P0139

DTC P0139: Cylinder 1, 4 Heated Oxygen Sensor (rear) Circuit Slow Response

Cylinder 1, 4 Heated Oxygen Sensor (rear) Circuit Part 1:

Cylinder 1, 4 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 or the PCM (terminal No. 97) from the output terminal (terminal No. 4) of the cylinder 1, 4 heated oxygen sensor (rear).
- Terminal No. 2 of the cylinder 1, 4 heated oxygen sensor (rear) is grounded with ECM or PCM (terminal No. 106).
- The ECM or the PCM applies an offset voltage of 0.5 volt to terminal No. 2 of the cylinder 1, 4 heated oxygen sensor (rear)

TECHNICAL DESCRIPTION
- The output signal of the cylinder 1, 4 heated oxygen sensor (front) is compensated by the output signal of the cylinder 1, 4 heated oxygen sensor (rear).
- The ECM or the PCM checks for the cylinder 1, 4 heated oxygen sensor (rear) output voltage.

DESCRIPTIONS OF MONITOR METHODS
Cylinder 1, 4 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 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 degrees C (169 degrees F).
- The cylinder 1, 4 heated oxygen sensor (front) is active.
- The cumulative mass airflow sensor output is higher than 1,638 g.
- Fuel is being shut off.

Judgement Criterion
- Cylinder 1, 4 heated oxygen sensor (rear) output voltage does not reach 0.2 volt for 6 seconds from fuel cut start.

OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 11. OBD-II Drive Cycle Pattern Lists

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Cylinder 1, 4 heated oxygen sensor (rear) deteriorated.
- Connector damage.
- ECM failed.
- PCM failed.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A

STEP 1. Replace the cylinder 1, 4 heated oxygen sensor (rear).

1. Replace the cylinder 1, 4 heated oxygen sensor (rear).
2. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 11. OBD-II Drive Cycle Pattern Lists
3. Check the diagnostic trouble code (DTC).

Q: Is DTC P0139 set?

YES: Refer to DTC P0137 - Cylinder 1, 4 Heated Oxygen Sensor (rear) Circuit Low Voltage, DTC P0138 - Cylinder 1, 4 Heated Oxygen Sensor (rear) Circuit High Voltage.

NO: The inspection is complete.