Service

Technical Information

215/20 ENU

2794

2

Complaint - Driving Readiness Cannot be Established or 12-Volt Battery is Discharged
(215/20)
Model Line:

Taycan (Y1A)

Model Year:

As of 2020 up to 2021

Concerns:

High-voltage battery control unit (BMC)

Information:

An error in the High-voltage battery control unit bootloader can result in a discharged 12V
battery or loss of driving readiness in the vehicle.
A discharged 12V battery or loss of driving readiness can be attributed to this BMC bootloader
error by checking the Vehicle Analysis Log (VAL) for four specific fault codes in the Gateway
control unit:
•
•
•
•

U112100 (FF0047) - Data bus – missing message
U112100 (FF004A) - Data bus – missing message
U011200 (FF0004) - High-voltage battery control unit – no communication
U011200 (FF0071) - High-voltage battery control unit – no communication

If the exact four fault codes above are not found in the Gateway, then the bootloader software error
described here is not the cause of the 12V discharge or loss of driving readiness and additional diagnosis
of the vehicle will be necessary.
This bootloader error should be considered independently from the larger-scale 12V battery discharge
concern described in TI 209/20 "Complaint - Discharged 12-Volt Battery after Charging the High-Voltage
Battery (209/20)".
The software solution mentioned in TI 209/20 remains in development and is still expected to be
available in the first quarter of 2021. Review that TI in detail for additional information concerning a
discharged 12V battery.
Action
Required:

Re-program the high-voltage battery control unit with the PIWIS tester software version 39.900.015 (or
higher).
This re-programming updates the BMC software in both model year 2020 and 2021 vehicles.
The BMC software version number in 2020 vehicles may not change with this reprogramming, because
only the bootloader is re-programmed before the old application software (version E870) is then
re-installed. Therefore, the programming action must still be carried out on 2020 vehicles even if the
BMC software version E870 is found in advance.
The BMC software in 2021 vehicles is programmed to version 1441 with this programming action.

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215/
20

Technical Information

Required tools
Information
The vehicle is equipped with a lithium starter battery as standard.
Lithium starter batteries must only be charged using a suitable battery charger that has a current
and voltage-controlled charge map.
For further information about the battery chargers to be used, see  Workshop Manual '270689
Charging battery/vehicle electrical system'.
Tools:

•
•
•

Battery charger with a current rating of at least 90 A and a current and voltage-controlled
charge map for lithium starter batteries, e.g. VAS 5908 Battery charger 90 A
9900 - PIWIS Tester 3 with test software version 39.900.015 installed
VCI connected to the PIWIS Tester 3 via USB cable

Preparatory work
NOTICE
Fault entry in the fault memory and control unit programming aborted due to undervoltage.
•

Increased current draw during diagnosis or control unit programming can cause a drop in voltage, which
can result in one or more fault entries and the abnormal termination of the programming process.



Before starting control unit programming, connect a suitable battery charger with a current rating of at
least 90 A to the vehicle.
NOTICE

Control unit programming will be aborted if the WLAN connection is unstable.
•

An unstable WiFi connection can interrupt communication between the PIWIS Tester and the vehicle
communication module (VCI). As a result, control unit programming may be aborted.



During control unit programming, always connect the PIWIS Tester to the vehicle communication module
(VCI) via the USB cable.
NOTICE

Control unit programming will be aborted if the driver's key is not recognized
•

If the driver's key is not recognized in the vehicle, programming cannot be started or will be interrupted.



Place the driver's key with the back facing down in the area in front of the storage compartment under
the armrest (emergency start tray) in order to guarantee a permanent radio link between the vehicle and
driver's key.

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Technical Information

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NOTICE
Programming interrupted
•

Malfunctions in control unit

•

Risk of damage to control unit



Route the line between the vehicle communication module (VCI) and diagnostic socket on the vehicle
without tension and make sure that the connector is inserted fully into the diagnostic socket.



Check that the rechargeable battery for the PIWIS Tester is charged sufficiently. Connect the PIWIS Tester
to the power supply unit if necessary.

Information
The procedure described here is based on the PIWIS Tester 3 software version 39.900.015.
The PIWIS Tester instructions take precedence and in the event of a discrepancy, these are the
instructions that must be followed.
A discrepancy may arise with later software versions for example.
Work Procedure: 1

Connect a suitable battery charger, e.g. Battery charger 90A, to the jump-start terminals in the
luggage compartment and switch it on.

2

Position the driver's key with the back facing
forward, upright, between the holding struts in the
rear cupholder (emergency start tray) to guarantee
a permanent radio link between the vehicle and
remote control  Emergency start tray.

3

Connect 9900 - PIWIS Tester 3 to the vehicle
communication module (VCI) via the USB cable.
Then connect the communication module to the
vehicle and switch on the PIWIS Tester.

4

Establish operational readiness (switch on ignition).

5

On the PIWIS Tester start screen, call up the 'Diagnostics' application.

