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Bulletin #: 2518.4

Advanced Technical Information

Part ID: 2708

Y1A, Y1B, Y1C- High-Voltage (HV) Battery Measurements during HV Battery Repair
Vehicles Affected
Models

Model Year

Model Type

VIN Range

Vehicle-Specific Equipment

Taycan

All

Y1A, Y1B, Y1C

All

N/A

Revision History
Revision

Release Date

0

November 6, 2025

1

November 11, 2025

2

December 1, 2025

3

March 6, 2026

Changes
•
•
•

•
•
4

April 1, 2026

Original document

• Update to Figure 2
Update to IR Testing Pass/Fail Criteria section on page 8

• Update to General DST Procedure Updates section
Update to IR Testing Pass/Fail Criteria section failure threshold
• Update to Model Years

• Addition of Figure 2, 4, and 5
• Update to Service Information
• Update to General DST Procedure section
Update to DST Procedure for 28-module Taycan Battery Pack section
Update to DST Procedure for 33-module Taycan Battery Pack section
• Update to IR Measurement Procedure section
•

•

Update to Figure 2, and 4
Update to Warranty

Condition
All Taycan HV batteries are subject to dielectric strength testing after repair according to Workshop Manual WM
270803A5 Performing measurements on the high-voltage battery. In some cases, the VAS 6972 measurement
equipment can report a failed Dielectric Strength test (DST). This bulletin serves two purposes. One is to provide an
updated test procedure to more accurately isolate test failures, and the second is to serve as an updated diagnostic
guide for interpreting the test results. Every safety warning and HV certification requirement from the Workshop
Manual also applies to the work instructions contained in this document. Measurement specifications or component
replacement requirement guidance listed in this bulletin take precedence over those stated in the Workshop Manual
until this bulletin is removed or the workshop manual is updated.

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Bulletin #: 2518.4

Advanced Technical Information

Part ID: 2708

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Technical Background
When performing post-repair validation of a Taycan HV battery, it is important to differentiate the purposes of
dielectric strength testing and insulation resistance (IR) measurements. Dielectric strength tests assess the
ability of the battery’s insulation system to withstand a specified high voltage limit without breaking down, ensuring
the overall integrity and safety of the high-voltage system under extreme electrical stress. In contrast, IR
measurements quantify the resistance of the insulation material to direct current leakage, indicating the quality and
degradation of the insulation over time before leading to an insulation fault. Both tests are required according to the
Workshop Manual.

Service Information
The updated work instructions for dielectric strength testing are differentiated by HV battery variant in the
sections below. Updated IR measurement work instructions apply to both variants. The general order of
measurements taken at each point is the same as described in WM 270803A5 Performing measurements on the
high-voltage battery.
1. Split the battery modules into sections by removing the specified busbars.
2. Perform an IR measurement on the first section.
3. Perform a DST on that section.
4. Perform an additional IR measurement on that section.
5. Move on to the next section.
Flowcharts of this process for each battery variant are available in figures to follow. The end step “Proceed with
subsequent work” can refer to the next measurement point or completion of the repair depending on scenario.
General DST Procedure Updates:
• Due to the limited cable length of the VAS 6972, grounding to the equipotential bonding line is not possible
from all measurement points. The use of the original VAS 6972 ground clamp on the equipotential bonding
line is therefore no longer permitted.
▷ Hand-start a clean lid screw into the frame near the designated measurement point and clamp the
VAS 6972 securely to it to ground the tool.
▷ An equipotential bonding test can be performed between the screw and equipotential bonding line to
verify a good ground path.
• Suggested grounding points for DST and IR testing on both 28- and 33-module Taycan battery packs have
been modified from WM 270803A5 and are detailed below in figures 1 and 3.
• During a DST, only personnel with a 40 Cal Arc Flash suit and Porsche-approved PPE may be permitted
within the cordoned HV safety zone around the battery pack.
• Perform the self test and safety test for the VAS 6972 tool every time before first use during each repair.

