Symptom-based workshop manual

Service
67/25

ENU

9470

Symptom Lighting - White message in Instrument Cluster "Auxiliary Brake Light (3rd Brake Light)
Defective" - Comply With Test Instruction (SY 67/25)
Vehicle Type:

Taycan (Y1A)
Taycan 4 (Y1A)

Model Year:

As of 2021

Equipment:

Sports saloon (M-No. K8S)

Concerns:

Auxiliary brake light

Symptom:

The customer complains about a white message in the "Auxiliary brake light" instrument cluster.
In the fault memory of the control unit for the rear-end electronics (BCM2), one of the following fault
memory entries is stored:
•
•

9

B12C615 - Rear lid auxiliary brake light, short circuit to positive or open circuit (09F904)
B12C611 - Rear lid auxiliary brake light, short circuit to ground (09F902)

Cause:

The fault can occur due to various fault sources in the auxiliary brake light circuit.
Replacing the auxiliary brake light is not necessarily effective.

Action:

If there is a customer complaint, check the control of the auxiliary brake light and the auxiliary brake light.

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Installation
location:

Installation location of auxiliary brake light

Required parts and materials as needed
Information
For checking the auxiliary brake light, no parts are required.
Parts Info:

Part no.

Designation
– Location of use

Quantity

Required parts for vehicles where the auxiliary brake light has a defect.
9J1945211E*

⇒ Raised brake light
– Rear window

1 unit

⇒ Raised brake light
– Rear window

1 unit

or
9J1945087E*

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Required parts for vehicles where the rear window has a defect.
9J1845051xx*

⇒ Rear window

1 unit

PAD004660

⇒ 2-component window adhesive set
– Rear window

1 unit

*Determine the variant required for the respective vehicle using the vehicle identification number in the
Porsche Spare Parts Catalogue (PET2).
Material:

Required material for vehicles where the rear window has a defect (usually already available in the Porsche
Center):
Part no.

Designation
– Location of use

Quantity

D00940104

⇒ Cleaning solution
– Rear window

Quantity as required
(max. 1 unit)

PAD181220

⇒ Primer
– Rear window

Quantity as required
(max. 1 unit)

D181802M1

⇒ Activator
– Rear window

Quantity as required
(max. 1 piece)

9A700950000

⇒ Applicator
– Rear window

Quantity as required
(max. 1 unit)

00004330332

⇒ Cutting wire for loosening glass panes
– Rear window

Quantity as required
(max. 1 piece)

Required tools
Tools:

•
•
•

Standard measuring connection cable for external power supply of lights, e.g. 9684/3 - MLK measuring
cable 1.2
External 12-volt power supply for external power supply, e.g. commercially available 12-volt battery
Commercial available multimeter, e.g.V.A.G 1526E - hand multimeter

Additional tool required for vehicles where the rear window has a defect:
•

scraper, e.g. commercially available scraper (U-shape)

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Testing auxiliary brake light and analysing fault source
1

If operational readiness was previously established (ignition switched on): End operational readiness
(switch off ignition).

2

Pull out fuse for auxiliary brake light and check for damage.
Test criteria:
•
•
•

Defective/burnt out
Correctly plugged in
Contact of the fuse OK

Information
The potentially affected fuse of the auxiliary brake light is located behind the luggage compartment
trim, storage compartment cover, on the right (to the side). The fuse assignment can vary due to the
equipment.
The corresponding fuse assignment must be determined with the affected VIN in the PCSS.
Assessment
( )

Fuse is not damaged.

Action
Fuse OK.
Þ 3.
Continue with Step ⇒

✗)
(✗

3

4

Fuse is damaged.

Fuse not OK.
Repair damage or replace fuse and check function
of auxiliary brake light again.
Þ 11 and ⇒
Þ 12,
Function restored: Perform Steps⇒
end of action.
Þ 3.
Function not restored: Continue with Step ⇒

Þ Checking auxiliary brake
Remove auxiliary brake light⇒
light connection -1-, check electric plug connection
Þ Checking auxiliary brake light connection -2- and
⇒
Þ Checking auxiliary brake light
soldering points⇒
connection -3- for damage and correct locking.
⇒ Workshop Manual '947019A8 Removing and
installing auxiliary brake light'
Test electric lines (cable lines) from soldering points

Þ Checking auxiliary brake light connection -3- to
⇒

Þ
electric plug connection for auxiliary brake light for ⇒
Checking auxiliary brake light externally -2- continuity
or resistance.

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Checking auxiliary brake light connection

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9

Information
If one or more of these lines (cable lines) have an optical or metrological defect, they can be repaired by
replacing the cable.
Replacing additional components is not expedient until the following test instruction is completed.
Assessment

Action

( )

Electric plug connection and electric lines
of the auxiliary brake light are OK.

Þ 5.
Continue with Step ⇒

✗)
(✗

Electric plug connection and / or electric
lines (cable lines) of the auxiliary brake
light not OK.

