SIL 3­EP­16
January, 2016
Page 1 of 31
SUBJECT:

Replacing the AC Busbar Assembly and AC Terminal Block Inside the Dual Power Inverter Module
2 (DPIM2)

MODELS AFFECTED:

H 40/50 EP SystemTM Equipped With DPIM2

Tools Required
• J­51586 Tab Bending Tool (available at Allison.service­solutions.com)
• J­46708 Multimeter (available at Allison.service­solutions.com) or equivalent
• Electrostatic Discharge Wrist Strap (Tool Number 7744 (available at Allison.service­solutions.com) or
equivalent) (Refer to Figure 6)
• Pick or Small Flat Blade Screwdriver
• Torx PlusTM T25 Bit
• 6mm Hex Key
• 8mm Hex Socket
• 11mm Hex Socket
• Loctite® 242
• Loctite® 425
Parts Required
• P/N 29540714 – Cover Gasket
• Wire Ties (4 inch and 6 inch – Nylon 6/6 or approved equivalent)

Introduction:
This Service Information Letter (SIL) announces the availability of the AC (Alternating Current) busbar, AC terminal
block, and related components and includes the procedure to replace the AC busbar and AC terminal block. The
availability of this part eliminates the need for a complete DPIM replacement under certain failure conditions.
NOTE: Replacement of the AC Busbar and Terminal block is not a warrantable repair by Allison
Transmission, Inc. if damaged has been caused by arcing. Contact Allison TAC at (800) 252­5283 prior to
initiating repairs on a DPIM that is under warranty.

BC / SL7632EN

2777734

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 3­EP­16
January, 2016
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NOTE: Refer to the attachment at the end of this SIL for information regarding the name and location of
components within the DPIM2.

NOTE: Perform the necessary visual inspection prior to ordering parts. The parts are NOT available as a
complete kit. All necessary components must be ordered individually.
Refer to Figure 1 and Figure 2 for locations of the AC busbars, terminal blocks and related components. Refer to
Table 1 for list of Service Parts.

Figure 1. DPIM2 Busbar Locations

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SIL 3­EP­16
January, 2016
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Figure 2. Location of AC Terminal Block, Screws, and BCA Standoff
Refer to Table 1 for Service Parts.
Table 1. Service Parts
Item Number

Part Name

Part Number

1

AC Bus Assembly – A

29546765

2

AC Bus Assembly – B

29546764

3

AC Terminal Block – A and B

29546806

4

Screw – M5x22mm

29540587

5

Screw – M5x18mm

29540732

6

BCA Standoff

29548554

Diagnosis:
The AC busbar assembly and AC terminal block may need to be replaced if the HV lug bolt has become loose and
components are damaged by electrical arcing. Refer to Figure 3 and Figure 4.

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SIL 3­EP­16
January, 2016
Page 4 of 31

Figure 3. Damage to AC Terminal Block Caused by Electrical Arcing

Figure 4. Damage to AC Busbar Caused by Electrical Arcing
WARNING: DO NOT rely on the High Voltage Interlock Loop (HVIL) or control systems to de­energize
the system. Always perform the Electrical Disconnect Verification Procedure to be sure the system is
discharged before servicing components.
DO NOT attempt to bypass any High Voltage Interlock for any reason. Tampering with the HVIL may result
in injury. Failure to follow proper safety procedures may result in serious personal injury or death.

WARNING: Smoke inside the DPIM contains harmful Copper Oxide. Use proper protective equipment to
protect your skin and eyes from contact. Avoid inhalation of smoke.

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SIL 3­EP­16
January, 2016
Page 5 of 31

NOTE: Allison Transmission, Inc. requires the removal of the DPIM from the vehicle prior to AC Busbar and
AC Terminal Block replacement. Prior to removal of the DPIM, refer to the H 40/50 EP SystemTM System
Troubleshooting Manual (TS5812EN) and perform the Electrical Disconnect Verification Procedure.

