NHTSA ID Number: 11033840
Manufacturer Communication Number: 26-AT-005H TSB
TSB/Document Date: 2026-06-16
Summary
This bulletin provides information related to a Transmission Control Unit (TCU) software update for some vehicles equipped with an 8-speed wet dual clutch transmission (8WDCT). The software update revises the touch point learning variation, improving drivability and judder symptoms. Some 8WDCTs (indicated by a new part number) received an updated clutch spring. The correct TCU software update must be matched with the correct corresponding 8WDCT hardware, otherwise, drivability concerns may occur. This service procedure should be performed prior to any 8WDCT replacements done for drivability/judder concerns.
SUBJECT:
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
ROM ID Information
(AFTER Improvement 8WDCT) – Manual Mode ONLY:
Model
Event
Santa Fe
(TMA)
920
Sonata
(DN8, DN8A)
N-Line Trim
921
Santa Cruz
(NXT)
922
System
AT
TCU
Part Number
ROM ID
Current
Latest
954A0-2N251
(SBW)
VTMPT25XXX720NS9
VTMPT25XXXW720NS0
VTMPT25XXX730NSA
VTMPT25XXXW900NS1
954A0-2N061
(SBW)
VDN8T25XXX900NSB
VDN8T25XXW900NS0
VDN8T25XXX900NSC
VDN8T25XXW900NS1
954A0-2N461
(SBC)
WNX4T25X4X900NS8
WNX4T25X4W900NS0
WNX4T25X4X900NS9
WNX4T25X4W900NS1
NOTE: SBC = Shift By Cable, SBW = Shift By Wire
NOTICE
You must initially perform TCU Updates #920-922 in Manual Mode.
Updates meant for after-improvement 8WDCT (Event # 920, 921, & 922) will ONLY work in
manual mode.
TSB #: 26-AT-005H
Page 6 of 14
SUBJECT:
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
Service Procedure:
DIGITAL DOCUMENTATION
This TSB includes repair validation photos. Refer to the latest Warranty Digital Documentation
Policy for requirements.
NOTICE
Applying the recommended torque to all fasteners is essential to reduce potential issues from
occurring after the service procedure.
Table of Contents
•
Flowchart ..................................................................................................................................8
•
TCU Update Procedure ............................................................................................................9
•
Vehicle Calibration Procedures .............................................................................................. 13
•
Vehicle Driving Inspection ...................................................................................................... 13
TSB #: 26-AT-005H
Page 7 of 14
SUBJECT:
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
Flowchart
Vehicle In
Drivability Concerns
Check 8WDCT
Part Number
BEFORE Improvement
8WDCT
AFTER Improvement
8WDCT
Perform TCU Software
Update (895/896/897)
Perform TCU Software
Update (920/921/922)
Manual Mode ONLY
Vehicle Calibration
• Air Bleeding
• Transmission Learning
• Line Pressure Removal
Mode
• Line Pressure Removal
Mode OFF
• Touchpoint Curve Learning
Driving
Inspection
• Static Test
• Creep Test
• Drive Test
• Other
Fail
Touchpoint Curve Learning
Pass
Vehicle Out
TSB #: 26-AT-005H
Page 8 of 14
SUBJECT:
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
TCU Update Procedure
NOTICE
•
•
•
You must initially perform TCU updates #895, 896, & 897 in Auto Mode.
If the ECU update starts but then fails in Auto Mode, perform the update in Manual Mode
to recover.
You must initially perform TCU Updates #920, 921, & 922 in Manual Mode.
Updates meant for an AFTER improvement 8WDCT (Event # 920, 921, & 922) will ONLY
work in manual mode.
NOTICE
Ensure the vehicle's battery charge is ≥12.3 Volts and the tablet's battery charge is above 30%
before performing a software update, to avoid update failure. Hyundai
recommends connecting a
battery maintainer/charger when performing all ECU updates.
i
Information
•
Turn OFF all lamps (do NOT leave head lamp switch in auto mode) and all accessories.
•
Perform update with the ignition switch in the ON position.
•
Do NOT disconnect any cables connected to the vehicle or scan tool during the update.
•
Do NOT start the engine during the update.
•
Do NOT turn OFF the ignition switch during the update.
1.
Updates #895, 896, & 897:
Perform the TCU update in Auto Mode.
i
Information
Refer to TSB # 25-GI-011H, “ECU
Update Procedure for Tablet-Based
GDS-Smart”, for additional information.
Updates #920, 921, & 922:
Perform the TCU update in Manual Mode.
i
Information
Refer to TSB # 25-GI-011H, “ECU
Update Procedure for Tablet-Based
GDS-Smart”, for additional information.
TSB #: 26-AT-005H
Page 9 of 14
SUBJECT:
2.
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
Verify the ROM ID by selecting the
AT / Transmission system to scan the
vehicle’s current ROM ID.
NOTICE
•
Check the current ROM ID version
and compare it to the ROM ID
Information table before attempting
to perform the software update.
