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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
  • 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
  • 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 stored 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 is less than 0.2 volt (corresponding to an air flow rate of 0 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 22 .
 
 
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 Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Using scan tool (M.U.T.-III), check data list item 10: Mass Airflow Sensor.
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(1) Connect scan tool (M.U.T.-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(2) Start the engine and run at idle.
(3) Set scan tool (M.U.T.-III) 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 760 and 1,080 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. 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 open circuit and short to ground in power supply line between MFI relay connector and mass airflow sensor connector. Then go to Step 9.
 
STEP 3. Measure the sensor 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 AFS5 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 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?
Replace the ECM (Refer to, Removal and Installation ). Then go to Step 9.
Repair the connector(s) or wiring harness. Then go to Step 9.
 
STEP 5. Measure the sensor output voltage at ECM by backprobing.
(1) Do not disconnect the connector.
(2) Start the engine.
(3) Measure the voltage between terminal AFS and ground by backprobing.
  • When the engine is revved, voltage should be increase in response to revving.
Is the measured voltage normal?
Go to Step 8.
Go to Step 6.
 
STEP 6. Check of open circuit and short circuit to ground in AFS line between mass airflow sensor connector and ECM 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. 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 22 .
(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 8. Using scan tool (M.U.T.-III), check data list item 10: Mass Airflow Sensor.
(1) Start the engine and run at idle.
(2) Set scan tool (M.U.T.-III) 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 760 and 1,080 millivolts.
  • When the engine is revved, the output voltage 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 .
Replace the ECM (Refer to, Removal and Installation ). Then go to Step 9.
 
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 22 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0102 set?
Retry the troubleshooting.
The inspection is complete.