Emergency start tray

The vehicle type is then read out, the diagnostic application is started and the control unit selection
screen is populated.

Re-programming high-voltage battery control unit
WARNING
Electrically moved side windows and rear spoiler

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Technical Information

•

Danger of limbs being trapped or severed

•

Risk of damage to components



Do not reach into the danger area.



Keep third parties away from the danger area.



Do not move components or tools into the danger area.

Work Procedure: 1

Re-program the high-voltage battery control unit.
The basic procedure for control unit programming is described in the Workshop Manual 
Workshop Manual '9X00IN Basic instructions and procedure for control unit programming using the
PIWIS Tester'.
For specific information on control unit programming as part of this programming
process, see the table below:
Required PIWIS Tester software version:

39.900.015 (or higher)

Type of control unit programming:

Control unit programming using the 'Campaign'
function in the Additional menu on the PIWIS
Tester by entering a programming code.

Programming code:

K5N6Y

Programming sequence:

Read and follow the information and instructions
on the PIWIS Tester during the guided
programming sequence.
Do not interrupt programming and coding.
A backup documentation process for the
re-programmed software versions starts as soon as
programming and coding is complete.

Software version programmed during
programming:

Model year L (2020) E870
Model year M (2021) 1441
•

•

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On vehicles with model year L (2020), the
software version does not change because
only the bootloader is re-programmed and then
the old application software (version E870) is
re-installed. The measure must therefore be
carried out even if the software version E870
was already read out in advance using the PIWIS
Tester.
Following control unit programming, the
software version can be read out of the

Service

Technical Information

215/20 ENU

2794

2

high-voltage battery control unit in the 'Extended
identifications' menu using the PIWIS Tester.
Programming time (approx.):

approx. 10 minutes

Procedure in the event of abnormal
termination of control unit programming:

• End and restore operational readiness (switch
ignition off and then on again).
• Read out and erase fault memories  Workshop
Manual '9X00IN Basic instructions and procedure for
control unit programming using the PIWIS Tester'.
• Repeat control unit programming by entering the
programming code again.

Procedure in the event of error messages
appearing during the programming
sequence:

 Workshop Manual '9X00IN Basic instructions and
procedure for control unit programming using the
PIWIS Tester - section on "Fault finding"'.

Concluding work
Work Procedure: 1

Read out and erase the fault memories of all control units.
1.1

Press •F7“ in the control unit selection screen ('Overview' menu) to call up the Additional
menu.

1.2

Select the function “Read all fault memories
and erase if required” and press •F12“
('Next') to confirm your selection  Erasing
fault memories.
The fault memories of the control units are
read out.

1.3

Once you have read out the fault memories,
check the fault memory entries.
Erasing fault memories
Information
If control units are found to have faults that
are not caused by control unit programming, these must first be found and corrected. This
work cannot be invoiced under the workshop campaign number.

1.4

Press •F8“ to delete fault memory entries.

1.5

Press •F12“ ('Yes') in response to the question as to whether you really want to delete all
fault memory entries.
The faults stored in the fault memories of the various control units are deleted.

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Information
If fault memory entries for individual control units cannot be deleted, proceed as follows:

1.6

•

End operational readiness (switch off ignition).

•

Disconnect the PIWIS Tester diagnostic connector from the diagnostic socket.

•

Lock the vehicle using the driver's key and remove the driver's key from the
proximity of the vehicle (approx. 10 metres).

•

Wait approx. 15 minutes before unlocking the vehicle again.

•

Restore operational readiness (switch on ignition).

•

Plug the PIWIS Tester diagnostic connector into the diagnostic socket again and restore
communication with the vehicle.

•

Read out the fault memory again and delete any fault memory entries that are stored.

Once you have erased the fault memories,
select the 'Overview' menu to return to the
control unit selection screen  Control unit
selection.

2

End operational readiness (switch off ignition).

3

Disconnect the PIWIS Tester from the vehicle.
Information
Connect the PIWIS Tester to a network as soon as
Control unit selection
you can and log into the PPN in order to transfer the
backup documentation created during this campaign to the PAG systems.

4

Switch off and disconnect the battery charger.

Invoicing
Invoicing:

For documentation and warranty invoicing, enter the labor operations and PQIS coding specified below in
the warranty claim:

APOS

Labour operation

I No.

27942550

Re-programming the high-voltage battery control
unit
PQIS coding:

Location (FES5)

27940

Control unit for high-voltage battery

Damage type (SA4)

1614

Function not as specified

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Technical Information
References:

215/20 ENU

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2

 Workshop Manual '270689 Charging battery/vehicle electrical system'
 Workshop Manual '9X00IN Basic instructions and procedure for control unit programming using the
PIWIS Tester - section on "Fault finding"'.

 Workshop Manual '9X00IN Basic instructions and procedure for control unit programming using the
PIWIS Tester'

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.

© Porsche Cars North America, Inc.

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