Measurement of “Dark Current” (Parasitic Battery Draw) – Subaru

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Service Information Number: 07-85-14; Date: 06/09/14 Page 1
INTRODUCTION
This bulletin will provide the proper procedure for measuring Dark Current (parasitic battery draw)
along with the specification for maximum allowable limits. Customer concerns of batteries going
dead over a period of time should be diagnosed using this procedure once any obvious contributing
factors have been eliminated.
SERVICE PROCEDURE / INFORMATION
1- Vehicle Preparation
• Before beginning this procedure, the vehicle’s battery must be fully charged and in peak
operating condition. If needed, charge the battery fully using the MidTronics GR8 or replace
it if your diagnosis determines necessary. A battery in poor condition or in need of charge
will likely have an adverse effect on the accuracy of the dark current draw test results.
• The battery posts and cable ends must be free of corrosion, dirt, sealer and in good condition.
• Be sure to record the customer’s radio station pre-sets and navigation system favorites (if
applicable) as they will be lost during the test along with any seat memory settings. DO
NOT use an aftermarket 9-volt memory retention device in the power outlet to retain any
ECU memory.
• Disconnect or remove any aftermarket (non-OEM) electrical accessories or equipment.
• Install the back-up power supply fuse then, (if applicable) using the SSMIII, confirm the
Body Integrated Unit (BIU) is set “Market Mode”.
• Using a short piece of wire, make a jumper lead to connect to the negative battery post as
shown in the photo sequence below. Once in place and twisted tightly around the battery
post, reconnect the negative battery cable. (16 ga. wire was used for this bulletin.)
NUMBER: 07-85-14
DATE: 06/09/14
APPLICABILITY: All Models
SUBJECT: Measurement of “Dark Current”
(Parasitic Battery Draw)
SERVICE INFORMATION
ATTENTION:
GENERAL MANAGER q
PARTS MANAGER q
CLAIMS PERSONNEL q
SERVICE MANAGER q
IMPORTANT – All
Service Personnel
Should Read and
Initial in the boxes
provided, right.
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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.
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excellence in Environmental Management
Systems. Please recycle or dispose of
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Service Information Number: 07-85-14; Date: 06/09/14 Page 2
• Leaving the hood open, start the engine then position all the electrical switches as specified in
the chart below.
Electrical System Control Switch Position
Headlights ON or AUTO
Fog lights (if equipped) ON
Wipers (Front and Rear) On or Low Speed
Audio and Navigation system (OEM) ON
Rear window defogger ON
Dome light Door
Cargo area light Door
Map light OFF
Air conditioner (Auto models) ON (AUTO)
Air conditioner (Manual models) ON (Speed 1)
EPB (Electric Parking Brake) ON
All other electric components
(except those items specified above). OFF
• After all the switches have been set according to the chart, shut off the engine and remove the
ignition key.
• Leaving the hood open, exit the vehicle, making sure all the doors (including the rear gate if
equipped) are fully closed. Lock all the doors and confirm all interior lights go off.
• On push-start vehicles, the smart key (remote) will need to be at least 10 feet away to allow
the system to “go to sleep”. The smart key must remain away from the vehicle until
testing has been completed.
• From this point, allow 5 minutes for the electrical system to stabilize (“go to sleep”) before
proceeding with the actual dark current testing.
IMPORTANT:
The “window” for performing this test is only 20 minutes from the time the vehicle goes to sleep.
After approximately 20 minutes, the ELCM (if equipped) testing begins and will have an effect on
your test results. Another option is to wait approximately 5 hours after vehicle shut-down to perform
the test. This will allow plenty of time for ELCM testing to complete and eliminates the 20-minute
“window”.
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Service Information Number: 07-85-14; Date: 06/09/14 Page 3
2- Test Procedure
• Loosen the nut securing (but do not remove) the negative (-) battery cable to the battery post.
• Connect the positive (+) probe of your ammeter to the negative (-) battery cable terminal end.
• Connect the negative (-) probe of the ammeter to the exposed end of the jumper wire.
On vehicles with a battery sensor on the negative battery terminal, leave the terminal connected
and connect a jumper lead to the bus bar area between the terminal end and the 12mm nut as shown
below for the feed to the DVOM. Once the DVOM is connected, remove the 12mm nut, the battery
cable from the stud then perform the test. After testing, re-torque the nut to 7.5 Nm (5.5 ft. lbs.).
Connect Jumper Lead
Connect to DVOM (-) Lead
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Service Information Number: 07-85-14; Date: 06/09/14 Page 4
Make sure your ammeter is set to read Amperage and not Voltage. (The red lead had to be moved
from the Voltage and Ohm socket to the “A” socket on the meter used in the photos.)
• While keeping the ammeter probe in contact with the negative (-) battery cable terminal and
the end of the jumper wire, remove the battery cable terminal end from the battery post.
• After the current reading stabilizes, read the value displayed on the ammeter. (On push-start
models, if the current reading on the ammeter continues to fluctuate, the smart key may be
too close to the vehicle which will prevent the vehicle from going to sleep.)
• The Dark Current reading shown here is .032 A or 32 mA.
The maximum allowable average dark current draw is 70mA.* If the measured dark current draw
exceeds 70mA, begin diagnostics by removing fuses to isolate circuits one at a time while closely
monitoring the ammeter reading for a corresponding decrease. Once a circuit (or circuits) has been
identified, continue with normal electrical diagnostics of that circuit to determine the source of the
current draw.
* While 70mA is the maximum allowable average dark current draw, this does not mean a vehicle
exhibiting an unusual current draw will always exceed 70mA. In some cases, a vehicle with less
than a 70mA draw may be experiencing an unusual current draw. It is recommended whenever
possible, a like comparison vehicle be used to benchmark the vehicle which has a reported unusual
current draw.
• When repairs are complete, always be sure to reset the customer’s radio station presets and
(if equipped) navigation system favorites before releasing the vehicle.

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