[Previous][Next]
DTC P2251-00: Linear A/F Sensor COM line (open)
 
 
 
 
CIRCUIT OPERATION
The linear air-fuel ratio sensor and the ECM are connected by the following 3 lines to detect the air-fuel ratio.
  • The line between the linear air-fuel ratio sensor connector 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
The linear air-fuel ratio sensor heater or the exhaust gas heats the linear air-fuel ratio sensor to sufficiently activate the linear air-fuel ratio sensor, resulting in the small resistance. However, the DTC is set as an open circuit if the large resistance continues.
 
 
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 Conditions
  • 12V battery positive voltage is between 10.0 and 16.5 volts.
  • More than 180 seconds have passed since the engine starting sequence was completed.
Judgment Criteria
  • The sensor impedance is higher than 450 ohms for 2 seconds.
  • The reference circuit voltage is higher than 4.2 volts for 2 seconds.
  • The pumping circuit voltage is higher than 4.2 volts for 2 seconds.
 
 
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.
  • Open 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 1 and ECM connector terminal number 53.
Check signal line for open 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 6 and ECM connector terminal number 54.
Check signal line for open circuit.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
3.STEP 3. Test the OBD-II drive cycle after replace the linear air-fuel ratio sensor.
After replacing the linear air-fuel ratio sensor and erasing the DTC, carry out test drive with the drive cycle pattern, and recheck the DTC.
(1) 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) Use scan tool (M.U.T.-III SE) to erase the DTC.
(3) Carry out test drive with the drive cycle pattern (Refer to Diagnostic Function, OBD-II Drive Cycle – Pattern 1 OBD- II DRIVE CYCLE).
(4) Use scan tool (M.U.T.-III SE) to recheck the DTC.
Q: Is DTC P2251-00 set?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
The inspection is complete.