Lexus NX: Evaporative Emission Control System Incorrect Purge Flow (P0441)

Lexus NX Service Manual / Engine & Hybrid System / 2ar-fxe (engine Control) / Sfi System / Evaporative Emission Control System Incorrect Purge Flow (P0441)

DTC SUMMARY

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory
P0441	Evaporative Emission Control System Incorrect Purge Flow	One of the following conditions met: Leak detection pump creates negative pressure (vacuum) in EVAP system and EVAP system pressure measured. Reference pressure is measured at start and at end of leak check. If stabilized pressure higher than [second reference pressure x 0.2], ECM determines that purge VSV stuck open. After EVAP leak check performed, purge VSV turned on (open), and atmospheric air introduced into EVAP system. Reference pressure is measured at start and at end of check. If pressure does not return to near atmospheric pressure, ECM determines that purge VSV stuck closed. While engine running, following conditions successively met: Negative pressure not created in EVAP system when purge VSV turned on (open) EVAP system pressure change less than 0.5 kPa(gauge) [3.75 mmHg(gauge)] when vent valve turned on (closed) Atmospheric pressure change before and after purge flow monitor less than 0.1 kPa(gauge) [0.75 mmHg(gauge)]	Purge VSV Purge line Connector/wire harness (Purge VSV - ECM) ECM Canister pump module Canister (filter inside canister clogged) Leak from EVAP system	Comes on	DTC stored

DTC No.	Monitoring Item	Detection Timing	Detection Logic
P0441	Purge VSV (Vacuum Switching Valve) stuck open	While power switch off	2 trip
	Purge VSV stuck closed	While power switch off	2 trip
	Purge flow	While engine running	2 trip

DESCRIPTION

The description can be found in EVAP (Evaporative Emission) System.

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MONITOR DESCRIPTION

The 2 monitors, Key-Off and purge flow, are used to detect malfunctions relating to DTC P0441. The Key-Off monitor is initiated by the ECM internal timer, known as the soak timer, 5 hours after the power switch is turned off. The purge flow monitor runs while the engine is running.

KEY-OFF MONITOR

5 hours* after the power switch is turned off, the electric leak detection pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.

HINT:

*: If the engine coolant temperature is not less than 35°C (95°F) 5 hours after the power switch is turned off, the monitor check starts 2 hours later. If it is still not less than 35°C (95°F) 7 hours after the power switch is turned off, the monitor check starts 2.5 hours later.

Sequence	Operation	Description	Duration
-	ECM activation	Activated by soak timer 5, 7 or 9.5 hours after power switch turned off.	-
A	Atmospheric pressure measurement	Vent valve is turned off (vent) and EVAP system pressure is measured by ECM in order to register atmospheric pressure. If pressure in EVAP system is not between 70 kPa(abs) and 111 kPa(abs) [525 mmHg(abs) and 836 mmHg(abs)], ECM cancels EVAP system monitor.	60 seconds
B	First reference pressure measurement	In order to determine reference pressure, leak detection pump creates negative pressure (vacuum) through reference orifice and then ECM checks if leak detection pump and vent valve operate normally.	360 seconds
C	EVAP system pressure measurement	Vent valve is turned on (closed) to shut EVAP system. Negative pressure (vacuum) is created in EVAP system, and EVAP system pressure is then measured. Write down measured value as it will be used in leak check. If EVAP pressure does not stabilize within 15 minutes, ECM cancels EVAP system monitor.	15 minutes*
D	Purge VSV monitor	Purge VSV opened and then EVAP system pressure is measured by ECM. A large increase indicates normality.	10 seconds
E	Second reference pressure measurement	After second reference pressure measurement, leak check is performed by comparing first and second reference pressure measurements. If stabilized system pressure is higher than second reference pressure, ECM determines that EVAP system leaking.	60 seconds
-	Final check	Atmospheric pressure is measured and then monitoring result is recorded by ECM.	-

*: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

*1	Purge VSV: Off (Closed)	*2	Purge VSV: On (Open)
*3	Vent Valve: Off (Vent)	*4	Vent Valve: On (Closed)
*5	Leak Detection Pump: Off	*6	Leak Detection Pump: On
*7	Reference Orifice (0.02 inch)	*8	Canister Pressure Sensor
*9	Canister	*10	Fuel Tank
*11	Canister Pump Module	*12	Canister Filter
*a	Operation A: Atmospheric Pressure Measurement	*b	Operation B, E: Reference Pressure Measurement
*c	Operation C: EVAP System Pressure Measurement	*d	Operation D: Purge VSV Monitor
*e	Atmospheric Pressure	*f	Negative Pressure

Purge VSV stuck open
In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) system. The EVAP system pressure is then measured by the ECM using the canister pressure sensor. If the stabilized system pressure is higher than [second reference pressure x 0.2], the ECM interprets this as the purge VSV being stuck open. If any deterioration has occurred, the ECM will illuminate the MIL and store this DTC (2 trip detection logic).
Purge VSV stuck closed
In operation D, the canister pressure sensor measures the EVAP (Evaporative Emission) system pressure. The pressure measurement for the purge VSV monitor begins when the purge VSV is turned on (open) after the EVAP leak check. When the measured pressure indicates an increase of 0.3 kPa(gauge) [2.25 mmHg(gauge)] or higher, the purge VSV is functioning normally. If the pressure does not increase, the ECM interprets this as the purge VSV being stuck closed, illuminates the MIL and stores this DTC (2 trip detection logic).

