ATTENTION:
GENERAL MANAGER

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PARTS MANAGER

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CLAIMS PERSONNEL

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IMPORTANT - All
Service Personnel
Should Read and
Initial in the boxes
provided, right.

SERVICE MANAGER

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© 2021 Subaru of America, Inc. All rights reserved.

SERVICE BULLETIN
APPLICABILITY: 2020-26MY Legacy and Outback 2.5L NA
and 2.4L DIT
2018-26MY Crosstrek
2017-26MY Impreza
2019-26MY Forester 2.5 NA

2025-26MY Forester SHEV Hybrid

2026MY Crosstek SHEV Hybrid
2014-18MY Forester 2.0L DIT
2015-26MY WRX 2.0 DIT
2019-26MY Ascent
SUBJECT:

NUMBER: 09-74-21R
DATE:

05/06/21

REVISED:

06/25/26

Cleaning Procedure for Carbon Deposit Removal to Address
Engine Misfire DTCs, Black Smoke from the Exhaust,
Lack of Power, Knocking (Ping) and / or Rough Idle Concerns

INTRODUCTION:
This bulletin provides updated parts information and a service procedure to follow for removing
accumulated carbon deposits from fuel injectors and internal engine components (e.g. intake valves
and / or manifold, and combustion chambers). Fuel quality and how the vehicle is operated are
both major contributing factors which will have a direct effect on carbon deposit accumulation.
This cleaning procedure for carbon deposit removal is recommended to address engine misfire
DTCs, black smoke from the exhaust, lack of power, knocking (ping) and / or rough idle concerns.
The procedure outlines the use of Genuine Subaru P.E.A. (Polyether Amine) Carbon Cleaner
(p.n. SOA868V9166) and the “Carbon Clean Tool” applicator tools (p.n. SOA868V9430 or
SOA868V9432) which are both available through the Subaru Chemical Program.
IMPORTANT NOTES:
•

The actual P.E.A. bottle may appear different than the black long-neck bottle shown in the
photo below.

•

When the cleaning procedure is determined to be necessary, a minimum of two bottles of the
P.E.A. carbon cleaner will be required to complete it.

•

An order quantity of 1 (one) SOA868V9166 will be shipped as a “case” of 12- 6.76 oz. bottles.

•

There are 2 different applicator tools for use with specific bottles as specified below. These

CAUTION: VEHICLE SERVICING PERFORMED BY UNTRAINED PERSONS COULD
RESULT IN SERIOUS INJURY TO THOSE PERSONS OR TO OTHERS.
Subaru Service Bulletins are intended for use by professional technicians ONLY. They
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 this
Service Bulletin applies to your vehicle, or that your vehicle will have that condition.

Subaru of America, Inc. is
ISO 14001 Compliant
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.

Continued...
Bulletin Number: 09-74-21R; Revised: 06/25/26

Page 1 of 11

tools are not interchangeable. The current long-neck bottle will be replaced with the shorter
versions soon.
•

The new (shorter) bottle contains the same amount of P.E.A. product (6.76 oz.) but utilizes the
newer version (SOA868V9432) of the applicator tool which has a shorter siphon tube designed
to work in conjunction with the new bottle.

•

Be sure to use the correct tool for the corresponding bottle style. The siphon tube on the
original (long-style) tool is approximately 7 5/8” long while the new version for use with the
shorter bottles measures 6 3/8”.

•

The end of the siphon tube on the tool should not contact the bottom of the bottle. If it does,
the old tool is being used with the new style bottle.

•

If the tool does not extract all the contents of the bottle, the new tool may have been used with
the old bottle.

•

Each retailer has been automatically shipped ONE of the new (shorter siphon tube) applicator
tools at no charge.

•

In cases where more than one (1) P.E.A. cleaning procedure is claimed, SSM4 data will be
required.

Use tool SOA868V9430
with this black, long-neck
style bottle only.

New tool SOA868V9432 is to
be used with these new shorter
clear or black bottles only.

