35668-ZY6-003 Honda SENSOR, AIR FUEL RATIO (Honda Code 7635121).

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 can only be administered after a failure occurs. The decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS5380" as the Part Number and "7755" as the Group Number. Use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.
Termination Date
March 31, 1999Problem
Two-way communication devices emissions have caused unexpected engine speed variation ( 100 rpm) due to interference with the electronic controller.
A flickering monitor panel is not related to interference with the controller and will not be addressed in this service letter.
Affected Product
Model & Identification Number
Group 1
M312 (6TL169-296)
M315 (7ML464-601, 7ML603, 7ML604)
M318 (8AL764-913, 8AL915, 8AL918 6ES1-220 )
Group 2
M312 (6TL1-168)
M315 (7ML1-463)
M318 (8AL1-763)
Parts Needed
Action Required
Replace engine control only when needed. See the attached Rework Procedures for Groups 1 and 2.
Service Claim Allowances
Group 1 or 2
This is a 1-hour job.
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
Attach.(1-Rework Procedure)Rework Procedure
Before replacing the engine control, check all communication devices (only customer installed devices) for proper installation. A repair of antenna components (except factory installed devices) may very likely solve the problem without the need for replacement of the engine control.
Following are some points to be checked before the engine control is replaced:
- Ensure antenna cable (except factory installed) is a 50 ohm coaxial (HF) cable.- Check the shielding of antenna (except factory installed) for any short radius bending or damage.- Check communication device and antenna (except factory installed) are properly connected (wire and shield).- Check communication device and antenna (except factory installed) are properly grounded.Do not replace the engine control, if the above antenna repairs solved the problem.
Group 1 Rework (Illustration 1)
1. Removal of Engine/Pump Controller:Adjust the seat so that you can easily reach both electronic controllers (1'and 2)
Disconnect the engine/pump controller connector.
Loosen the two bolts (a) holding the engine/pump controller (1') to support (3).
Disconnect the housing ground wire (7) and remove the engine/pump controller (1').
2. Removal of Engine Control (2):Loosen the four bolts (b) fastening engine control (2) housing to support (4).
Disconnect housing ground wire (7).
Disconnect the connector by loosening bolt (c) with a 4 mm allen wrench.
Remove engine control (2).
3. Installation of the new 1439581 Engine Control (2):Install connector to the new engine control (2) with 4 mm allen head bolt (c).
Connect housing ground wire (7).
Install new engine control (2) with four bolts (8) to support bracket (4).
4. Installation of Engine/Pump Controller (1'):Install engine/pump controller (1') on support (3).
Connect housing ground wire (7).
Install connector onto engine/pump controller (1').
If the engine control can be easily replaced without removing the engine/pump controller, skip steps 1 and 4.
Group 2 Rework (Illustration 2)
Removal of Engine/Pump Controller: (1')
Adjust the seat so that you can easily reach both electronic controllers (1' and 2')
Disconnect the engine/pump controller connector.
Loosen the two bolts (a) holding the engine/pump controller (1') to support (3').
Disconnect the housing ground wire and remove the engine/pump controller (1').
Removal of Engine Control (2'):
Loosen the bolt (b) off the engine control fastening plate (4').
Disconnect the engine control connector by loosening bolt (c) with a 4 mm allen wrench.
Disconnect the housing ground wire and remove engine control (2').
Removal of Plate (3'):
Loosen the two bolts (d) from plate (3') and disconnect all the ground wires.
Pull plate (3') as far as you can to allow access to bolts (e) of the PDT connector.
Remove the PDT connector by loosening the 4 bolts (e).
Installation of the new 1357608 Plate (3): (Illustration 2)
Re-install PDT connector on new plate (3) with bolts (e).
Install new plate (3) with the two bolts (d).
Installation of the new 1439581 Engine Control (2):
Install new engine control (2) on new 1395317 Plate (4) with 8T3844 Bolts (8) and 9X8256 Washers (6).
Connect the engine control connector with the 4 mm allen head bolt (c).
Fasten assembly (2-4-6-8) to plate (3) with 8T4171 Bolts (5) and 9X8256 Washers (6).
Connect the longest wire of 1398284 Wire Assembly (7) to the engine control housing.
Installation of Engine/Pump Controller (1'):
Re-install engine/pump controller (1') onto plate (3) with bolts (a).
Connect the shortest wire of 1398284 Wire Assembly (7) to engine/pump controller (1').
Re-install engine/pump controller connector.
Illustration 1
Illustration 2