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 ECM (terminal No. 74)
- Terminal No. 2 of the right bank heated oxygen sensor (rear) is grounded with ECM (terminal No. 49)
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 ECM
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)
- 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
- 2 seconds or more have passed since the 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) ground line.
- ECM failed.
- PCM failed.
- Connector damage.
DIAGNOSIS
Required Special Tool:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B
STEP 1. Check connector B-28 at right bank heated oxygen sensor (rear) and connector C-62 at ECM
Q: Is the 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-28 (terminal No. 4) and ECM connector C-62 (terminal No. 74)
Q: Is the harness wire in good condition?
YES: Replace the ECM or 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.