NOTE: Internal DPIM repairs should NOT be performed if smoke and/or water damage are present.
Photograph the smoke and/or water damage and contact Allison TAC at (800) 252­5283.

NOTE: Complete the DPIM Check List prior to replacing the AC busbar assembly and AC terminal block
to ensure additional components have not been damaged. All cables (AC and DC) must be removed from
the DPIM prior to taking measurements shown on the DPIM Check List. For additional information, refer to
H 40/50 EP SystemTM Troubleshooting Manual (TS5812EN).

Figure 5. DPIM2 (Main Cover and Lug Box Covers Removed)

The procedures contained in this SIL are organized into the following sections:
Section 1: Removal of Main Cover and HVIL Circuit Card
Section 2: Removal of BCA Card Mounting Shelf
Section 3: Removal of the AC Busbar Assembly and AC Terminal Block
Section 4: Installation of the New AC Terminal Block and AC Busbar Assembly
Section 5: Installation of BCA Card Mounting Shelf
Section 6: Installation of HVIL Circuit Card and Main Cover

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 3­EP­16
January, 2016
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Section 1: Removal of Main Cover and HVIL Circuit Card
NOTE: All circuit cards in the DPIM2 are sensitive to electrostatic discharge (ESD). ESD damage can be
caused by voltage levels that cannot be felt by humans. When working on the DPIM2, ALWAYS wear an
ESD wrist strap to ground any possible electrostatic charge. The strap should be worn around the wrist
with the alligator clip securely attached to the DPIM chassis. Refer to Figure 6.

Figure 6. Electrostatic Discharge Wrist Strap (Tool Number 7744 Shown)
1. Using a Torx PlusTM T25 bit, remove twenty­six (26) M5x18mm machine screws that secure the Main
Cover to the DPIM Housing (refer to Figure 7). Set the screws aside for reassembly. Remove the Main
Cover. Discard the cover gasket.

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SIL 3­EP­16
January, 2016
Page 7 of 31

Figure 7. DPIM Main Cover
2. Exercising care, cut one (1) wire tie at location shown in Figure 8. Do NOT remove any wire ties that pass
through the HVIL Circuit Card. Leaving the severed wire ties in place will provide a visual aid for wire tie
locations during installation of the replacement circuit card.

Figure 8. HVIL Circuit Card – Wire Tie Location

3. Cut the two (2) wire ties at locations shown in Figure 9 and remove them from the mounts. The wire
tie mounts do NOT have to be removed from the DPIM Housing unless they interfere with the removal
or installation of the HVIL circuit card.

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 3­EP­16
January, 2016
Page 8 of 31

Figure 9. HVIL Circuit Card – Two (2) Wire Tie Locations

CAUTION: Do NOT pull on the wires when removing connectors, doing so may pull the pins out of the
connector.

4. When removing connectors, push down on the tab at Location 1 and push the harness out of the connector
at Location 2 with a Pick or Small Flat Blade Screwdriver (refer to Figure 10).

Figure 10. HVIL Circuit Card Connector Removal

5. Remove three (3) wire harness connectors from HVIL Circuit Card surface mount connectors by gently
depressing the retaining tab with a pick or small flat blade screwdriver. Refer to Figure 11.
NOTE: Use care to avoid bending or damaging the circuit card connectors.

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SIL 3­EP­16
January, 2016
Page 9 of 31

Figure 11. HVIL Circuit Card – Three (3) Harness Connector Locations
WARNING: Any conductive material (i.e. screws, bolts, nuts, etc.) can cause a short inside the DPIM that
will result in permanent and irreversible DPIM damage. All hardware must be accounted for throughout
the service procedure.

6. Using an 8mm hex socket, remove the four (4) M5 nut/washer assemblies as shown in Figure 12. Disconnect
the two (2) wire ring terminals from the studs.

