NHTSA ID Number: 10115286
Manufacturer Communication Number: TT8008EN Rev B
TSB/Document Date: 2017-08-16
Summary
Advises service channel to reflash TCM if DTC P2789 is triggered for specific serial numbers
Revisions to this document are noted
by a stripe in the lefthand margin
SUBJECT:
TT8008EN, Rev. B
July, 2017
Page 1 of 6
P2789 Code in School Buses Equipped with Cummins
ISB Natural Gas (NG) Engines
MODELS AFFECTED:
Thomas Built School Buses Equipped with Cummins ISB Natural Gas (NG) and
1000/2000 Series Product Family Pupil Transport Series (PTS) Transmissions
Description of Complaint:
The Check Transmission light can illuminate due to Diagnostic Trouble Code (DTC) P2789 Clutch Adaptive
Learning at Limit in Thomas Built school buses equipped with a 1000 or 2000 Series PTS transmission and a
Cummins ISB Natural Gas (NG) engine. The C3 and C4 clutches may be reported as “Not OK” in the “Trans Health
Indicator” section of the “Prognostics” tab in Allison DOC® Premium.
Cause:
In some cases, the Cummins ISB Natural Gas (NG) engine is reporting engine torque inaccurately. As a result, the
Transmission Control Module (TCM) is unable to accurately adapt the shift causing a shift flare during the 12
and 23 upshifts.
Service Channel Procedure:
In buses where the Check Transmission light illuminates due to DTC P2789, determine if the VIN is included in
Table 1. If included, the authorized Allison outlet will then obtain a field action authorization number. Use Table 1 to
determine the appropriate TCM Assembly number to load into the TCM.
NOTE: Before loading the new TCM Assembly Number into the TCM, make note of the Input and Output
function and Customer Modifiable Constant (CMC) settings.
Use Allison TCM ReflashTM to load the appropriate TCM Assembly Number into the TCM.
Table 1.
VIN
TCM Assembly Number to Load
with Allison TCM ReflashTM
Transmission Serial Number
4UZABRE70HCJB1965
61BR0BU7
6311463632
4UZABRE79HCJB1964
61BR0BU7
6311462758
4UZABRE74HCJB1967
61BR0BU7
6311463685
4UZABRE73HCJB1961
61BR0BU7
6311464029
4UZABRE75HCJB1962
61BR0BU7
6311464383
WBD
3744299
Copyright © 2017 Allison Transmission, Inc. All Rights Reserved.
TT8008EN, Rev. B
July, 2017
Page 2 of 6
Table 1. (cont’d)
VIN
TCM Assembly Number to Load
with Allison TCM ReflashTM
Transmission Serial Number
4UZABRE76HCJB1968
61BR0BU7
6311462970
4UZABRE78HCJB1969
61BR0BU7
6311463303
4UZABRE74HCJB1970
61BR0BU7
6311463344
4UZABRE78HCJB1972
61BR0BU7
6311465517
4UZABRE7XHCJB1973
61BR0BU7
6311466574
4UZABRE71HCJB1974
61BR0BU7
6311467077
4UZABRE73HCJB1975
61BR0BU7
6311467139
4UZABRE75HCJB1976
61BR0BU7
6311467142
4UZABRE77HCJB1977
61BR0BU7
6311467151
4UZABRE79HCJB1978
61BR0BU7
6311467437
4UZABRE70HCJB1979
61BR0BU7
6311467439
4UZABRE77HCJB1963
61BR0BU7
6311463676
4UZABRE64HCJA5853
61BR0BU7
6311469012
4UZABRE72HCJB1966
61BR0BU7
6311463795
4UZABRE67HCJA5863
61BR0BU7
6311469798
4UZABRE76HCJB1971
61BR0BU7
6311465273
4UZABRE62HCJB8729
61BR0BU7
6311485081
4UZABRE6XJCJG6775
61BR0BU7
6311498467
4UZABRE69JCJB3775
61BR0BU7
6311488109
4UZABRE63JCJH9562
61BR0BV1
6311504072
4UZABRE6XJCJH9879
61BR0BV2
6311514424
4UZABRE66JCJH9880
61BR0BV2
6311516554
4UZABRE60JCJD1551
61BR0BV2
6311488234
4UZABRE64JCJD1553
61BR0BV2
6311488824
4UZABRE62JCJD1552
61BR0BV2
6311489108
4UZABRE69JCJH9873
61BR0BV2
6311511392
4UZABRE62JCJH9875
61BR0BV2
6311512395
4UZABRE64JCJH9876
61BR0BV2
6311511421
4UZABRE68JCJH9878
61BR0BV2
6311515019
4UZABRE67JCJH9886
61BR0BV2
6311517330
4UZABRE62JCJH9858
61BR0BV2
6311512957
4UZABRE64JCJH9859
61BR0BV2
6311513175
4UZABRE60JCJH9860
61BR0BV2
6311513192
4UZABRE62JCJH9861
61BR0BV2
6311512151
Copyright © 2017 Allison Transmission, Inc. All Rights Reserved.
