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DTC P0102: Mass Airflow Circuit Low Input
 
 
 
 
CIRCUIT OPERATION
  • The mass airflow sensor power is supplied from the MFI relay, and the ground is provided on the ECM terminal AFSE.
  • Sensor reference voltage (5-volt voltage) is applied to the mass airflow sensor terminal from the ECM terminal AFS5.
  • A voltage that is according to the mass airflow rate is sent to the ECM terminal AFS from the mass airflow sensor output terminal.
 
 
TECHNICAL DESCRIPTION
  • The mass airflow sensor outputs current that varies in accordance with the intake air volume.
  • The ECM uses the amperage output by the mass airflow sensor and the engine speed signal in order to determine the basic injection duration of the injector.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Mass airflow sensor output voltage is out of specified range.
 
 
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)
  • Not applicable
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Condition
  • More than 3 seconds have passed since the ignition switch was turned to "ON" position.
Judgment Criterion
  • Mass airflow sensor output voltage has continued to be lower than 0.2 volt (corresponding to an air flow rate of 0 g/sec) for 2 seconds.
 
 
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 1 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
  • Mass airflow sensor failed.
  • Open or shorted mass airflow sensor circuit, or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tool:
  • MB991709: Test Harness
STEP 1. Using scan tool (M.U.T.-IIISE), check data list item 10: Mass Airflow Sensor.
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) Start the engine and run at idle.
(3) Set scan tool (M.U.T.-IIISE) 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 800 and 1,120 millivolts.
  • When the engine is revved, the mass airflow rate 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. Measure the power supply voltage at mass airflow sensor harness side connector.
(1) Disconnect the mass airflow sensor connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal power supply line and ground.
  • Voltage should be battery positive voltage.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 3.
Repair or replace the connector(s), or check and repair the harness of short to ground and open circuit in power supply line between MFI relay connector and mass airflow sensor connector. Then go to Step 9.
 
STEP 3. Measure the sensor output voltage at mass airflow sensor connector.
(1) Using test harness special tool MB991709 to connect connector, and measure at pick-up harness.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal AFS5 line and ground.
  • voltage should be between 4.9 and 5.1 volts.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the measured voltage normal?
Go to Step 5.
Go to Step 4.
 
STEP 4. Check of open circuit and short circuit to ground in AFS5 line between mass airflow sensor connector and ECM connector.
Is the harness wire in good condition?
Then go to Step 5.
Repair the connector(s) or wiring harness. Then go to Step 9.
 
STEP 5. Check of short circuit and open circuit in AFS line between mass airflow sensor connector and ECM connector.
Is the harness wire in good condition?
Go to Step 6.
Repair the connector(s) or wiring harness. Then go to Step 9.
 
STEP 6. Check of harness damage in power supply line between MFI relay connector and mass airflow sensor connector.
Is the harness wire in good condition?
Go to Step 7.
Repair the connector(s) or wiring harness. Then go to Step 9.
 
STEP 7. 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?
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 8.
 
STEP 8. 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 1 .
(3) Check the diagnostic trouble code (DTC).
Is DTC P0102 set?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 9.
The inspection is complete.
 
STEP 9. 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 P0102 set?
Retry the troubleshooting.
The inspection is complete.