SERVICE PROCEDURE / INFORMATION:
VERY IMPORTANT: APPENDIX A has been added to the end of this bulletin (pg. 10) and
it provides a Flow Chart for the overall Service Procedure described below. It is STRONGLY
RECOMMENDED Technicians review the Flow Chart closely to ensure their understanding of the
Service Procedure before proceeding further.
REMINDERS:
•

Customer satisfaction and retention starts with performing quality repairs.

•

ALWAYS road test the vehicle to confirm the customer’s concerns. If necessary, road test
with the customer to ensure a full understanding of the condition(s) before proceeding with the
procedure.
Continued...

Bulletin Number: 09-74-21R; Revised: 06/25/26

Page 2 of 11

•

STEP 1: Preliminary Inspection Procedure:
Step 1a) Connect the SSM4.
Step 1b) Check for any DTC(s) other than P030* (misfire). Correct any external spark
plug / ignition coil concerns, poor connection, etc. before attempting this procedure.
Remove the intake manifold assembly following all precautions and the service procedure
supplied in the applicable Service Manual. Inspect inside the runners closely along with the
cylinder head intake ports, plates and intake valves for any excessive amount of carbon /
soot accumulation. Clean any readily accessible components with carburetor / throttle plate
cleaner prior to re-assembly. Do not attempt to clean the intake valves at this point. Avoid
allowing cleaners to enter the engine. If any other concerns are found, diagnose according
to the applicable Service Manual procedure before attempting this carbon cleaning
procedure.

Note: For SHEV models perform the procedure when engine and inverter coolant is not drained.
IMPORTANT NOTES:
•

ALWAYS use new intake manifold and EGR pipe gaskets along with any other one-time use
parts as specified in the applicable Service Manual procedure during re-assembly.

•

NOTE: The P.E.A. cleaner may worsen the conditions if other concerns exist outside of
carbon / soot accumulation.
Step 1c) Road test the vehicle and perform Drive Cycle A and B according to the
applicable Service Manual. On STIS, go to Service Diagnostics and select the related
Model Year and Model of the vehicle being repaired. Select Diagnostics then go to Engine
(Diagnostics) > (Applicable Engine Type). Scroll down to Inspection Mode > Procedure
> Inspection Mode A and Inspection Mode B then follow the related driving cycle patterns
for each. Check if any DTC(s) other than P030* are set. If any other DTC(s) are found,
diagnose and repair according to the applicable Service Manual.
Step 1d) Obtain customer authorization (if the fuel tank is not already full) to fill the fuel
tank (for later P.E.A. application). NOTE: Fueling and engine oil top-off expenses cannot
be claimed.
IMPORTANT: DO NOT add P.E.A. carbon cleaner to the fuel tank before completing all
of Step 2 below.
Step 1e) Inspect the ignition coils and spark plugs closely for evidence of tracking, poor
electrical connection, etc.
Step 1f) Confirm the engine oil level is full. Top off if necessary.
Step 1g) For 2.5L DINA engines, proceed to Step 2. For Turbo and other engines, proceed
to Step 3.

•

STEP 2: Checking the Roughness Counter with SSM4 (NATURALLY ASPIRATED 2.5L
MODELS (DINA) ONLY):
IMPORTANT CAUTION: Always confirm the parking brake is fully applied and the select
lever is in the Park position (CVT models) or the shift lever is in the neutral position (MT
models).
Step 2a) With the SSM4 connected, turn the ignition to ON and access the Data Monitor.
Begin sampling data (all PIDs).
Continued...

Bulletin Number: 09-74-21R; Revised: 06/25/26

Page 3 of 11

Step 2b) Start the engine and warm it up until the radiator fan cycles on. Document any
unusual noises or concerns with the engine.
Step 2c) Turn the ignition OFF and allow the engine to cool down. The use of a
supplemental cooling fan to circulate air and cool the engine compartment is recommended.
Step 2d) Turn the ignition and SSM4 back ON (engine OFF) access the Data Monitor
again and monitor the coolant temperature until it is 60 +/- 2 deg. C (140+/- 3.6 deg. F).
Step 2e) Restart the engine, turn the A/C ON and set the system to “MAX” then allow the
engine to idle for one minute.
Step 2f) Save the SSM4 data and turn the ignition OFF.
Step 2g) Confirm the data is correctly captured as listed below:
•

Coolant temperature is 60 +/-2 deg. C (140+-3.6 F deg. F) at the start of
measurement.