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Bulletin #: 2518.4

Advanced Technical Information
•

Part ID: 2708

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Do not perform an additional DST back to back on any measurement point to confirm a value.
▷ Any DST must only be performed once per point if a result is obtained. Only retry a test if it does not
yield a result.
▷ If a valid result (pass/fail) is still not possible after 2 attempts at the same point, contact technical
support via PRMS.
▷ Do not perform a follow up DST after replacing modules in a failed section.

DST Procedure for 28-module Taycan Battery Pack (Figure 1)
• Only two DSTs are to be performed on a 28-module battery pack during repair.
• The busbar indicated in red must be removed prior to measurements at either point.
• Perform an IR test at points 1 and 2 before the DST at those points.
• Perform a DST only at points 1 and 2 shown below for each repair scope.
• The yellow boxes in Figure 1 designate the sections of frame where a lid screw can be hand-started to
ground the dielectric strength tester.
• Also perform IR tests at points 1 and 2 after a DST, with the negative probe in contact with a clean spot on
the silver frame surface designated by the yellow boxes.
• If the final IR test at measurement point 1 fails, remove busbars and CMC connections from each module
shaded in dark blue for further IR testing as described in the following Updated IR Measurement Procedure
sections.
• If the final IR test at measurement point 2 fails, remove busbars and CMC connections from each module
shaded in light blue module for further IR testing as described in the following Updated IR Measurement
Procedure sections.
• EXAMPLE: Point 1 passes DST and point 2 fails.
▷ Perform IR tests on each light blue module in the failing section (In this example, section 2). No
additional work is required for the passing modules in section 1.

Figure 1 - 28-module HV Battery measurement points

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Bulletin #: 2518.4

Advanced Technical Information

Part ID: 2708

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Figure 2 - 28-module Flowchart

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Advanced Technical Information

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DST Procedure for 33-module Taycan Battery Pack (Figure 3)
• Only a total of three or four DST’s are to be performed on the 33-module battery pack during repair,
depending on scope.
▷ Perform a DST only at points 1, 2, and 3 for any repair scope involving the lower-level modules.
▷ Repair scopes in only the upper “T” section require an initial DST (in addition to the points in figure 2)
at the mid-pack fuse as shown in step 3.9.3 of Safety test after assembly work on the high-voltage
battery with 33 modules in WM 270803A5. Only proceed with removing lower lid if this initial DST
fails.
• If removed, the upper “T” Section should be placed aside on a VAS 6762/44 Insulating mat during testing.
• Perform an IR test at points 1, 2 and 3 before the DST at those points.
• The yellow boxes in Figure 3 designate the section of frame where a lid screw can be hand-started to
ground the dielectric strength tester. If performing a DST on the mid-pack fuse, use the location on the
upper “T” section to ground the negative clamp.
• Perform IR tests at points 1, 2, and 3 after a DST, with the negative probe in contact with a clean spot on
the silver frame surface designated by the yellow boxes.
• If the final IR test at measurement point 1 fails, remove busbars and CMC connections from each module
shaded in dark blue for further IR testing as described in the following Updated IR Measurement Procedure
sections.
• If the final IR test at measurement point 2 fails, remove busbars and CMC connections from each module
shaded in light blue for further IR testing as described in the following Updated IR Measurement Procedure
sections.
• If the final IR test at measurement point 3 fails, remove busbars and CMC connections from each module in
the upper “T” section for further IR testing as described in the following Updated IR Measurement Procedure
sections.
• EXAMPLE: It is possible for battery to have point 1 pass, point 2 pass, and point 3 fail the DST. It would then
only be required to perform further IR tests on each module in the upper “T” section. No additional work
would be required for the passing lower sections.