If the update fails, remove the power
connector from the in-cabin fuse box
for at least 5 seconds. Alternatively,
disconnect the negative (–) 12V
battery terminal and wait at least 5
seconds. Reassemble and retry the
update.
•
3.
After the ECU update process shows 100%
complete, follow the prompts on the screen to
cycle the ignition OFF for at least 10 seconds
to reset the control unit (certain models may
take up to 30 seconds).
i
Information
Use the Refresh button to reset the
timer.
TSB #: 26-AT-005H
Page 10 of 14
SUBJECT:
4.
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
DIGITAL
DOCUMENTATION
Using the tablet or GDS screen capture
function, take a screenshot of the ECU
Update "Success" result screen.
Upload the photo to STUI.
NOTE: The VIN/Date/Time/Mileage photo
imprint is NOT required for GDS
screenshots.
6.
Perform an All Systems Fault Code search
and erase DTC history that had incidentally
occurred from the ECU update.
7.
Remove the power connector from the
in-cabin fuse box for at least 5 seconds, then
reconnect it.
i
Information
Alternatively, disconnect the negative (–)
12V battery terminal, wait at least 5
seconds, then reconnect it.
TSB #: 26-AT-005H
Page 11 of 14
SUBJECT:
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
8.
Start the engine to confirm proper operation of
the vehicle.
9.
Proceed to the Vehicle Calibration
Procedures.
NOTICE
If update 895, 896, or 897 fails in Auto Mode, perform the update in Manual Mode using the
password(s) below.
Manual Mode Password:
Event
Menu
Password
895
TM PE THETA 2.5T SOL. VALVE OPERATING FREQUENCY
LOGIC IMPROVEMENT(TCU)
2250
896
DN8 N THETA 2.5T SOL. VALVE OPERATING FREQUENCY
LOGIC IMPROVEMENT(TCU)
2060
897
NX4AT THETA 2.5T SOL. VALVE OPERATING FREQUENCY
LOGIC IMPROVEMENT(TCU)
2460
NOTICE
The following updates MUST be performed in Manual Mode using the password(s) below
(NO Auto Mode available).
Manual Mode Password:
Event
Menu
Password
920
TM PE THETA 2.5T SOL. VALVE OPERATING FREQUENCY
LOGIC IMPROVEMENT(TCU)
0291
921
DN8 N THETA 2.5T SOL. VALVE OPERATING FREQUENCY
LOGIC IMPROVEMENT(TCU)
1291
922
NX4AT THETA 2.5T SOL. VALVE OPERATING FREQUENCY
LOGIC IMPROVEMENT(TCU)
2291
TSB #: 26-AT-005H
Page 12 of 14
SUBJECT:
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
Vehicle Calibration Procedures
1.
Using GDS, perform the following procedures
in this order:
• Air bleeding
• Transmission learning
• Line pressure removal mode
• Line pressure removal mode off
• Touchpoint curve learning
Refer to the shop manual:
• Dual Clutch Transmission System
(Dual Clutch Transmission) > Dual
Clutch Transmission System >
Repair procedures > Installation
Vehicle Driving Inspection
1.
Perform a Static test:
a) Vehicle ignition ON.
b) With brake pedal depressed, shift the
gears as follows:
N > D/N > R/P > D/P > R
c) Confirm vehicle does NOT exhibit
abnormal shock.
d) Repeat steps b and c above 3 times.
2.
Perform a Creep test:
a) Vehicle ignition ON.
b) With brake pedal depressed, shift gear
from P to D.
c) With brake pedal depressed, shift gear
from P to R.
d) Confirm that vehicle starts moving
within 1-2 seconds, without engine
hesitation or juddering.
e) Repeat steps b, c, and d above
3 times.
3.
Check for DTCs and any concerns during the
tests in steps 1 and 2, such as brake signal,
gear tightening, hydraulic pressure, etc.
TSB #: 26-AT-005H
Page 13 of 14
SUBJECT:
DRIVABILITY & JUDDER IMPROVEMENT - 8WDCT TCU UPDATE
FOR VEHICLES WITH 2.5T ENGINES
4.
If the vehicle exhibits delayed acceleration,
jerking, or shift shock after the inspections
above, then re-perform the Touchpoint
curve learning procedure.
5.
If issues are found, follow the normal
diagnostic process.
If issues remain after a detailed diagnostic
process, then replace the 8WDCT assembly
referring to TSB 22-AT-011H, 8-Speed Wet
DCT Replacement Instructions.
i
Information
The transmission assembly should ONLY
be replaced after the TCU update and all
other diagnostic procedures have been
completed. Refer to standard HMA
warranty policy and procedures for DCT
replacement.
TSB #: 26-AT-005H
Page 14 of 14
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TSB/Document ID: 26-AT-005H TSB
Replacement Service Bulletin Number:
MFR Communication Date: 2026-06-05
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: POWER TRAIN
MFR Component System:
MFR Component Subsystem:
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