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DTC P014C: Linear Air-Fuel Ratio Sensor Circuit Slow Response - Rich to Lean
 
 
 
 
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
  • When the average of the difference between the response times of the rich side and the lean side of the linear air-fuel ratio sensor during the monitoring time becomes equal to or higher than the predetermined value, the DTC is set as the linear air-fuel ratio sensor deterioration.
 
 
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
  • Accelerator pedal position sensor
 
 
DTC SET CONDITIONS
Logic Flow Chart
 
 
Check Conditions
  • Engine speed is between 1,219 and 3,000 r/min.
  • Volumetric efficiency is between 25.0 and 85.0 percent.
  • Mass airflow sensor output is 9 g/sec or more.
  • Engine coolant temperature is more than 60°C (140°F).
  • Under the closed loop air/fuel control.
  • The accelerator pedal is depressed.
  • Short-term fuel trim is between -25 and +25 percent.
  • More than 3 seconds have passed after the above mentioned conditions have been met.
  • During the drive cycle, the ECM performs monitoring with the accumulated total time of 10 seconds, 3 times.
Judgment Criteria
  • The average response time ratio (to lean time/to rich time) is more than specified value.
  • The amount of compensated air/fuel ratio based on the heated oxygen sensor (rear) is out of specified amount.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • None
 
 
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.

 
 
DIAGNOSIS
Required Special Tools:
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: V.C.I.
    • MB991827: USB Cable
    • MB991910: Main Harness A
STEP 1. Test the OBD-II drive cycle.
cautionTo prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position 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 P014C set?
Replace the linear air-fuel ratio sensor. Then go to Step 2.
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 2. 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 P014C set?
Retry the troubleshooting.
The inspection is complete.