ATTENTION:
GENERAL MANAGER

q

PARTS MANAGER

q

CLAIMS PERSONNEL

q

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

SERVICE MANAGER

q

© 2023 Subaru of America, Inc. All rights reserved.

SERVICE BULLETIN
APPLICABILITY:

All Telematics Equipped Models
Except Solterra

NUMBER: 15-308-23

SUBJECT:

Diagnostic Information - Testing Telematics
Systems for Dark/Standby Current

DATE:

04/27/23

INTRODUCTION:
This Service Information Bulletin announces important diagnostic information to utilize when the
Data Communication Module (DCM) is being tested as a dark current/standby current source. When
a DCM is the suspected root cause of an excessive dark/standby current draw, the coverage, and
the signal strength PID are verified prior to the DCM being condemned. The DCM is constantly
searching for a network to attach to when it first starts or is in an area of poor coverage. If an
excessive DCM dark/standby current draw is confirmed, it is necessary also to ensure signal strength
is approximately 23% or greater. In cases where signal strength is close to or at zero and DCM
dark/standby draw is suspected, moving the car to an area with better coverage would be helpful
with confirmation and duplication of test results. On vehicles with a subscribed or unsubscribed
subscription status, a non-varying signal strength of 0% is a problem. Efforts should be made to
ensure the Telematics system is working within the expected parameters. The presence of Telematics
DTCs, a compromised primary antenna, or a non-communicating DCM should be addressed
accordingly. When a DTC is current, or the antenna path is compromised, DCM replacement may not
repair the parasitic draw. A customer interview will be valuable to aid in diagnosis. Vehicles that park
in areas of a low signal strength may experience an excessive DCM dark/standby draw, for example,
when parked in an underground parking lot but not while at the retailer. Understanding where the
customer parks their car is beneficial in understanding how the DCM may contribute to battery load
and state of charge. It is always important to inform the customer what outcome these scenarios may
cause. The low signal will cause the DCM to always be awake and seeking a network connection for
up to 14 days until the DCM hibernates.
DIAGNOSTIC INFORMATION:
Dark current or standby current is any electrical current used with the ignition turned off to maintain
volatile memory in modules, maintain clock time, and await the approach or press of a key fob
button. An excessive amount of current drain on the battery will cause it to discharge and may lead to
a no-start condition.
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: 15-308-23; Date: 04/27/23

Page 1 of 6

The DCM MUST be clear of all Telematics DTCs before starting diagnosis for dark/standby current
draw. The presence of any DTC in the DCM will skew diagnostic test results as DCM behavior
differs when DTCs are current. The DCM will consume more power and delay powering down until
all DTCs have been cleared.
CRITICAL: DCM voltage draws pulses between periods of low and higher usage as it attempts
a connection to the network. This pulsation MUST NOT be mistaken as dark/standby draw. When
looking for DCM dark/standby current draw, a non-oscillating pull of higher than expected current.
Using a DVOM with a graph function is the preferred method to identify this pulsation behavior
and calculate the average dark/standby current draw. Refer to the figure below for reference to DCM
pulsation characteristics. If there is doubt the total dark/standby current draw is caused solely by
the DCM, isolate testing to just the DCM to determine how much the DCM contributes to the entire
vehicle dark/standby current draw.
The DCM has six possible states of amperage current waveform patterns. The DCM will shut down
after a 15-day time period without the ignition being turned on. During Factory Mode (*) the DCM
will shut down after approximately 30 seconds. When the DCM cannot receive a radio wave signal,
it will attempt to find a signal once a minute causing an increase in current draw (detailed in red
below).

PREPARATION AND MEASUREMENT OVERVIEW:
Through dark/standby draw testing, determine the source of the draw following the procedure below.
If it is determined the root cause of the dark/standby draw is the DCM, it must be replaced to repair
the draw in the Telematics system.
1. Prepare the DVOM with capability to measure down to 1mA.
NOTE: The battery health state can influence the dark/standby current test results. Determining the
battery condition prior to testing can be vital. Additional battery testing and charging information can
be found in TSB 07-178-21R.
2. Remove or disconnect any aftermarket electrical accessories. This includes cameras, nonSubaru remote start equipment, insurance trackers, etc. Always check all USB ports for
connected devices.
Continued...
Bulletin Number: 15-308-23; Date: 04/27/23

Page 2 of 6

3. Start the engine and set the switch positions for each system as shown in the table below.

4. Turn the ignition switch to OFF.
5. Operate the front hood lock release lever to unlock the front hood.
6. Close all the doors (including the rear gate and trunk lid) then lock the doors. (Security alarm
is in set condition)
7. Wait at least 55 minutes before continuing for the most accurate test results. Performing
this step is CRITICAL.
8. Measure the amount of current drawn from the battery.
NOTES:
•

ALWAYS store the access key fob at least 15 feet away from the vehicle after the doors
are locked. The access key fob MUST NOT be stored adjacent to the vehicle during dark/
standby current testing.

