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DTC P0131-00: Linear A/F Sensor circuit low voltage
 
 
 
 
CIRCUIT OPERATION
The linear air-fuel ratio sensor and the ECM are connected by the following three lines to detect the air-fuel ratio.
  • The line between the linear air-fuel ratio sensor terminal number 6 and the ECM connector terminal number 54 detects the air-fuel ratio.
  • The auxiliary line between the linear air-fuel ratio sensor connector terminal number 1 and the ECM connector terminal number 53 detects the air-fuel ratio.
  • The line between the linear air-fuel ratio sensor connector terminal number 5 and the ECM connector terminal number 51 is connected to ground.
 
 
TECHNICAL DESCRIPTION
  • The ECM effects air-fuel ratio feedback control in accordance with the signals from the linear air-fuel ratio sensor.
  • If the linear air-fuel ratio sensor has deteriorated, corrections will be made by the heated oxygen sensor (rear).
 
 
DESCRIPTIONS OF MONITOR METHODS
If one of the three line voltages is excessively low or if all the three line voltages are excessively low, the DTC is set as a malfunction.
 
 
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)
  • Linear air-fuel ratio sensor heater monitor
  • Misfire monitor
  • Fuel system 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
  • Fuel tank pressure sensor
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Condition
  • 12V battery positive voltage is more than 10.0 volts and is less than 16.5 volts.
Judgment Criterions
  • Ip+ input voltage has become 1 volt or less for 3 times.
    or
  • COM+ input voltage has become 1 volt or less for 3 times.
    or
  • Vs+ input voltage has become 1 volt or less for 3 times.
 
 
FAIL-SAFE AND BACKUP FUNCTION
Does not control air-fuel ratio closed loop.
 
 
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:)
  • Linear air-fuel ratio sensor failed.
  • Shorted linear air-fuel ratio sensor circuit or connector 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
1.STEP 1. Check harness between linear air-fuel ratio sensor connector terminal number 6 and ECM connector terminal number 54.
Check signal line for short circuit.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
2.STEP 2. Check harness between linear air-fuel ratio sensor connector terminal number 1 and ECM connector terminal number 53.
Check signal line for short circuit.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
3.STEP 3. Check harness between linear air-fuel ratio sensor connector terminal number 5 and ECM connector terminal number 51.
Check ground line for short circuit.
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). Then
Repair or replace the connector, or repair the damaged harness wire.
 
4.STEP 4. 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 P0131-00 set?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
The inspection is complete.