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Subaru Service and Technical Support Line Newsletter

SPECIAL EDITION
2012-Current Model Subaru Evaporative Diagnostics & Smoke Testing

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When faced with an Evaporative Emissions DTC (P0441-P0459, P2404 etc.), the first thing most
Technicians do is reach for the smoke machine to check for leaks.
This should no longer be a Technicians first step for diagnosis.
Never put pressure into the ELCM or use smoke as residual oil in the smoke can
contaminate the ELCM and cause internal components to malfunction.
Instead, the first step for diagnosis should be a forced self-test of the evaporative emission
system, recording the test results, then graphing the test to determine where the problem is.
Late model Subaru vehicles are equipped with an Electronic Leak Check Module (ELCM) in their
evaporative system. The ELCM is a very sensitive and delicate piece of electronic equipment that
has the capability of performing self-tests to inspect the systems integrity for leaks and operation.
These systems operate on vacuum, not pressure, when performing their self-test.
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CAUTION: VEHICLE SERVICING PERFORMED BY UNTRAINED PERSONS COULD
RESULT IN SERIOUS INJURY TO THOSE PERSONS OR TO OTHERS.

SUBARU OF AMERICA, INC. IS
ISO 14001 COMPLIANT

The Subaru TechTIPS newsletter is intended for use by professional Technicians ONLY. Articles are
written to inform those Technicians of conditions that may occur in some vehicles, or to provide
information that could assist in the proper servicing of the vehicle. Properly trained Technicians
have the equipment, tools, safety instructions, and know-how to do the job correctly and safely. If
a condition is described, DO NOT assume that your vehicle has or will have that condition. Impreza,
Legacy, Justy, Loyale, Outback, Forester, Subaru SVX, WRX, WRX STI, Baja, Tribeca, BRZ, XV Crosstrek
and “Quality Driven” are Registered Trademarks.

ISO 14001 is the international standard for
excellence in Environmental Management
Systems. Please recycle or dispose of automotive
products in a manner that is friendly to our
environment and in accordance with all local,
state and federal laws and regulations.

Special Edition TechTIPS

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Follow the outlined directions in this document for performing the ELCM forced self-test, then
use the diagnosis procedure found in STIS to identify where the problem is. Technicians can
graph the recorded self test and compare it to the diagnosis chart. This chart is in the General
Description tab or located at the bottom of most Evap DTC Trouble Trees in STIS. This article also
includes a reference chart, along with examples of completed graphs with a set DTC. The Subaru
smoke machine tool kit comes with the correct quick disconnect plugs to be able to block off the
disconnected lines. Below are step-by-step directions for performing the ELCM force test, saving
that test data and using it to diagnose the concern.
NOTE: For diagnosing Evaporative codes on 2011-2014 models, the following testing may not
apply. Please see TechTIPS from 3/17 and / or 10/19 for performing this testing.
NOTE: This testing does not work on STI models. Always follow the testing methods outlined in the
Service Manual for STI models.
2013MY to Current Legacy and Outback
2012MY to Current Impreza
2013MY to Current XV Crosstrek
2014MY to Current Forester
2013MY-2014MY Tribeca
2015MY to Current WRX
2013MY to Current BRZ
2019MY to Current Ascent

OVERVIEW OF EVAPORATIVE SYSTEM
•
•

The ELCM is a device installed in the evaporative system to detect leaks and blockages.
According to legal regulations, leaks of 0.02 inch or more need to be detectable.

The main components in the EVAP system:
CPC valve (purge control solenoid)
ELCM
Canister
Fuel tank
Drain filter

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OVERVIEW OF EVAPORATIVE SYSTEM

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Solenoid valve
for purge control

SUMMARY OF EVAP LEAK DIAGNOSIS
•

EVAP Leak diagnosis is conducted during soak (5~7h after engine stop).

•

The ELCM draws a vacuum in the Evaporative line and determines the leak by the level of
negative pressure.

To find a 0.02-inch leak, the ELCM measures two types of pressure:
1) Reference pressure: pressure at the occurrence of a 0.02-inch leak
2) Tank pressure: pressure in the EVAP line
While measuring pressures 1) and 2), a P code is established according to the location of the
abnormality.

Special Edition TechTIPS

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SUMMARY OF EVAP LEAK DIAGNOSIS

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The conditions needed to perform the test are as follows:
Vehicle