•

The Electronic Power Steering System (EPS) may still be active 55 minutes after turning the
ignition switch to the OFF position.

•

For a model with a keyless access function, the dark/standby current can change periodically
because the keyless access system is continuously searching for the access key (polling).

•

When measuring the standby current with a graphing DVOM, the reading may oscillate.
Read the average value (median value).

•

The standby current may become significant when the vehicle system (ELCM) is activated
five times at 30-minute intervals or 5 hours after turning the ignition switch to OFF. The
measurement should be completed in 20 minutes. If it takes more than 20 minutes, start the
engine once, stop the engine, then perform the inspection.

Continued...
Bulletin Number: 15-308-23; Date: 04/27/23

Page 3 of 6

TEST RESULTS:
If the maximum measurement value is less than 70mA Standby current is normal.
If the maximum measurement value is 70mA or more, Perform the following steps.
1. If excessive current draw is recorded, remove all fuses one by one to identify which system
changes the standby current value significantly.
2. The chart below lists the fuses feeding the Telematics system. If removing one of these fuses
causes the dark/standby draw to move from a reading greater than 70mA to a value less than 70
mA, DCM replacement would be indicated.
IMPORTANT: If removal of the fuses below does not adjust DVOM readings below 70 mA, the
DCM IS NOT the root cause of the dark/standby draw and replacement is not required.

3. Check related parts, harnesses, and connectors of the system whose standby current has
changed significantly. A component left on or stuck on, shorts to power, and shorts to ground
can cause an excessive dark current draw.
SERVICE PROCEDURE / INFORMATION:
•

The work procedure for dark/standby current has not changed. Refer to the applicable vehicle
Service Manual: STARTING/CHARGING SYSTEMS > Battery

•

MY 20-22 Legacy/Outback refer to TechTip May 2022 pg. 3 section 1: Replacement
components on the CAN network and Central Gateway Control module LAN registration.

•

All Models and Years refer to TechTip April 2022, pg. 7 section 15: The Telematics LED:
When green does not mean GO.

•

All Models and Years refer to TechTip Sept. 2019, pg. 5 section 15: Telematics RES feature
inoperative and revised B2A16 diagnostics.

•

For all Models and Years with currently active STARLINK Subscription, refer to TSB
15-266-20R for minimum testing requirements post DCM replacement.

•

MY 20-21 Legacy/Outback, MY19-21 Forester, MY19-21 Ascent refer to TSB 07-199-21R.

WARRANTY / CLAIM INFORMATION:
There have been no changes made to the Labor Time Guide for these procedures.
Continued...
Bulletin Number: 15-308-23; Date: 04/27/23

Page 4 of 6

APPENDIX A: Alternate Dark Current/Standby Current Draw Test Procedure
Old Technique vs New Technique
The traditional method detailed in the body of this TSB – disconnecting the battery, putting the
multimeter in series, and pulling fuses until the draw source is found – is the method detailed in STIS
but may not always be the most efficient method of finding dark/standby draw. This inefficiency is
because the very disconnection of the battery may temporarily fix the issue by sending the system to
sleep along with the error or having to wait an excessive time for the module to go back to sleep. This
behavior can complicate isolation testing and make recorded results confusing.
An alternative diagnostic method of dark/standby current draw testing can be performed by
measuring the voltage drop across the fuses. This can be done by using the test points on the fuses
without breaking the battery connection, pulling fuses, disturbing the circuit, or awakening any
modules. What you are looking for is a voltage drop in the millivolts range. This is caused by an
increase in resistance brought about by heating the fuse through the movement of current.
Different sized fuses will show different voltage drops. For example, a 10A fuse with 175 mA flowing
through it will show a voltage drop of 1.5mV. When measuring the same fuse with no current flow, it
would be more like 0.1mV or 0.2mV.
While using this dark/standby draw isolation method, excessive mV readings indicate the need for
further root cause isolation. Disconnecting components fed by the fuse until mV readings come
within expected tolerances.

Continued...
Bulletin Number: 15-308-23; Date: 04/27/23

Page 5 of 6

Bulletin Number: 15-308-23; Date: 04/27/23

Page 6 of 6