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DTC P0103: Mass
Airflow Circuit High Input
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
Mass airflow sensor output voltage is out of specified range.
MONITOR EXECUTION
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory
for the item monitored below)
Sensor (The sensor below is determined to be normal)
DTC SET CONDITIONS
Logic Flow Chart
Check Condition
- More than 3 seconds have passed since the ignition switch was turned to "ON" position.
Judgement Criterion
- Mass airflow sensor output voltage is more than 4.9 volts (corresponding to an air
flow rate of 387 g/sec) for 2 seconds.
FAIL-SAFE AND BACKUP FUNCTION
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function -
OBD-II Drive Cycle -
Pattern
23 
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TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Mass airflow sensor failed.
- Open mass airflow sensor circuit, or connector damage.
- ECM failed.
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Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
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STEP 1. Using scan tool MB991958, check data list item
10: Mass Airflow Sensor.
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| caution |
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK"
(OFF) position before connecting or disconnecting scan tool MB991958.
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(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 1,300
and 1,650 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.
Q.
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.
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STEP 2. Check harness connector A-05 at mass airflow sensor for damage.
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Q.
Is the harness connector in good condition?
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Go to Step 3.
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Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection .
Then go to Step 8.
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STEP 3. Check the continuity at mass airflow sensor harness side connector
A-05.
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(1)Disconnect the connector A-05 and measure at the harness side.
(2)Check for the continuity between terminal No. 4 and ground.
- Continuity (2 ohms or less)
Q.
Does continuity exist?
Go to Step 7.
Go to Step 4.
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STEP 4. Check harness connector B-109 at ECM for damage.
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Q.
Is the harness connector in good condition?
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Go to Step 5.
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Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection .
Then go to Step 8.
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STEP 5. Check for open circuit between mass airflow sensor connector
A-05 (terminal No. 4) and ECM connector B-109 (terminal No. 88).
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Q.
Is the harness wire in good condition?
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Go to Step 6.
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Repair it. Then go to Step 8.
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STEP 6. Using scan tool MB991958, check data list item 10: Mass Airflow
Sensor.
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(1)Start the engine and run at idle.
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(2)Set scan tool MB991958 to the data reading mode for item 10, Mass Airflow Sensor.
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(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 1,300
and 1,650 millivolts.
- When the engine is revved, the mass airflow rate should increase according to the
increase in engine speed.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is the sensor operating properly?
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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 .
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Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP
42B, Diagnosis -
ID Code Registration Necessity Judgment Table <Vehicles with KOS> or
GROUP 42C, Diagnosis -
ID Codes Registration Judgment Table <Vehicles with WCM> .
Then go to Step 8.
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STEP 7. Check harness connector B-109 at ECM for damage.
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Q.
Is the harness connector in good condition?
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Replace the mass airflow sensor. Then go to Step 8.
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Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection .
Then go to Step 8.
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STEP 8. Test the OBD-II drive cycle.
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(1)Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function -
OBD-II
Drive Cycle -
Pattern 23 .
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(2)Check the diagnostic trouble code (DTC).
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Retry the troubleshooting.
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The inspection is complete.
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