•

A/C is ON at the start of measurement.

•

“Flag control of Catalyst Rapid Warming-up reflect Ignition Timing” is ON at the
start of measurement (it is OK if it changes to OFF during the measurement).

Step 2h) Read the roughness counter values on all cylinders by referring to FIG 1 below
and record the values on the Repair Order for reference later in the procedure.
•

FIG 1: How to Read the Roughness Counter:
On the SSM4, display the items listed below:
•

Flag control of Catalyst Rapid Warming-up reflect Ignition Timing

•

Misfire Monitoring (comp)

•

Engine RPM

•

Roughness Counters #1, #2, #3 and #4.

•

The roughness counter rises and resets (drops sharply) repeatedly which is the reason the
signals form triangles. Read the peak values of each triangle on all cylinders until the
“Misfire Monitoring (comp)” changes to “0” then, add all the values to get a “total” value.
A TOTAL count of 34 or less is to be considered acceptable.

If the TOTAL Roughness Counter number:
•

EXCEEDS 34, proceed to the P.E.A. cleaning procedure starting with Step 3 below.

•

Is 34 OR LESS, proceed to the Warranty and Claim Information and process a claim for
Roughness Counter Inspection Only.

Continued...
Bulletin Number: 09-74-21R; Revised: 06/25/26

Page 4 of 11

EXAMPLE 1:

EXAMPLE 2:

•

STEP 3 (all models): Pour ONE full bottle of P.E.A. carbon cleaner into the vehicle’s FULL
fuel tank. REMINDER: The fuel tank MUST be FULL.

•

STEP 4: With the valve CLOSED as shown below, remove the cap and
thread the applicator tool onto the P.E.A. bottle. During use, try to keep
the bottle vertical to insure all the contents are consumed.

Continued...
Bulletin Number: 09-74-21R; Revised: 06/25/26

Page 5 of 11

•

STEP 5: Use the hanging hook to hold the assembled
applicator tool on the hood striker as shown here.

•

STEP 6: Remove the purge hose and connect the hose from the applicator tool. Refer to the
images below for the hose locations.
2.4 DIT
FRONT

FRONT

2.0 DIT

FRONT

FRONT

Continued...
Bulletin Number: 09-74-21R; Revised: 06/25/26

Page 6 of 11

2.0L & 2.5L DINA

SHEV Hybrid Engines

•

STEP 7: Application of P.E.A. Carbon Cleaner into the Intake Manifold:

NOTE: For SHEV hybrid only, use SHEV Inspection Mode Measure Exhaust Gas to keep
the engine running, and use the accelerator pedal to maintain the desired engine speed.
With the vehicle key in the ON position and the engine OFF, enter Inspection Mode. Refer to:
DIAGNOSTICS > HYBRID POWERTRAIN CONTROL (DIAGNOSTICS) (SHEV) > Work
Support > List > Inspection Mode Measure Exhaust Gas. Once the vehicle is in Inspection
Mode, start the engine and perform the procedure below. To exit Inspection Mode, cycle the
key.
IMPORTANT CAUTION: The cleaning operation MUST be performed in well-ventilated
area. If performed inside, always confirm the vehicle is connected to an exhaust evacuation
system before proceeding.
Step 7a) Start the engine and warm it up until the radiator fan cycles on. Keep the engine
speed at 2000rpm using the SSM4.
IMPORTANT: To avoid engine overheating, keep the engine hood open. The use of a
supplemental cooling fan to circulate air and cool the engine compartment is recommended.
Continued...
Bulletin Number: 09-74-21R; Revised: 06/25/26