TT8008EN, Rev. B
July, 2017
Page 3 of 6
Table 1. (cont’d)
VIN
TCM Assembly Number to Load
with Allison TCM ReflashTM
Transmission Serial Number
4UZABRE64JCJH9862
61BR0BV2
6311513598
4UZABRE66JCJH9863
61BR0BV2
6311513437
4UZABRE68JCJH9864
61BR0BV2
6311513553
4UZABRE6XJCJH9865
61BR0BV2
6311513622
4UZABRE61JCJH9866
61BR0BV2
6311513617
4UZABRE63JCJH9867
61BR0BV2
6311513643
4UZABRE65JCJH9868
61BR0BV2
6311519226
4UZABRE67JCJH9869
61BR0BV2
6311512387
4UZABRE63JCJH9870
61BR0BV2
6311511093
4UZABRE65JCJH9871
61BR0BV2
6311514106
4UZABRE67JCJH9872
61BR0BV2
6311514097
4UZABRE60JCJH9874
61BR0BV2
6311512390
4UZABRE66JCJH9877
61BR0BV2
6311513998
4UZABRE61JCJH9883
61BR0BV2
6311517091
4UZABRE63JCJH9884
61BR0BV2
6311517622
4UZABRE65JCJH9885
61BR0BV2
6311518060
4UZABRE69JCJH9887
61BR0BV2
6311518811
4UZABRE6XJCJH9882
61BR0BV2
6311516947
4UZABRE68JCJH9881
61BR0BV2
6311515566
4UZABRE64JCJE1340
61BR0BV3
6311488230
4UZABRE66JCJE1341
61BR0BV3
6311488138
4UZABRE68JCJE1342
61BR0BV3
6311488694
4UZABRE6XJCJE1343
61BR0BV3
6311488457
4UZABRE62JCJE2857
61BR0BV3
6311492490
4UZABRE64JCJE2858
61BR0BV3
6311492942
4UZABRE64JCJJ4417
61BR0BV3
6311519217
4UZABRE61JCJD4846
61BR0BVV
6311489226
4UZABRE63JCJD4847
61BR0BVV
6311489225
4UZABRE65JCJD4848
61BR0BVV
6311489099
4UZABRE67JCJD4849
61BR0BVV
6311489827
4UZABRE63JCJD4850
61BR0BVV
6311489909
4UZABRE65JCJD4851
61BR0BVV
6311489816
4UZABRE67JCJD4852
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TSB/Document ID: TT8008EN Rev B
Replacement Service Bulletin Number:
MFR Communication Date: 2017-07-11
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: POWER TRAIN:AUTOMATIC TRANSMISSION:CONTROL MODULE (TCM/PCM/TECM)
MFR Component System:
MFR Component Subsystem:
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