P0031
DTC P0031: Heated Oxygen Sensor Heater Control Circuit Low (sensor 1)Heated Oxygen Sensor (Front) Heater Circuit Part 1:
Heated Oxygen Sensor (Front) Heater Circuit Part 2:
CIRCUIT OPERATION
- Power is supplied from the MFI relay (terminal No. 4) to the heated oxygen sensor (front) heater.
- The ECM
TECHNICAL DESCRIPTION
- The ECM
- The ECM
DESCRIPTIONS OF MONITOR METHODS
- The 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)
- Engine coolant temperature sensor
DTC SET CONDITIONS
Logic Flow Chart:
Logic Flow Chart
Check Conditions
- More than 2 seconds have passed since the engine starting sequence was completed.
- While the heated oxygen sensor (front) heater is on.
- Battery positive voltage is between 11 and 16.5volts.
Judgement Criterion
- The 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 heated oxygen sensor (front) heater is off.
- Battery positive voltage is between 11 and 16.5 volts.
Judgement Criterion
- The heated oxygen sensor (front) heater voltage has continued to be lower than 2.0 volts for 2 seconds.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle Pattern 2. OBD-II Drive Cycle Pattern Lists
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
- Open or shorted heated oxygen sensor (front) heater circuit, harness damage or connector damage.
- Open circuit in heated oxygen sensor (front) heater failed.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tool:
- MD998464: Test Harness
STEP 1. Check connector B-113 at the heated oxygen sensor (front) for damage.
Q: Is the connector in good condition?
YES: Go to Step 2.
NO: Repair or replace it. Then go to Step 12.
STEP 2. Check the heated oxygen sensor (front).
1. Disconnect heated oxygen sensor (front) connector B-113 and connect test harness special tool, MD998464, to the connector on the 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 degrees C (68 degrees F)]
Q: Is the measured resistance between 4.5 and 8.0 Ohms [at 20 degrees C (68 degrees F)]?
YES: Go to Step 3
NO: Replace the heated oxygen sensor (front). Then go to Step 12.
STEP 3. Measure the power supply voltage at heated oxygen sensor (front) harness side connector B-113.
1. Disconnect connector B-113 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 5.
NO: Go to Step 4.
STEP 4. Check harness connector B-12X at the MFI relay for damage.
Q: Is the harness connector in good condition?
YES: Repair harness wire between MFI relay connector B- 12X (terminal No. 4) and heated oxygen sensor (front) connector B-113 (terminal No. 1) because of open circuit or short circuit to ground. Then go to Step 12.
NO: Repair or replace it. Then go to Step 12.
STEP 5. Measure the power supply voltage at ECM connector C-119
1. Do not disconnect connector C-119
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal No. 3 and ground by backprobing.
- 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 8.
NO: Go to Step 6.
STEP 6. Check harness connector C-119 at ECM
Q: Is the harness connector in good condition?
YES: Go to Step 7.
NO: Repair or replace it. Then go to Step 12.
STEP 7. Check for open circuit and short circuit to ground between heated oxygen sensor (front) connector B-113 (terminal No. 3) and ECM connector C-119
Q: Is the harness wire in good condition?
YES: Replace the ECM or the PCM. Then go to Step 12.
NO: Repair it. Then go to Step 12.
STEP 8. Check harness connector C-119 at ECM
Q: Is the harness connector in good condition?
YES: Go to Step 9.
NO: Repair or replace it. Then go to Step 12.
STEP 9. Check for harness damage between MFI relay connector B-12X (terminal No. 4) and heated oxygen sensor (front) connector B-113 (terminal No. 1).
Q: Is the harness wire in good condition?
YES: Go to Step 10.
NO: Repair it. Then go to Step 12.
STEP 10. Check for harness damage between heated oxygen sensor (front) connector B-113 (terminal No. 3) and ECM connector C-119
Q: Is the harness wire in good condition?
YES: Go to Step 11.
NO: Repair it. Then go to Step 12.
STEP 11. Check the trouble symptoms.
1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 2 OBD-II Drive Cycle Pattern Lists
2. Check the diagnostic trouble code (DTC).
Q:Is DTC P0031 set?
YES: Replace the ECM or the PCM. Then go to Step 12.
NO: It can be assumed that this malfunction is intermittent.
STEP 12. 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 2 OBD-II Drive Cycle Pattern Lists
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0031 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.