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 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
DTC SET CONDITIONS
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.
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
Required Special Tool:
- MB991502: Scan Tool (MUT-II)
STEP 1. Check connector C-11 at heated oxygen sensor (rear) and connector C-115 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 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. Perform the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis- OBD-II Drive Cycle - Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0138 set?
YES: Repeat the troubleshooting.
NO: The procedure is complete.