BASE 6N0953 - Caterpillar

The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.
This Program must be administered as soon as possible. When reporting the repair, use "PI3780" as the Part Number, "7751" as the Group Number, "56" as the Warranty Claim Description Code and "T" as the SIMS Description Code. Exception: If the repair is done after failure, use "PI3780" as the Part Number, "7751" as the Group Number, "96" as the Warranty Claim Description Code, and "Z" as the SIMS Description Code.
This Revised Service Letter replaces the July 7, 1995 Service Letter. Changes have been made to the Affected Product.
Completion Date
January 31, 1996Termination Date
July 31, 1996Problem
The timing map of the existing engine control group (personality module) on certain 776B and 776C Tractors and 777B and 777C Trucks may advance the timing too far resulting in an excessive rate of rise in the cylinder pressures which could contribute to piston ring failures.
Other factors, such as engine oil condition due to extended oil change periods or using CD or CE oil can also contribute to piston ring failures.
Affected Product
Model & Identification Number
776C (2TK1-86)
777C (4XJ79-779)
This Program also applies to remanufactured engines 5TL1-120 in dealer exchange and new engines 7YG1-1315 in dealer exchange.
This Program also applies to 776B Tractors (S/N 6JC1-up), 777B Trucks (S/N 4YC1-up) and dealer exchange engines 99W1-up and 4ZL1-up that have been fitted with the electronic fuel injection system in the field.
Parts Needed
Dealers will need to order parts for this Program.
1 - 3E3370 Receptacle Assembly1 - 3E3371 Wedge1 - 1036091 Sensor Assembly1 - 1248690 Control GroupAction Required
Installation procedures for the new control group are packaged with the new 1248690 Control Group.
Owner Notification
U.S. and Canadian owners will receive the attached Owner Notification.
Service Claim Allowances
This is a 2-hour job.
U.S. and Canadian Dealers Only - Eligible dealers may enter a Type 2 SIMS Report.
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
MAKE EVERY EFFORT TO COMPLETE THIS PROGRAM AS SOON AS POSSIBLE.
Attach.(1-Owner Notification)Copy Of Owner Notification For U.S. And Canadian Owners