P0139

DTC P0139: Heated Oxygen Sensor Circuit Slow Response

Heated Oxygen Sensor (rear) Circuit Part 1:

Heated Oxygen Sensor (rear) Circuit Part 2:

CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM (terminal No. 75) from the output terminal (terminal No. 1) of the heated oxygen sensor (rear).
- Terminal No. 2 of the heated oxygen sensor (rear) is grounded with ECM (terminal No. 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 checks for an open circuit in the heated oxygen sensor (rear) output line.

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)
- Volume 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 volume airflow sensor output frequency is higher than 10,000 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 (19 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 (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) failed.
- Connector damage.
- ECM failed.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
- MB991658: Test Harness Set




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.
- Warm 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. Check the heated oxygen sensor (rear).




1. Disconnect the heated oxygen sensor (rear) connector D-40 and connect test harness special tool, MB991658, to the connector on the heated oxygen sensor (front) side.
2. Warm up the engine until engine coolant 80 °C (176 °F) or higher.

CAUTION: Be very careful when connecting the jumper wires; incorrect connection can damage the right bank heated oxygen sensor (rear).




3. Use the jumper wires to connect terminal No. 3 to the positive battery terminal and terminal No. 4 to the negative battery terminal.
4. Connect a digital volt meter between terminal No. 1 and terminal No. 2.
5. While repeatedly revving the engine, measure the heated oxygen sensor (rear) output voltage.

Standard value: 0.6 - 1.0 volt

Q: Is the voltage between 0.6 and 1.0 volt?

YES: Go to Step 3.

NO: Replace the heated oxygen sensor (rear). Then go to Step 4.







STEP 3. Check harness connector D-40 at heated oxygen sensor (rear) and harness connector C-115 at ECM for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 4.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 4.

STEP 4. Perform 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: Repeat the troubleshooting.

NO: The procedure is complete.