Model Year

Engine Coolant
Temperature

Engine Oil
Temp

Intake Air
Temp

Battery
Voltage

F°

F°

F°

F°

V

13MY - 22MY

≥ 40

< 113

≥ 40

≥ 40

≥ 10.9

Outback/
Legacy

15MY - 22MY

≥ 40

< 113

≥ 40

≥ 40

≥ 10.9

Forester

14MY - 22MY

≥ 40

< 113

≥ 40

≥ 40

≥ 10.9

Ascent

ALL

≥ 40

< 113

≥ 40

≥ 40

≥ 10.9

WRX

15MY - 22MY

≥ 40

< 113

≥ 40

≥ 40

≥ 10.9

13MY - 20MY

≥ 40

< 113

≥ 40

≥ 40

≥ 10.9

22MY

≥ 40

< 95

≥ 40

≥ 40

≥ 10.9

13MY-14MY

≥ 40

< 113

≥ 40

≥ 40

≥ 10.9

Impreza/
Crosstrek

BRZ
Tribeca

NOTE: There is no fuel level standard for test conditions other than the tank cannot be full.
The IGN must be ON with the engine OFF when performing the test. The self-test will take 15-30
minutes. Using the DCA-8000 in power supply mode is always recommended.
CAUTION: Test results may be unstable or inaccurate when fuel levels are 100%.
From the SSM4 Menu:
This test is performed with the
engine stopped and
IGNITION-ON.
Select Diagnosis
(Not Generic OBDII)

X

Choose the appropriate vehicle info.

NO

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SUMMARY OF EVAP LEAK DIAGNOSIS

(CONTINUED)

Select Each
System

Select Engine

Select Work Support
(Not Active Test)

X
NO

Select Evaporative
System Leak Test

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SUMMARY OF EVAP LEAK DIAGNOSIS

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After being asked about the
execution conditions, memory
clearing conditions, etc., press
“Start” to start Leak Test.
*Avoid using the test
immediately after refueling or
when the battery voltage is
low, as this may cause false
readings.

After the parameters have been met and the test is started,
the SSM will indicate the test is “Running”.

After confirmation that the test is running, select Combo Graph.
This will allow observation of the test in real time.

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SUMMARY OF EVAP LEAK DIAGNOSIS

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Change the items to be displayed
•

Evap System Absolute Pressure
•

ELCM switching valve
•

ELCM pump

Change time scale from “1” to “60”.

Click to adjust value scale

Choose Evap System Absolute Pressure.

Select Manual range.
Adjust Max: 43.5000 psi to 15.0000 psi
Adjust Min: 0 psi

Special Edition TechTIPS

13.5000 psi

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SUMMARY OF EVAP LEAK DIAGNOSIS

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Technicians will now be able to watch the test as it is being performed.
As the test runs, it will perform different phases.
Phase

Explaination of Phase

Phase A

The ECM uses this phase to check the operation of the vacuum pump.
The ECM simulates a 0.02 leak by using the reference pressure as the vacuum pump is running.
The switching valve is in the ‘open’ position. This allows ambient air to enter the ELCM.
Phase B

The ECM measures the pressure and calculates the limit of negative pressure based on the
reference.
Phase C

The switching valve closes, and ECM measures the evaporative side pressure. The jump in pressure
is caused by the movement of the switching valve. This also seals the system from ambient air.
Phase D

With the switching valve closed, the ECM measures the pressure in the EVAP system in relation to
the amount of time it takes to reach maximum vacuum.
Phase E

The ECM measures the reference pressure again with the 0.02 simulated leak (ELCM orifice). During
this phase, the ECM is determining the size of any leaks. Pressure during this phase is compared to
pressure during phase B and should be very similar.
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SUMMARY OF EVAP LEAK DIAGNOSIS

PhaseZ

PhaseA

PhaseD

PhaseE

PhaseB

PhaseB

PhaseE

(CONTINUED)

PhaseC

PhaseC

PhaseD

Finish

Judgement

The test can take 15-30 minutes
to complete. Once the test has
completed, the SSM will show “No
DTC” or “DTC” code is entered.

NOTE: Turbocharged vehicles will NOT set DTC P04AE after performing the self-test.
On turbocharged vehicles, after performing the ELCM self-test, without turning the key off,
perform an all DTC scan to verify there are no DTC’s set. This is a problem with the SSM4
software that will be corrected with a future software update.

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SUMMARY OF EVAP LEAK DIAGNOSIS

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This is an example of a completed self-test, with “No DTC” set after being performed:

This is an example of a completed self-test, with “P0455” set after being performed:

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SUMMARY OF EVAP LEAK DIAGNOSIS

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This is an example of a completed self-test, with “P0456” set after being performed:

This is an example of a completed self-test, with “P2404” set after being performed:
Evap System Absolute Pressure (Phase A) was not changed.

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SUMMARY OF EVAP LEAK DIAGNOSIS

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Evap System Absolute Pressure (Phase A) was too high.

Evap System Absolute Pressure (Phase A) was too low.

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SUMMARY OF EVAP LEAK DIAGNOSIS

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Above is a picture from STIS showing the basic outline for diagnosis in the ELCM force test. This will
be useful in a comparison to the data graphed from the force test if a DTC is found.

Be sure to save the file with a name.

The data of the Leak Test will be saved with the name given in the previous step.

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SUMMARY OF EVAP LEAK DIAGNOSIS

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Press Export, and a pop-up window for saving data will appear. Be sure to check the
checkboxes, as the data will be saved if they are checked.
•

Data under test (MODE$01)

•

Test result (MODE$06)

•

DTC code (MODE$02,$03,$07)

are automatically saved in the system.

Save it!

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