P0031
DTC P0031: Heated Oxygen Sensor Heater Circuit Low (Bank 1, Sensor 1)Right Bank Heated Oxygen Sensor (Front) Heater Circuit (Part 1):
Right Bank Heated Oxygen Sensor (Front) Heater Circuit (Part 2):
CIRCUIT OPERATION
- Power is supplied from the MFI relay (terminal No. 2) to the right bank heated oxygen sensor (front) heater.
- The ECM (terminal No. 33) controls continuity to the right bank heated oxygen sensor (front) heater by turning the power transistor in the PCM "ON" and "OFF".
TECHNICAL DESCRIPTION
- The ECM checks whether the heater current is within a specified range when the heater is energized.
- The ECM checks whether the heater voltage is within a specified range when the heater is not energized.
DESCRIPTIONS OF MONITOR METHODS
Right bank heated oxygen sensor heater (front) current or voltage is out of 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)
- Not applicable
DTC SET CONDITION
Logic Flow Chart:
Check Conditions
- More than 2 seconds have passed since the engine starting sequence was completed.
- While the right bank heated oxygen sensor (front) heater is on.
- Battery positive voltage is between 11 and 16.5 volts.
Judgement Criterion
- The right bank heated oxygen sensor (front) heater current has continued to be lower than 0.17 ampere for 2 seconds.
Check Conditions
- More than 2 seconds have passed since the engine starting sequence was completed.
- While the right bank heated oxygen sensor (front) heater is off.
- Battery positive voltage is between 11 and 16.5 volts.
Judgement Criterion
- The right bank heated oxygen sensor (front) heater voltage has continued to be lower than 2.0 voltage for 2 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to MFI Diagnostic Function-OBD-II Drive Cycle - Pattern 2. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Connector damage.
- Right bank heated oxygen sensor (front) heater.
- Harness damage
- ECM failed.
DIAGNOSIS
Required Special Tools:
- MB991316: Test Harness
STEP 1. Check harness connector B-03 at the right bank heated oxygen sensor (front) and harness connector B-10 at the ECM for damage.
Q: Is the harness connector in good condition?
YES : Go to Step 2.
NO : Repair or replace it. Refer to General (Electrical), Harness Connector Inspection. Then go to Step 6.
STEP 2. Check the right bank heated oxygen sensor (front).
1. Disconnect right bank heated oxygen sensor (front) connector B-03 and connect test harness special tool, MB991316, to the connector on the right bank heated oxygen (front) sensor side.
2. Measure the resistance between heated oxygen sensor connector terminal No. 1 (red clip) and terminal No. 3 (blue clip).
Standard value: 4.5 - 8.0 ohms [at 20 °C (68 °F)]
Q: Is the measured resistance between 4.5 and 8.0 ohms [at 20 °C (68 °F)]?
YES : Go to Step 3.
NO : Replace the right bank heated oxygen sensor (front). Then go to Step 6.
STEP 3. Measure the power supply voltage at right bank heated oxygen sensor (front) and harness side connector B-03.
1. Disconnect the connector B-03 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 1 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is battery positive voltage (approximately 12 volts) present?
YES : Go to Step 4.
NO : Repair harness wire between the MFI relay connector A-33X (terminal No. 2) and the right bank heated oxygen sensor (front) connector B-03 (terminal No. 1) because of open circuit or harness damage. Then go to step 6.
STEP 4. Check for open circuit to ground or harness damage between right bank heated oxygen sensor (front) connector B-03 and ECM connector B-10.
1. Disconnect the right bank heated oxygen sensor (front) connector B-03 and the ECM connector B-10.
2. Measure the resistance between the heated oxygen sensor connector B-03 (terminal No. 3) and the ECM connector B-10 (terminal No. 33).
- Should be less than 2 ohms.
3. Check for the continuity between the oxygen sensor connector B-03 (terminal No. 3) and ground.
- Not continuity.
Q: Is the harness wire in good condition?
YES : Go to Step 5.
NO : Repair it. Then go to Step 6.
STEP 5. Check the trouble symptoms.
1. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function - OBD-II Drive Cycle - Pattern 2. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0031 set?
YES : Replace the ECM. When the ECM is replaced, register the ID code. Refer to Diagnosis-ID Codes Registration Judgment Table [Vehicles with KOS] or Diagnosis-ID Codes Registration Judgment Table [Vehicles with WCM]. Then go to Step 6.
NO : It can be assumed that this malfunction is intermittent. Refer to General (Body and Chassis), How to Use Troubleshooting/Inspection Service Points -How to Cope with Intermittent Malfunctions.
STEP 6. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function - OBD-II Drive Cycle - Pattern 2. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0031 set?
YES : Retry the troubleshooting.
NO : The inspection is complete.