Lexus NX: Mass Air Flow Circuit Range / Performance Problem (P0101)

DESCRIPTION

Refer to DTC P0102.

Click here

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory
P0101	Mass Air Flow Circuit Range / Performance Problem	All of the following conditions continue for more than 10 seconds (2 trip detection logic): (a) The engine is running. (b) The engine coolant temperature is 70°C (158°F) or higher. (c) The throttle position sensor voltage is 0.2 V or higher, and less than 2 V. (d) Average engine load value ratio is less than 0.85, or higher than 1.15 (varies with estimated engine load). Average engine load value ratio = Average engine load based on mass air flow meter sub-assembly output / Average engine load estimated from driving conditions (e) Average air fuel ratio is less than -20%, or higher than 20%	Mass air flow meter sub-assembly Intake system PCV hose connections EGR valve assembly	Comes on	DTC stored

MONITOR DESCRIPTION

The mass air flow meter sub-assembly is a sensor that measures the amount of air flowing through the throttle valve. The ECM uses this information to determine fuel injection timing and to provide an appropriate air fuel ratio. Inside the mass air flow meter sub-assembly, there is a heated platinum wire which is exposed to the flow of intake air. By applying a specific electrical current to the wire, the ECM heats it to a specific temperature. The flow of incoming air cools both the wire and an internal thermistor, affecting their resistance. To maintain a constant current value, the ECM varies the voltage applied to the mass air flow meter sub-assembly. The voltage level is proportional to the airflow through the sensor, and the ECM uses it to calculate the intake air volume.

The ECM monitors the average engine load value ratio to check the mass air flow meter sub-assembly for malfunctions. The average engine load value ratio is obtained by comparing the average engine load calculated from the mass air flow meter sub-assembly output to the average engine load estimated from the driving conditions, such as the engine speed and the throttle opening angle. If the average engine load value ratio is below the threshold value, the ECM determines that the intake air volume is low, and if the average engine load value ratio is above the threshold value, the ECM determines that the intake air volume is high.

If this is detected in 2 consecutive driving cycles, the MIL is illuminated and this DTC is stored.

MONITOR STRATEGY

Related DTCs	P0101: Mass air flow meter rationality
Required Sensors/Components (Main)	Mass air flow meter sub-assembly
Required Sensors/Components (Related)	Crankshaft position sensor Camshaft position sensor Engine coolant temperature sensor Throttle position sensor
Frequency of Operation	Continuous
Duration	10 times
MIL Operation	2 driving cycles
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored	None
All of the following conditions are met	-
Throttle position voltage	0.2 V or higher, and less than 2 V
Time after engine start	5 seconds or more
Auxiliary battery voltage	10.5 V or higher
Engine coolant temperature	70°C (158°F) or higher
Estimated load	30% or higher, and less than 70%
Mass air flow meter circuit fail (P0102, P0103)	Not detected
Intake air temperature sensor circuit fail (P0112, P0113)	Not detected
Engine coolant temperature sensor circuit fail (P0115, P0117, P0118)	Not detected
Crankshaft position sensor circuit fail (P0335)	Not detected
Throttle position sensor circuit fail (P0120, P0121, P0122, P0123, P0220, P0222, P0223, P2135)	Not detected
Canister pressure sensor circuit fail (P0452, P0453)	Not detected
Leak detection pump fail (P2401, P2402)	Not detected
Evap system vent valve fail (P2419, P2420)	Not detected

TYPICAL MALFUNCTION THRESHOLDS

Both of the following conditions are met	-
Average engine load value ratio	Less than 0.85, or higher than 1.15 (varies with estimated engine load)
Average air fuel ratio	Less than -20%, or higher than 20%

CONFIRMATION DRIVING PATTERN

WIRING DIAGRAM

Refer to DTC P0102.

Click here

CAUTION / NOTICE / HINT

HINT:

Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

1.	CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0101)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read the DTCs.

Powertrain > Engine and ECT > Trouble Codes

Result	Proceed to
DTC P0101 is output	A
DTC P0101 and other DTCs are output	B

HINT:

If any DTCs other than P0101 are output, troubleshoot those DTCs first.

B

GO TO DTC CHART

A

2.	CHECK INTAKE SYSTEM

(a) Check the intake system for vacuum leaks.

Click here

OK:

No leaks from intake system.

HINT:

Perform "Inspection After Repair" after repairing or replacing the intake system.

Click here

NG

REPAIR OR REPLACE INTAKE SYSTEM

OK

3.	CHECK PCV HOSE CONNECTIONS

(a) Check the PCV hose connections.

Click here

OK:

PCV valve and hose are connected correctly and are not damaged.

NG

REPAIR OR REPLACE PCV HOSE

OK

4.	PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE EGR STEP POSITION)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Put the engine in inspection mode (maintenance mode).

Click here

Powertrain > Hybrid Control > Utility

Tester Display
Inspection Mode

(e) Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

HINT:

The A/C switch and all accessory switches should be off.

(f) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position / Primary / MAP and Throttle Idle Position.

Powertrain > Engine and ECT > Active Test

Active Test Display
Control the EGR Step Position

Data List Display
MAP
Throttle Idle Position

(g) Confirm that the Throttle Idle Position is ON and check the MAP values in the Data List while performing the Active Test.

OK:

MAP change in response to EGR step position when Throttle Idle Position is ON in Data List.

Standard:

-	EGR Step Position (Active Test)
	0 Steps	0 to 30 Steps
MAP (Data List)	(EGR valve is fully closed)	MAP value is at least +10 kPa (75 mmHg) higher than when EGR valve is fully closed

OK

GO TO STEP 6

NG

5.	INSPECT EGR VALVE ASSEMBLY

(a) Remove the EGR valve assembly.

Click here

(b) Check if the EGR valve is stuck open.

OK:

EGR valve is tightly closed.

HINT:

Perform "Inspection After Repair" after replacing the EGR valve assembly.

Click here

NG

REPLACE EGR VALVE ASSEMBLY

OK

6.	REPLACE MASS AIR FLOW METER SUB-ASSEMBLY

(a) Replace the mass air flow meter sub-assembly.

Click here

HINT:

Perform "Inspection After Repair" after replacing the mass air flow meter sub-assembly.

Click here

NEXT

7.	CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs.

Click here

Powertrain > Engine and ECT > Clear DTCs

(e) Turn the power switch off and wait for at least 30 seconds.

(f) Turn the power switch on (IG).

(g) Turn the Techstream on.

(h) Put the engine in inspection mode (maintenance mode).

Click here

Powertrain > Hybrid Control > Utility

Tester Display
Inspection Mode

(i) Start the engine and warm it up.

(j) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

(k) Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

Powertrain > Engine and ECT > Utility

Tester Display
All Readiness

(l) Input the DTC: P0101.

(m) Check the DTC judgment result.

Techstream Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

NEXT

END

READ NEXT: