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

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)

Throttle position sensor

DTC SET CONDITIONS <Range/Performance problem - high>

Logic Flow Chart

Check Conditions

Throttle position sensor output voltage is 1.0 volt or lower.
Mass airflow sensor output voltage is 4.9 volts (corresponding to an air flow rate of 295 g/sec) or lower .

Judgement Criterion

Mass airflow sensor output voltage has continued to be 3.5 volts (corresponding to an air flow rate of 89 g/sec) or higher for 2 seconds.

DTC SET CONDITIONS <Range/Performance problem - low >

Logic Flow Chart

Check Conditions

Throttle position sensor output voltage is 1.5 volts or higher.
Mass airflow sensor output voltage is 0.2 volt (corresponding to an air flow rate of 0 g/sec) or higher.
Engine speed is 1,500 r/min or more.

Judgement Criterion

Mass airflow sensor output voltage has continued to be 1.8 volts (corresponding to an air flow rate of 8 g/sec) or lower 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.
Mass airflow sensor circuit harness damage, 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

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 and harness connector A-30X at MFI relay 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 8.

STEP 3. Check for harness damage between MFI relay connector A-30X (terminal No. 2) and mass airflow sensor connector A-05 (terminal No. 2).

Q. Is the harness wire in good condition?

	Go to Step 4.

	Repair it. Then go to Step 8.

STEP 4. Check harness connector B-109 at ECM for damage.

Q. 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 the continuity at mass airflow sensor harness side connector A-05.

(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 Ω or less)

Q. Does continuity exist?

Go to Step 6.

Repair harness wire between mass airflow sensor connector A-05 (terminal No. 4) and ECM connector B-109 (terminal No. 88) because of harness damage. Then go to Step 8.

STEP 6. Check for harness damage 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 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).

Q. Is DTC P0101 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 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).

Q. Is DTC P0101 set?

	Retry the troubleshooting.

	The inspection is complete.