[Previous][Next]
DTC P0031-00: Linear A/F Sensor Heater circuit low input
 
 
 
 
CIRCUIT OPERATION
  • MFI relay is built into the IPDM E/R.
  • Power is supplied to the heater power terminal of the linear air-fuel ratio sensor connector terminal number 3 from the MFI relay connector terminal.
  • The heater of the linear air-fuel ratio sensor is controlled by the power transistor in the ECM connector terminal number 1.
 
 
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
Linear air-fuel ratio sensor heater 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 set in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Conditions
  • More than 2 seconds have passed since the power supply mode of the electric motor switch was ON.
  • While the linear air-fuel ratio sensor heater is on.
  • 12V battery positive voltage is between 11.0 and 16.5 volts.
Judgment Criterion
  • The linear air-fuel ratio sensor heater current has continued to be lower than average 0.17 ampere for 2 seconds.
Check Conditions
  • More than 2 seconds have passed since the power supply mode of the electric motor switch was ON.
  • While the linear air-fuel ratio sensor heater is off.
  • 12V battery positive voltage is between 11.0 and 16.5 volts.
Judgment Criterion
  • The linear air-fuel ratio sensor heater voltage has continued to be lower than average 2.0 volts for 2 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
None.
 
 
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function, OBD-II Drive Cycle – Pattern 1 OBD- II DRIVE CYCLE.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Open or shorted linear air-fuel ratio sensor heater circuit, harness damage or connector damage.
  • Linear air-fuel ratio sensor heater failed.
  • 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
1.STEP 1. Check linear air-fuel ratio sensor itself.
Check linear air-fuel ratio sensor itself (Refer to LINEAR AIR-FUEL RATIO SENSOR CHECK).
Q: Is the check result normal?
Replace the linear air-fuel ratio sensor (Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Exhaust Gas Purification System CATALYTIC CONVERTER REMOVAL AND INSTALLATION).
 
2.STEP 2. Perform voltage measurement at linear air-fuel ratio sensor connector terminal number 3.
  • Disconnect connector, and measure at harness side.
  • Power supply mode of electric motor switch: ON
  • Voltage between linear air-fuel ratio sensor connector terminal number 3 and ground.
OK: 12V battery positive voltage
Q: Is the check result normal?
Repair or replace the connector, or check and repair harness between linear air-fuel ratio sensor connector terminal number 3 and IPDM E/R connector terminal number 75.
 
3.STEP 3. Perform voltage measurement at ECM connector terminal number 1.
  • Disconnect connector, and measure at harness side.
  • Power supply mode of electric motor switch: ON
  • Voltage between ECM connector terminal number 1 and ground.
OK: 12V battery positive voltage
Q: Is the check result normal?
Repair or replace the connector, or check and repair harness between linear air-fuel ratio sensor connector terminal number 4 and ECM connector terminal number 1.
 
4.STEP 4. Check harness between linear air-fuel ratio sensor connector terminal number 3 and IPDM E/R connector terminal number 75.
Check power supply line for damage.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
5.STEP 5. Check harness between linear air-fuel ratio sensor connector terminal number 4 and ECM connector terminal number 1.
Check ground line for damage.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
6.STEP 6. Test the OBD-II drive cycle.
After erasing the DTC, carry out test drive with the drive cycle pattern, and recheck the DTC.
(1) Use scan tool (M.U.T.-III SE) to erase the DTC.
(2) Carry out test drive with the drive cycle pattern (Refer to Diagnostic Function, OBD-II Drive Cycle – Pattern 1 OBD- II DRIVE CYCLE).
(3) Use scan tool (M.U.T.-III SE) to recheck the DTC.
Q: Is DTC P0031-00 set?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
Intermittent malfunction (Refer to GENERAL INFORMATION, General Information – How to Use Troubleshooting/Inspection Service Points – How to Cope with Intermittent Malfunctions HOW TO COPE WITH INTERMITTENT MALFUNCTIONS).