DTC P0102: Mass Airflow Circuit Low 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 voltage which corresponds to the mass airflow rate.
The ECM checks whether the voltage output by the mass airflow sensor while the engine is running is within a specified range.

DESCRIPTIONS OF MONITOR METHODS

MONITOR EXECUTION

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

3 seconds or more have passed since the ignition switch was turned to "ON" position.

Judgement 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.

OBD-II DRIVE CYCLE PATTERN

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:

MB991958: Scan tool (M.U.T.-III Sub Assembly)

MB991824: V.C.I.
MB991827: USB Cable
MB991910: Main Harness A

MB992110: Power Plant ECU Check Harness

STEP 1. Using scan tool MB991958, check data list item 10: Mass Airflow Sensor.

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.

(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 mV.
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.

STEP 2. Check harness connector A-05 at mass airflow sensor for damage.

Q. Is the harness connector in good condition?

	Go to Step 3.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 10.

STEP 3. Measure the power supply voltage at mass airflow sensor harness side connector A-05.

(1)Disconnect the connector A-05 and measure at the harness side.
(2)Turn the ignition switch to the "ON" position.
(3)Measure the voltage between terminal No. 2 and ground.

Voltage should be battery positive voltage.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is battery positive voltage (approximately 12 volts) present?

Go to Step 5.

Go to Step 4.

STEP 4. Check harness connector A-30X at MFI relay for damage.

Q. Is the harness connector in good condition?

	Repair harness wire between MFI relay connector A-30X (terminal No. 2) and mass airflow sensor connector A-05 (terminal No. 2) because of open circuit or short circuit to ground. Then go to Step 10.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 10.

STEP 5. Check harness connector B-109 at ECM for damage.

Q. Is the harness connector in good condition?

	Go to Step 6.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 10.

STEP 6. Measure the sensor output voltage at ECM connector B-109 by using power plant ECU check harness special tool MB992110.

(1)Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.
(2)Start the engine.

(3)Measure the voltage between terminal No. 87 and ground.

When the engine is revved, voltage should be increase in response to revving.

Q. Is the measured voltage normal?

Go to Step 9.

Go to Step 7.

STEP 7. Check for open circuit or short circuit to ground between mass airflow sensor connector A-05 (terminal No. 3) and ECM connector B-109 (terminal No. 87).

Q. Is the harness wire in good condition?

	Go to Step 8.

	Repair it. Then go to Step 10.

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 23

(3)Check the diagnostic trouble code (DTC).

Q. Is DTC P0102 set?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Judgment Table <Vehicles with KOS> or GROUP 42C, Diagnosis - ID Codes Registration Judgment Table <Vehicles with WCM> . Then go to Step 10.

	The inspection is complete.

STEP 9. Using scan tool MB991958, check data list item 10: Mass Airflow Sensor.

(1)Start the engine and run at idle.
(2)Set scan tool MB991958 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 1,350 and 1,670 mV.
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.

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

Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Judgment Table <Vehicles with KOS>

or GROUP 42C, Diagnosis - ID Codes Registration Judgment Table <Vehicles with WCM>

. Then go to Step 10.

STEP 10. 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 23

(2)Check the diagnostic trouble code (DTC).

Q. Is DTC P0102 set?

	Retry the troubleshooting.

	The inspection is complete.