SIL 22-1K2K-23
October 26, 2023
Page 1 of 7
SUBJECT:

Separator Plate/Software Change for Hyundai DTC P0847/P0872 Issue

MODELS AFFECTED:

1000 xFETM, T1000 xFETM and 2500 SeriesTM Transmissions

VEHICLES AFFECTED: Hyundai Mighty Truck, Hyundai County Bus and Hyundai Pavise Truck

Description of Complaint:
In some Hyundai Motor Company (HMC) Mighty Trucks, HMC County Buses and HMC Pavise Trucks operating
with 1000 xFE, T1000 xFE and 2500 Series transmissions, the Check Trans lamp may illuminate along with setting
Diagnostic Trouble Code (DTC) P0847, Transmission Fluid Pressure Switch 2 Circuit Low and/or DTC P0872,
Transmission Fluid Pressure Switch 3 Circuit Low. The transmission may have poor shift quality.

Cause:
The DTCs related to the Pressure Switch Manifold are caused by either Pressure Switch 2 or Pressure Switch 3
applying when they should not be applied. These incorrect Pressure Switch applies occur immediately after lockup
release completes and are the result of a pressure spike caused by rapid exhaust of the lockup clutch.

Continuous Product Improvements:
Separator Plate Change:
The separator plate has been modified by decreasing the Torque Converter Clutch (TCC) Exhaust Backfill
orifice diameter from 6.00 mm to 4.25 mm. Refer to Figure 1 for orifice location and part number identification.
This orifice diameter change reduces flow and pressure spikes in the exhaust backfill fluid circuit and increases
the lockup release time.

DH / SL9141EN

6628007

Copyright © 2023 Allison Transmission, Inc. All Rights Reserved.

SIL 22-1K2K-23
October 26, 2023
Page 2 of 7

New P/N Location

4.25 mm orifice

6628097

Figure 1. Separator Plate TCC Exhaust Backfill Orifice
The separator plate orifice change is being implemented into all new production builds.
Neutral at Stop (NAS) Separator Plate
Former P/N 29568757 >>> Current P/N 29572828
Former NAS separator plate, P/N 29568757, has been completely canceled.
Standard Separator Plate (non-NAS)
Former P/N 29568756 >>> Current P/N 29572827
Former standard separator plate, P/N 29568756, will be available until stock is depleted, at which time the
part will be completely canceled.
NOTE: Hyundai vehicles must use the current NAS separator plate, P/N 29572828, during service repairs
related to this concern. The former NAS separator plate, P/N 29568757, is not forward compatible
in these vehicles.
For all other customer vehicles, the former and current separator plates (NAS and Standard) are
backward and forward compatible.
Changes are being made to the Control Module Assemblies P/N 29558370 (NAS) and P/N 29558484 (Standard,
non-NAS) to include new separator plates P/N 29572828 (NAS) or P/N 29572827 (Standard, non-NAS),
respectively.
Service Procedure:
If DTCs P0847 and/or P0872 are experienced in one of these vehicles, refer to the Service Manual SM5818
to replace the separator plate.
Copyright © 2023 Allison Transmission, Inc. All Rights Reserved.

SIL 22-1K2K-23
October 26, 2023
Page 3 of 7

Software Update:
A software update has been created to reduce the lockup pressure floor from 850 kPa to 550 kPa. The lower
lockup pressure floor leads to lower flow and reduced pressure spikes in the exhaust backfill fluid circuit.
5th Generation Calibrations:
Software level B197 includes the reduced lockup pressure floor required to improve pressure spikes. If a 5th
Generation transmission experiences these concerns, the software level must be updated to software level B197
or later, in addition to the separator plate change mentioned above.
Service Procedure:
Confirm that the current TCM software level is older than B197. The software level can be found by connecting the
TCM with Allison DOC®. The DTC and General Info tab will show the Cal ID in the TCM Information section. The
first four digits of the Cal ID indicate the current software level. The software level must be updated if the second
through fourth digits are less than 197.

Figure 2. Current Software Level Example in Allison DOC

Copyright © 2023 Allison Transmission, Inc. All Rights Reserved.

SIL 22-1K2K-23
October 26, 2023
Page 4 of 7
If the current software level is older than B197, update software to B197 or later by programming based on the
TCM serial number in TCM ReflashTM. After programming is complete, use Allison DOC to verify that the second
through fourth digits of the Cal ID are 197 or greater (refer to Figure 3).

Figure 3. Updated Software Level Example in Allison DOC
6th Generation Calibrations:
6th Generation Controls Production Calibration (PC) BCN 241 Software, which was released on October 12,
2023, includes the reduced lockup pressure floor required to improve pressure spikes. Refer to WATCH #606
for additional details. If a 6th Generation transmission experiences these concerns, the software level must be
updated to software level B241 or later.
Service Procedure:
Confirm that the current TCM software level is older than B241. The software level can be found by connecting the
TCM with Allison DOC. The DTC and General Info tab will show the Cal ID in the TCM Information section. The
first four digits of the Cal ID indicate the current software level. The software level must be updated if the second
through fourth digits are less than 241.

Copyright © 2023 Allison Transmission, Inc. All Rights Reserved.

SIL 22-1K2K-23
October 26, 2023
Page 5 of 7

Figure 4. Current Software Level Example in Allison DOC
If the current software level is older than B241, then update software to B241 or later by programming based on the
TCM serial number in TCM Reflash. To receive the latest software level, it is necessary to check the box labeled
“Download Latest Calibration” on the Add screen in TCM Reflash (refer to Figure 5). After programming is complete,
use Allison DOC to verify that the second through fourth digits of the Cal ID are 241 or greater (refer to Figure 6).

Copyright © 2023 Allison Transmission, Inc. All Rights Reserved.

SIL 22-1K2K-23
October 26, 2023
Page 6 of 7

Figure 5. Updating to Latest Software Level in TCM Reflash
NOTE: The “Download Latest Calibration” option in TCM Reflash should only be used when there is a
specific need to update the software.

Copyright © 2023 Allison Transmission, Inc. All Rights Reserved.

SIL 22-1K2K-23
October 26, 2023
Page 7 of 7

Figure 6. Updated Software Level Example in Allison DOC
NOTE: The software change to lower the lockup pressure floor outlined above only affects 1000 xFE
and T1000 xFE vocational models. This is because the lockup pressure floor is already lower in other
vocational models. Therefore, 2500 series applications such as the Hyundai Pavise Truck do not require a
software change.

Additional Information:
If a vehicle is NOT a part of the three named vehicle applications and experiences DTC P0847 and/or DTC P0872,
refer to Troubleshooting Manual TS8795 to correct the concern.

Copyright © 2023 Allison Transmission, Inc. All Rights Reserved.