NHTSA ID Number: 10205881
Manufacturer Communication Number: SB26-054
TSB/Document Date: 2022-01-04
Summary
DT12 Transmission Control Harness Chafing the Transmission Control Module. Classic and New Cascadia vehicles equipped with DT12 transmissions
, built from approximately January 2017 to mid-March 2021, may experience rubbing/chafing on the chassis harness near the transmission.
DT12 Transmission Control Harness Chafing the
Transmission Control Module
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional
Century Class Conventional
Argosy
Cargo
Columbia
122SD and Coronado
26-054
Freightliner
Service Bulletin
Business Class M2
> Cascadia
108SD/114SD
> New Cascadia
General Information
Classic and New Cascadia vehicles equipped with DT12 transmissions, built from approximately January 2017
to mid-March 2021, may experience rubbing/chafing on the chassis harness near the transmission. The damage
caused by this can result in intermittent symptoms and multiple powertrain controller area network (PT-CAN)
fault codes including, but not limited to:
• TCM 521002
• TCM 521221
• TCM 521221
• TCM 521224
The routing and clipping design has changed to prevent this issue. This new design can be applied to vehicles
in the field to prevent future problems.
Follow the procedure below to install the improved transmission control harness routing, as shown in Fig. 1.
10/14/2021
f547666
Fig. 1, Improved Transmission Control Harness
Routing
Procedure
1. Park the vehicle on a level surface, turn the steer tires all the way to the right, shut down the engine, and
set the parking brake. Chock the tires.
2. Open the hood.
3. Disconnect the negative battery cable.
4. Remove the six clipping points that attach the transmission leg of the chassis harness, from the Y near the
bell housing to the TCM connector, as shown in Fig. 2. If harness repair is needed, refer to SB 54-290 for
detailed instructions.
Freightliner Service Bulletin, 12/08/2021
Page 1
DT12 Transmission Control Harness Chafing the
Transmission Control Module
26-054
Freightliner
Service Bulletin
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional
Century Class Conventional
Argosy
Cargo
Columbia
122SD and Coronado
11/19/2021
Business Class M2
> Cascadia
108SD/114SD
> New Cascadia
f547658
Fig. 2, Tie Straps in Original DT12 Transmission
Harness Routing
5. Install the twist-tube heavy duty wrap from start point A to end point B, as shown in Fig. 3, and secure it
with electrical tape to the transmission control harness. Clip and route the transmission control harness
using the dual strap ties at each location, shown in Fig. 3.
2
4
A
5
3
2
1
B
5
11/12/2021
A Start Point
1. Twist-Tube Harness
Wrap
2. Cable Tie Clamps
f547660
B
3.
4.
5.
End Point
Edge Clip Ties
Cable Mount-Tie
Dual Strap Ties
Fig. 3, Installing Twist-Tube Heavy Duty Wrap and Tie
Straps
5.1
Page 2
Route the harness along the path, and install the harness connector on the transmission control unit
(TCU).
Freightliner Service Bulletin, 12/08/2021
DT12 Transmission Control Harness Chafing the
Transmission Control Module
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional
5.2
Century Class Conventional
Argosy
Cargo
Columbia
122SD and Coronado
26-054
Freightliner
Service Bulletin
Business Class M2
> Cascadia
108SD/114SD
> New Cascadia
Secure the harness clipping point next to the TCU connector using a cable tie clamp, as shown in
Fig. 4.
A
1
12/05/2021
f547661
A End Point of Twist-Tube Harness Wrap
1. Cable Tie Clamp
Fig. 4, Securing the Harness Clipping Point at the TCU
Connector
5.3
Secure the harness to the shift controller under the TCU, using the edge clip ties, as shown in Fig.
5.
1
12/05/2021
f547662
1. Edge Clip Ties
Fig. 5, Attaching the Harness to the Shift Controller
with Edge Clip Ties
5.4
Using an edge clip tie and clamp, secure the harness on the lower tab at the rear of the TCU. See
Fig. 6.
Freightliner Service Bulletin, 12/08/2021
Page 3
DT12 Transmission Control Harness Chafing the
Transmission Control Module
26-054
Freightliner
Service Bulletin
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional
Century Class Conventional
Argosy
Cargo
Columbia
122SD and Coronado
Business Class M2
> Cascadia
108SD/114SD
> New Cascadia
1
12/05/2021
f547663
1. Edge Clip Tie
Fig. 6, Attaching the Harness at the Rear of the TCU
with an Edge Clip Tie
5.5
Install all the ties at the top of the shift controller, as shown in Fig. 7.
2
1
3
12/05/2021
f547664
1. Cable Tie Clamps
2. Cable Mount Tie
3. Dual Strap Tie
Fig. 7, Installing Cable
Install a dual tie (item 3) to separate the transmission and chassis harness, and prevent the chassis harness
from touching the shift controller.
Install a single tie (item 2) to secure the chassis harness to the outside of the transmission harness clipping
point.
Install two cable tie clamps (item 1) at the top of the shift controller to secure the transmission harness.
5.6
Page 4
If the original installation had clipping points between the shift controller and the harness junction,
install those once again.
Freightliner Service Bulletin, 12/08/2021
DT12 Transmission Control Harness Chafing the
Transmission Control Module
FLA COE
FLB COE
FLD Conventional
Business Class
FLC 112 Conventional
Century Class Conventional
Argosy
Cargo
Columbia
122SD and Coronado
26-054
Freightliner
Service Bulletin
Business Class M2
> Cascadia
108SD/114SD
> New Cascadia
6. If removed for access, install the battery cable support brackets.
7. For C- or D-box transmissions with battery cables that route over the power take off (PTO) port and have a
cable in the top outboard routing track, install the second dual strap tie on the added harness wrap zone,
between the TCU connector support tie and the forward C-clip tie. See Fig. 8.
1
12/05/2021
f547665
1. Dual Strap Tie
Fig. 8, Installing a Second (Optional) Dual Strap Tie
8. Install the splash shield bracket and secure the air and electrical harness.
9. Install the splash shield. For specific installation steps, see Group 88 of the vehicle workshop manual.
10. Connect the negative battery cable.
Parts
Part Number
BEN 2421002503SCM
23-09796-629
23-13477-100
23-12886-001
23-13322-008
Twist-Tube and Harness Ties
Part Description
TUBE-TWIST, BLK, DIA 25 3 FEET (optional)
CLAMP-CABLE TIE, 1
CLIP-EDGE, 1-3MM, C
MOUNT-TIE, CABLE, D
STRAP-TIE, DUAL, ST
Quantity
1
5
3
1
2
Table 1, Twist-Tube and Harness Ties
Warranty
This is an informational bulletin only. Warranty does not apply.
Freightliner Service Bulletin, 12/08/2021
Page 5
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TSB/Document ID: SB26-054
Replacement Service Bulletin Number:
MFR Communication Date: 2021-12-07
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: POWER TRAIN
MFR Component System:
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