts or more, and during the shut off, it takes one second or more for the heated oxygen sensor (rear) output voltage to fall from 0.4 to 0.15 volts.
or
- The heated oxygen sensor (rear) output voltage, before the fuel shut off is started, was 0.15 volts or more, and during the shut off, it takes three seconds or more for the heated oxygen sensor (rear) output voltage to fall below 0.15 volts.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Heated oxygen sensor (rear) failed.
- Open circuit in heated oxygen sensor (rear) output line.
- Open circuit in heated oxygen sensor (rear) ground line.
- ECM failed.
- PCM failed.
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.
- After increasing the output voltage 0.15 volts or more by the engine revving, finish it. Then confirm that the output voltage reduces to 0.15 volts 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 Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code(DTC).
Q: Is the DTC P0139 is output?
YES: Retry the troubleshooting.
NO: The inspection is complete.