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DTC P0138: Heated Oxygen Sensor Circuit High Voltage (bank 1, sensor 2)
 
 
 
 
CIRCUIT OPERATION
  • A voltage corresponding to the oxygen concentration in the exhaust gas is sent to the ECM terminal O2RR from the output terminal of the right bank heated oxygen sensor (rear).
  • Terminal of the right bank heated oxygen sensor (rear) is grounded with ECM terminal ORRE.
  • The ECM applies an offset voltage of 0.5 volt to ground terminal of the right bank heated oxygen sensor (rear).
 
 
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 checks for the right bank heated oxygen sensor (rear) output voltage.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Right bank heated oxygen sensor (rear) output voltage is over the 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)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Engine coolant temperature sensor
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Right bank heated oxygen sensor (rear) output voltage is over the 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)
  • Right bank linear air-fuel ratio sensor monitor
  • Right bank linear air-fuel ratio sensor inactive monitor
  • Right bank heated oxygen sensor offset voltage monitor
  • Right bank linear air-fuel ratio sensor heater monitor
  • Right bank heated oxygen sensor (rear) heater 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
  • Throttle position sensor
 
 
DTC SET CONDITION
Logic Flow Chart
 
 
Check Conditions
  • 2 seconds or more have passed since the engine starting sequence was completed.
  • Heated oxygen sensor off set voltage is between 0.4 and 0.6 volt.
Judgment Criterion
  • Right bank heated oxygen sensor (rear) output voltage has continued to be 1.8 volts or higher for 2 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • None
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 22 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Connector damage.
  • Harness damage
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle Communication Interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite Main Harness A
  • MB992747: V.C.I.-Lite USB Cable Short
  • MB992748: V.C.I.-Lite USB Cable Long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Using scan tool (M.U.T.-III), check data list item AD: Heated Oxygen Sensor Bank 1, Sensor 2 (right rear).
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(1) Connect scan tool (M.U.T-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(2) Start the engine and run at idle.
(3) Set scan tool (M.U.T-III) to the data reading mode for item AD, Heated Oxygen Sensor Bank 1, Sensor 2 (right rear).
  1. Transaxle: 2nd
  2. Drive with wide open throttle
  3. Engine: 3,500 r/min or more
    • The output voltages should be between 0.6 and 1.0 volt.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the sensor operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Go to Step 2.
 
STEP 2. Check of short circuit to power supply in O2RR line between right bank heated oxygen sensor (rear) connector and ECM connector.
Is the harness wire in good condition?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 4.
Repair the connector(s) or wiring harness. Then go to Step 3.
 
STEP 3. Using scan tool (M.U.T.-III), check data list item AD: Heated Oxygen Sensor (rear).
(1) Start the engine and run at idle.
(2) Set scan tool (M.U.T.-III) to the data reading mode for item AD, Heated Oxygen Sensor Bank 1, Sensor 2 (right rear).
  1. Transaxle: 2nd speed
  2. Drive with wide open throttle
  3. Engine: 3,500 r/min or more
    • The output voltages should be between 0.6 and 1.0 volt.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Is the sensor operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Replace the ECM (Refer to Removal and Installation ). Then go to Step 4.
 
STEP 4. 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 - Pattern 23 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0138 set?
Retry the troubleshooting.
The inspection is complete.