Figure 3 - 33-module HV Battery measurement points

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Bulletin #: 2518.4

Advanced Technical Information

Part ID: 2708

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Figure 4 - 33-module Lower Section Flowchart

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Advanced Technical Information

Part ID: 2708

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Figure 5 - 33-module Upper Section Flowchart

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Bulletin #: 2518.4

Advanced Technical Information

Part ID: 2708

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Updated IR Measurement procedure after a DST Failure:
• Perform IR tests at each measurement point in Figures 1 and 3 before and after a DST at that point.
▷ If the DST passes but IR falls below the thresholds in figures 2, 4, and 5, proceed with IR testing each
module.
▷ If the DST fails but all modules in the section pass IR, reconnect the modules and proceed with the
repair.
• For repair scopes only in the upper level, IR test the upper and lower sections separately after an initial DST
failure.
• Discharge capacitance and remove all the busbars from modules of failed section(s) differentiated by light
and dark blue in Figures 1 and 3.
• Monitor the rate of capacitive discharge on each busbar during removal. Noticeably slow discharge or
inconsistent voltage behavior can also point to a damaged module. Keep in mind that a battery with high
SoC will also lengthen the capacitive discharge process.
• Replace all busbars removed during repair.
• Carefully disconnect all CMC connectors from the modules of failed section(s).
• Two options are available for IR testing in the PIWIS measuring equipment menu. Select “HV System.”
• IR tests are to be performed on every module at each positive terminal twice in a row. The measurements
should be taken immediately back-to-back on on each module before advancing to the next one.
• IR testing is conducted using VAS 6558A or VAS 6558B with both 1000V straight probes on the test leads.
• The equipotential bonding cable is no longer used as a ground point for these module IR tests.
• When IR testing a module on the positive terminal: Contact the positive terminal with the red test probe as
shown in Figure 6.

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Bulletin #: 2518.4

Advanced Technical Information

Part ID: 2708

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Module IR Testing Procedure: Positive Terminal (Figure 6)
• Place the red probe at the edge closest to the black plastic surrounding the terminal to avoid scratching the
conductive surface.
▷ CAUTION: pay attention to the angle of the red probe in this case. Avoid contact with the side of the
probe and the edge of the module housing. Use a plastic probe cap to expose only the tip of the probe
if available.
• Maintain contact with the black probe to the module case in the center. Ensure that the module casing
surface is clean at the point of contact.
• The equipotential bonding cable is not suitable as a ground point during this test. Use both straight probes
directly on the module to isolate conductive influences.

Figure 6 - IR Test at Positive Terminal

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Bulletin #: 2518.4

Advanced Technical Information

Part ID: 2708

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IR Testing Pass/Fail Criteria (Figure 7)
• Shown below is an example of passing test result of >5000 MΩ. This is the reading displayed when IR
measures above the 500 MΩ measuring threshold.
• IR values between 200 MΩ and 500 MΩ are also acceptable for the second measurement on a terminal.
• If the first IR test on either module terminal fails, but the second one passes, the module is okay and should
not be replaced.
• If any second terminal IR test shows a number below 200 MΩ, this is considered a failure.
• If IR is below the measurement threshold, the IR test won’t complete in the measurement equipment
display. If the IR test fails to produce a value after multiple attempts on any module terminal, replace it.
• Document any failures in the “Module insulation Resistance Template” Excel file attachment and attach to
the repair PCSS entry.

Figure 7 - Insulation resistance measurement in PIWIS Tester

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Bulletin #: 2518.4

Advanced Technical Information

Part ID: 2708

Warranty

2

For documentation and warranty invoicing, enter the working position and PCSS encryption specified below in the
warranty claim:
APOS

Labor operation

27080375

High-voltage battery measure

I No.

In the event of a DST/IR failure, use the following labor operation for additional labor:
APOS

Labor operation

27080499

Insulation Resistance measurements

I No.

PCSS encryption:
Location (FES5)

2708G

Cell block module

Damage type (SA4)

4053

Voltage loss/drop

Search Items
HV Battery, Isolation resistance, Dielectric strength, Safety test after assembly work

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.

6000018746
© 2026 Porsche Cars North America, Inc.

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