Figure 12. HVIL Circuit Card – Four (4) Mounting Nut/Washer Locations (M5)

7. Using a Torx PlusTM T25 bit, remove the four (4) M5x30mm screws securing the HVIL Circuit Card as
shown in Figure 13.

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SIL 3­EP­16
January, 2016
Page 10 of 31

Figure 13. HVIL Circuit Card – Four (4) Mounting Screw Locations (M5x30mm)

8. Using a Torx PlusTM T25 bit, remove the two (2) M5x14mm screws securing the HVIL Circuit Card as
shown in Figure 14.

Figure 14. HVIL Circuit Card – Two (2) Mounting Screw Locations (M5x14mm)

9. Using a Torx PlusTM T25 bit, remove the four (4) M5x22mm screws securing the HVIL Circuit Card as
shown in Figure 15.

Figure 15. HVIL Circuit Card – Four (4) Mounting Screw Locations (M5x22mm)
10. Lift the HVIL Circuit Card straight up and remove it from the DPIM Housing.
11. Verify that the choke is in place as shown in Figure 16.

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SIL 3­EP­16
January, 2016
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NOTE: The choke may have adhered to the underside of the HVIL Circuit Card when it was removed. If
this has occurred, reinstall choke to its proper location as shown in Figure 16. The choke must be installed
with the arrow pointing toward the DC lug box.

(1)

–

Choke

Figure 16. Verification of Choke Installation

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 3­EP­16
January, 2016
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Section 2: Removal of BCA Card Mounting Shelf
1. As required, carefully cut and remove the wire ties retaining the wire harnesses (refer to Figure 17).

Figure 17. Wire Tie Locations

2. Remove five (5) wire harness connectors from circuit card surface mount connectors by gently depressing
the retaining tab with a pick or small flat blade screwdriver (refer to Figure 18 and Figure 19).
NOTE: Use care to avoid bending or damaging the circuit card connectors.

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SIL 3­EP­16
January, 2016
Page 13 of 31

Figure 18. Wire Harness Connector Removal (4 Locations)

Figure 19. Wire Harness Connector Removal

3. Using a Torx PlusTM T25 bit, remove the seven (7) M5x14mm screws securing the BCA Mounting Shelf
(refer to Figure 20).

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 3­EP­16
January, 2016
Page 14 of 31

Figure 20. BCA Mounting Shelf Fastener Locations

4. Carefully lift the BCA Mounting Shelf and set in on the side of the chassis as shown in Figure 21.
NOTE: Three (3) harnesses are still connecting the BCA Card to the GATE Drive Cards. Do NOT relocate
the BCA Mounting Shelf any farther than as shown in Figure 21.

Figure 21. BCA Mounting Shelf (GATE Drive Card Cable Connectors Shown Circled)
5. Remove three (3) ribbon cable connectors from the GATE Drive Cards (refer to Figure 21) as follows:
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SIL 3­EP­16
January, 2016
Page 15 of 31
a. Use the handle of Tab Bending Tool J­51586 to disengage and remove the cable strain relief cap
(refer to Figure 22).

Figure 22. Cable Strain Relief Cap Removal (BCA Cable Card Connector Shown for Clarity)
b. Press the tabs down on both sides of the GATE Drive Card Connector to release the ribbon cable
connector (refer to Figure 23).

Figure 23. Releasing the GATE Drive Card Cable Connector (BCA Cable Card Connector Shown for Clarity)

6. Remove the BCA Mounting Shelf from the DPIM to gain access to the three (3) Current Sensors.

Copyright © 2016 Allison Transmission, Inc. All Rights Reserved.

SIL 3­EP­16
January, 2016
Page 16 of 31

Section 3: Removal of the AC Busbar Assembly and AC Terminal Block
NOTE: Refer to Figure 24 for DPIM2 Phase Locations.

Figure 24. DPIM2 Phase Locations

1. Using a Torx PlusTM T25 bit, remove the six (6) M5x22mm screws (refer to Figure 25).

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SIL 3­EP­16
January, 2016
Page 17 of 31

Figure 25. Mounting Screw Locations

2. Using a 6mm hex key, remove the three (3) M8 AC lug bolts (refer to Figure 26).

Figure 26. AC Lug Bolts

3. Remove the HVIL switch connector (refer to Figure 27).