P0138

DTC P0138: Heated Oxygen Sensor Circuit High Voltage (bank 1, sensor 2)

Right Bank Heated Oxygen Sensor (Rear) Circuit Part 1:

Right Bank Heated Oxygen Sensor (Rear) Circuit Part 2:

CIRCUIT OPERATION
- A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the PCM (terminal No. 97) from the output terminal (terminal No. 4) of the right bank heated oxygen sensor (rear).
- Terminal No. 2 of the right bank heated oxygen sensor (rear) is grounded with PCM (terminal No. 69).

TECHNICAL DESCRIPTION
- The output signal of the right bank heated oxygen sensor (front) is compensated by the output signal of the right bank heated oxygen sensor (rear).
- The PCM checks for an open circuit in the right bank heated oxygen sensor (rear) output line.

DESCRIPTIONS OF MONITOR METHODS
Right bank heated oxygen sensor (rear) output voltage is over specified range

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
- 2 seconds or more have passed since the engine starting sequence was completed

Judgment Criteria
- Right bank heated oxygen sensor (rear) output voltage has continued to be 1.2 volts or higher for 2 seconds.

OBD-II DRIVE CYCLE PATTERN

Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor. OBD-II Drive Cycle Pattern Lists

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Short circuit in right bank heated oxygen sensor (rear) output line.
- Connector damage.
- 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. Check harness connector B-08 at right bank heated oxygen sensor (rear) and harness connector B-22 at PCM for damage.

Q: Is the harness connector in good condition?

YES: Go to Step 2.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 3.







STEP 2. Check for short circuit to power supply between right bank heated oxygen sensor (rear) connector B-08 (terminal No. 4) and PCM connector B-22 (terminal No. 97).

Q: Is the harness wire in good condition?

YES: Replace the PCM. Then go to Step 3.

NO: Repair it. Then go to Step 3.

STEP 3. 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 6 - Other Monitor. OBD-II Drive Cycle Pattern Lists
2. Check the diagnostic trouble code (DTC).

Q: Is DTC P0138 set?

YES: Retry the troubleshooting.

NO: The inspection is complete.