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DTC P2237: Linear Air-Fuel Ratio Sensor Positive Current Control Circuit/Open
 
 
 
 
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 and the ECM terminal LPFL detects the air-fuel ratio.
  • The auxiliary line between the linear air-fuel ratio sensor and the ECM terminal LSFL detects the air-fuel ratio.
  • The line between the linear air-fuel ratio sensor and the ECM terminal LEFL 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 the electrical currents of the ECM line are not detected although being supplied by the ECM, the DTC is set as an open circuit.
 
 
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 starter battery positive voltage is between 10 and 16.5 volts.
  • More than 220 seconds have passed since the engine starting sequence was completed.
Judgment Criteria
  • Difference between the negative circuit voltage and the pumping circuit voltage is lower than -2.1 volts or higher than 2.3 volts for 2 seconds.
  • The pumping current is 0 milliampere for 2 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • Does not control air-fuel ratio closed loop.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnosis Function - OBD-II Drive Cycle - Pattern 1 .
 
 
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
STEP 1. Check of open circuit in LPFL line between linear air-fuel ratio sensor connector and ECM connector.
Is the harness wire in good condition?
Go to Step 2.
Repair the connector(s) or wiring harness. Then go to Step 4.
 
STEP 2. Test the OBD-II drive cycle.
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
(1) Connect scan tool (M.U.T.-IIISE). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) .
(2) Turn on the power supply mode of the electric motor switch and delete the DTC.
(3) Carry out the test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(4) Check the diagnostic trouble code (DTC).
Is DTC P2237 set?
Then go to Step 3.
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/ Inspection Service Points - How to Cope with Intermittent Malfunctions .
 
STEP 3. Replace the linear air-fuel ratio sensor.
(1) Replace the linear air-fuel ratio sensor.
(2) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(3) Check the diagnostic trouble code (DTC).
Is DTC P2237 set?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 4.
The inspection is complete.
 
STEP 4. 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 1 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P2237 set?
Retry the troubleshooting.
The inspection is complete.