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DTC P0068: Mass Airflow Sensor Plausibility
 
 
 
 
TECHNICAL DESCRIPTION
Compare the actual measurement of volumetric efficiency by a mass airflow sensor signal with volumetric efficiency estimated from a throttle position sensor (main and sub) signal.
 
 
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)
  • Throttle position sensor
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Conditions
  • The volumetric efficiency estimated by the throttle position sensor (main) subtracted from the actual volumetric efficiency is more than 0 percent.
  • The volumetric efficiency estimated by the throttle position sensor (sub) subtracted from the actual volumetric efficiency is more than 0 percent. Or, the volumetric efficiency is 60 percent or less.
  • Engine speed is 750 r/min or higher.
Judgment Criterion
  • For 0.36 second, the difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is 33 percent or more.
  • For 0.36 second, the difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (sub) is 33 percent or more.
  • For 0.36 second, the difference between the volumetric efficiency estimated by the throttle position sensor (main) and the volumetric efficiency estimated by the throttle position sensor (sub) is 8.8 percent or less.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • Estimate the throttle opening degree and the amount of intake air given by a normal sensor, and then carry out the fuel control.
  • Intake charge pressure is restricted.
 
 
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle Pattern 7 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Mass airflow sensor failed.
  • Harness damage in mass airflow sensor circuit, or connector damage.
  • Intake air system failed.
  • There is some foreign matter around mass airflow sensor failed.
  • Intake charge pressure control system failed.
  • ECM failed.
 
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
(1) Connect scan tool (M.U.T.-IIISE) to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the diagnostic trouble code other than P0068 set?
Refer to, Diagnostic Trouble Code Chart .
Go to Step 2.
 
STEP 2. Using scan tool (M.U.T.-IIISE), check data list item 10: Mass Airflow Sensor.
(1) Start the engine and run at idle.
(2) Set scan tool (M.U.T.-IIISE) to the data reading mode for item 10, Mass Airflow Sensor.
(3) Warm up the engine to normal operating temperature: 80°C to 95°C (176°F to 203°F).
  • The standard value during idling should be between 800 and 1,120 millivolts.
  • When the engine is revved, the mass airflow rate should increase according to the increase in engine speed.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the sensor operating properly?
Go to Step 3.
Refer to, DTC P0102 - Mass Airflow Circuit Low Input , DTC P0103 - Mass Airflow Circuit High Input .
 
STEP 3. Check air intake from intake hose and intake manifold.
Are there any abnormalities?
Repair it. Then go to Step 7.
Go to Step 4.
 
STEP 4. Check for foreign matter being around the mass airflow sensor.
Are there any foreign matter?
Repair it. Then go to Step 7.
Go to Step 5.
 
STEP 5. Check Intake charge pressure.
Refer to GROUP 15, On-vehicle Service - Intake Charge Pressure Check .
Are there any abnormalities?
Repair it. Then go to Step 7.
Go to Step 6.
 
STEP 6. Check the trouble symptoms.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle Pattern 7 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0068 set?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 7.
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 7. 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 7 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0068 set?
Retry the troubleshooting.
The inspection is complete.