PURGE FLOW MONITOR
The purge flow monitor consists of 2 monitors. The 1st monitor is conducted every time and the 2nd monitor is activated if necessary.

The 1st monitor
While the engine is running and the purge VSV is on (open), the ECM monitors the purge flow by measuring the EVAP pressure change. If negative pressure is not created, the ECM begins the 2nd monitor.
The 2nd monitor
The vent valve is turned on (closed) and the EVAP pressure is then measured. If the variation in the pressure is less than 0.5 kPa(gauge) [3.75 mmHg(gauge)], the ECM interprets this as the purge VSV being stuck closed, illuminates the MIL and stores DTC P0441 (2 trip detection logic).

Atmospheric pressure check:

In order to ensure reliable malfunction detection, the variation between the atmospheric pressures, before and after conduction of the purge flow monitor, is measured by the ECM.

MONITOR STRATEGY

Required Sensors/Components (Main)	Purge VSV Canister pump module
Required Sensors/Components (Related)	-
Frequency of Operation	Once per driving cycle
Duration	Within 20 minutes: Purge VSV stuck open/close Less than 30 seconds: Purge flow
MIL Operation	2 driving cycles
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

All

Monitor runs whenever the following DTCs are not stored

None

Key-off Monitor

Atmospheric pressure	70 kPa(abs) [525 mmHg(abs)] or higher, and less than 111 kPa(abs) [836 mmHg(abs)]
Auxiliary battery voltage	10.5 V or higher
Vehicle speed	Less than 4 km/h (2.5 mph)
Power switch	Off
Time after key-off	5, 7 or 9.5 hours
Canister pressure sensor malfunction (P0452, P0453)	Not detected
Purge VSV	Not operated by scan tool
Vent valve	Not operated by scan tool
Leak detection pump	Not operated by scan tool
Both of the following conditions met before key-off	Conditions 1 and 2
1. Duration that vehicle is driven	5 minutes or more
2. EVAP purge operation	Performed
Engine coolant temperature	4.4°C (40°F) or higher, and less than 35°C (95°F)
Intake air temperature	4.4°C (40°F) or higher, and less than 35°C (95°F)

Purge Flow Monitor

Engine	Running
Engine coolant temperature	4.4°C (40°F) or higher
Intake air temperature	4.4°C (40°F) or higher
Canister pressure sensor malfunction	Not detected
Purge VSV	Not operated by scan tool
EVAP system check	Not operated by scan tool
Atmospheric pressure	70 kPa(abs) [525 mmHg(abs)] or higher, and less than 111 kPa(abs) [836 mmHg(abs)]
Auxiliary battery voltage	10 V or higher (intake air temperature less than 50°C (122°F)) 12 V or higher (intake air temperature 50°C (122°F) or higher)
Purge duty-cycle	8% or higher

TYPICAL MALFUNCTION THRESHOLDS

Purge VSV Stuck Open

EVAP pressure when vacuum introduction is complete

Higher than [reference pressure x 0.2]

Purge VSV Stuck Closed

EVAP pressure change after purge VSV is open

Less than 0.3 kPa(gauge) [2.25 mmHg(gauge)]

Purge Flow

Both of the following conditions are met	-
EVAP pressure change when purge flow is started	Less than 0.1 kPa(gauge) [0.75 mmHg(gauge)]
EVAP pressure change during purge flow when vent valve is on (closed)	Less than 0.5 kPa(gauge) [3.75 mmHg(gauge)]

MONITOR RESULT

Refer to EVAP System.

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CONFIRMATION DRIVING PATTERN

Connect the Techstream to the DLC3.
Turn the power switch on (IG) and turn the Techstream on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the power switch off and wait for at least 30 seconds.
Turn the power switch on (IG) and turn the Techstream on.
Put the engine in inspection mode (maintenance mode).
Click here
Start the engine and wait 15 minutes or more.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
Read the pending DTCs.
HINT:
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTC: P0441.

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 You should 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

HINT:

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A, perform the following procedure.

NOTICE:

The Evaporative System Check (Automatic Mode) consists of 6 steps performed automatically by the Techstream. It takes a maximum of approximately 24 minutes.
Do not perform the Evaporative System Check when the fuel tank is more than 85% full because the cut-off valve may be closed, making the fuel tank leak check unavailable.
Do not run the engine during this operation.
When the temperature of the fuel is 35°C (95°F) or higher, a large amount of vapor forms and any check results become inaccurate. When performing the Evaporative System Check, keep the fuel temperature less than 35°C (95°F).

Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the power switch off and wait for at least 30 seconds.
Turn the power switch on (IG) and turn the Techstream on.
Enter the following menus: Powertrain / Engine and ECT / Utility / Evaporative System Check / Automatic Mode.
After the Evaporative System Check is completed, check for All Readiness by entering the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTC: P0441.

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

HINT:

If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.

If the judgment result is INCOMPLETE or N/A and no pending DTC is output, perform a universal trip and check for permanent DTCs.
Click here
HINT:
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.

PROCEDURE

1.	GO TO EVAP SYSTEM

(a) Refer to EVAP System.

Click here

END

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