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DTC P0101: Mass Airflow Circuit Range/Performance Problem

 
 
 
 
CIRCUIT OPERATION
  • The mass airflow sensor power is supplied from the MFI relay (terminal No. 2), and the ground is provided on the ECM (terminal No. 88).
  • A voltage that is according to the mass airflow rate is sent to the ECM (terminal No. 87) from the mass airflow sensor output terminal (terminal No. 3).
 
 
TECHNICAL DESCRIPTION
  • While the engine is running, the mass airflow sensor outputs electric current which corresponds to the mass airflow rate.
  • The ECM converts the electric current into the voltage and checks whether the voltage is within a specified range while the engine is running.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Compare load value with mass airflow sensor output voltage.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Throttle position sensor
 
 
DTC SET CONDITIONS <Range/Performance problem - high>
Logic Flow Chart
Check Conditions
  • Throttle position sensor output voltage is less than 0.8 volt.
  • Mass airflow sensor output voltage is less than 4.9 volts (corresponding to an air flow rate of 263 g/sec).
Judgment Criterion
  • Mass airflow sensor output voltage is more than 2.5 volts (corresponding to an air flow rate of 25 g/sec) for 2 seconds.
 
 
DTC SET CONDITIONS <Range/Performance problem - low >
Logic Flow Chart
Check Conditions
  • Throttle position sensor output voltage is more than 1.5 volts.
  • Mass airflow sensor output voltage is more than 0.2 volt (corresponding to an air flow rate of 0 g/sec).
  • Engine speed is more than 1,500 r/min.
Judgment Criterion
  • Mass airflow sensor output voltage is less than 1.8 volts (corresponding to an air flow rate of 7 g/sec) for 2 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • Fuel control is carried out using throttle opening degree and engine speed in accordance with preset map.
 
 
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 stored are:)
  • Mass airflow sensor failed.
  • Mass airflow sensor circuit harness damage, or connector damage.
  • ECM failed.
 
 
DIAGNOSIS
Required Special Tool:
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: V.C.I.
    • MB991827: USB Cable
    • MB991910: Main Harness A
STEP 1. Using scan tool MB991958, check data list item 10: Mass Airflow Sensor.
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) Start the engine and run at idle.
(3) Set scan tool MB991958 to the data reading mode for item 10, Mass Airflow Sensor.
(4) 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 1,350 and 1,670 millivolts.
  • When the engine is revved, the output voltage should increase according to the increase in engine speed.
(5) Turn the ignition switch to the "LOCK" (OFF) position.
Is the sensor operating properly?
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 .
Go to Step 2.
 
STEP 2. Check harness connector A-07 at mass airflow sensor and harness connector A-37X at MFI relay for damage.
Are the harness connectors in good condition?
Go to Step 3.
Repair or replace them. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 8.
 
STEP 3. Check for harness damage between MFI relay connector A-37X (terminal No. 2) and mass airflow sensor connector A-07 (terminal No. 1).
Is the harness wire in good condition?
Go to Step 4.
Repair it. Then go to Step 8.
 
STEP 4. Check harness connector B-27 at ECM for damage.
Is the harness connector in good condition?
Go to Step 5.
Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 8.
 
STEP 5. Check for harness damage between mass airflow sensor connector A-07 (terminal No. 3) and ECM connector B-27 (terminal No. 87).
Is the harness wire in good condition?
Go to Step 6.
Repair it. Then go to Step 8.
 
STEP 6. Check for harness damage between mass airflow sensor connector A-07 (terminal No. 4) and ECM connector B-27 (terminal No. 88).
Is the harness wire in good condition?
Go to Step 7.
Repair it. Then go to Step 8.
 
STEP 7. Replace the mass airflow sensor.
(1) Replace the mass airflow sensor.
(2) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 7 .
(3) Check the diagnostic trouble code (DTC).
Is DTC P0101 stored?
Replace the ECM (Refer to, Removal and Installation ). Then go to Step 8.
The inspection is complete.
 
STEP 8. 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 P0101 stored?
Retry the troubleshooting.
The inspection is complete.