P0138
DTC P0138: Heated Oxygen Sensor Circuit High Voltage (sensor 2)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)
- 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
DESCRIPTIONS OF MONITOR METHODS
- If the heated oxygen sensor (rear) output is higher than the standard value while monitoring the heated oxygen sensor (rear) output, a short circuit (short circuit to power supply) is determined to have occurred.
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
- 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:)
- Heated oxygen sensor (rear) failed.
- Short circuit in heated oxygen sensor (rear) output line.
- ECM failed.
- PCM failed.
DIAGNOSIS
STEP 1. Check harness connector C-11 at heated oxygen sensor (rear) and harness connector C-115 at ECM
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 heated oxygen sensor (rear) connector C-11 (terminal No.1) and ECM connector C-115 (terminal No.75)
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.