Repair electric plug connection and / or electric lines
or lock correctly, reconnect auxiliary brake light and
check.
Þ 10 to ⇒
Þ 12,
Function restored: Perform Steps⇒
end of action.
Þ 5.
Function not restored: Continue with Step ⇒

5

Þ
Check the function of the auxiliary brake light ⇒
Checking auxiliary brake light externally -1- using an
external power supply, for example using a 12 volt
Þ Checking auxiliary brake light externally -2-.
battery⇒

Checking auxiliary brake light externally
Assessment
( )

Auxiliary brake light lights up.

Action
Auxiliary brake light OK.
Þ 6.
Continue with Step ⇒

✗)
(✗

Auxiliary brake light is not on.

Auxiliary brake light defective.
Replace auxiliary brake light.
For procedure, see:
⇒ Workshop Manual '947019A8 Removing and
installing auxiliary brake light'
Þ 11 and ⇒
Þ 12, end
After repair, carry out Steps⇒
of the action.

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6
7

67/25

Symptom-based workshop manual

Remove C-pillar trim (upper part) on the left and right.

⇒ Workshop Manual '706819A1 Removing and installing C-pillar trim (upper part)'
Þ Checking electric lines and plug connections for auxiliary
Check electric lines for auxiliary brake light ⇒
Þ Checking electric lines and plug
brake light -1- and electric plug connections for auxiliary brake light ⇒
Þ Checking electric lines and plug connections
connections for auxiliary brake light -2- on rear window ⇒
for auxiliary brake light -3- for damage and/or correct locking.

Checking electric lines and plug connections for auxiliary brake light
8

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Þ Checking electric lines
Check electric lines (cable lines) from electric lines for auxiliary brake light ⇒
Þ
and plug connections for auxiliary brake light -1- to electric plug connections for auxiliary brake light ⇒
Checking electric lines and plug connections for auxiliary brake light -2- for continuity and/or resistance.

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Information
If one or more of these lines (cable lines) have an optical or metrological defect, they can be repaired by
replacing the cable.
Replacing additional components is not expedient until the following test instruction is completed.
Assessment
( )

Action

Electric lines and plug connections for
auxiliary brake light on the rear window are
not damaged.

Electric lines on rear window OK.
There is a problem with the supply lines outside the
rear window.
Continue troubleshooting there, after repair,
Þ 9 to ⇒
Þ 12, end of action.
perform Steps ⇒

✗)
(✗

Electric lines for auxiliary brake light on the
rear window are damaged.

Electric lines on rear window not OK.
Replacing rear window.
For procedure, see:
⇒ Workshop Manual '648619A7 Removing and
installing rear window'
Þ 11 and ⇒
Þ 12, end of
After repair, perform Steps ⇒
the action.

✗)
(✗

9

Electric plug connection and / or electrical
lines (cable lines) for auxiliary brake light
on rear window not OK.

Repair or lock electric plug connection correctly,
reconnect auxiliary brake light and test.
Þ 9.
Function restored: Continue with Step ⇒
Function not restored: Continue troubleshooting
Þ 9 to ⇒
Þ 12 after
in another way, perform Steps ⇒
repair, end of action.

Install C-pillar trim (upper part) on the left and right.

⇒ Workshop Manual '706819A1 Removing and installing C-pillar trim (upper part)'

10 Install auxiliary brake light.
⇒ Workshop Manual '947019A8 Removing and installing auxiliary brake light'
11 Read out all fault memories, process and delete existing faults if necessary.
12 Exit the diagnostic application. Switch off ignition. Disconnect P90999 - PIWIS Tester 4 from the
vehicle.

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Labor position and PCSS encryption
Labor position:
APOS

Labor operation

I No.

94700140

Check auxiliary brake light (fuse not OK)

94700141

Check auxiliary brake light (electric lines / electric
plug connection of auxiliary brake light or auxiliary
brake light not OK)

94700142

Check auxiliary brake light (electric lines / electric
plug connection of auxiliary brake light or auxiliary
brake light not OK)

94700143

Check auxiliary brake light (electric lines on rear
window not OK)
PCSS encryption:

Location (FES5)

94700

Auxiliary brake light

Damage type (SA4)

1611

not functioning

Important Notice: Technical Bulletins issued by Porsche Cars North America, Inc. are intended only for use by professional automotive technicians who have attended Porsche service training courses. They are
written to inform those technicians of conditions that may occur on some Porsche vehicles, or to provide information that could assist in the proper servicing of a vehicle. Porsche special tools may be necessary in
order to perform certain operations identified in these bulletins. Use of tools and procedures other than those Porsche recommends in these bulletins may be detrimental to the safe operation of your vehicle, and
may endanger the people working on it. Properly trained Porsche technicians have the equipment, tools, safety instructions, and know-how to do the job properly and safely. Part numbers listed in these bulletins
are for reference only. The work procedures updated electronically in the Porsche PIWIS diagnostic and testing device take precedence and, in the event of a discrepancy, the work procedures in the PIWIS Tester
are the ones that must be followed.

© 2025 Porsche Cars North America, Inc.

Sep 3, 2025
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