COVER 1023479 - Caterpillar

(E1677/E1678/E1679) Cross Axle Lock Clutch Accumulated Thermal Energy
Use this procedure to troubleshoot an active E1677, E1678, and E1679 event codes. Refer to Troubleshooting, "Event Codes List" in this manual, for information about other chassis event codes.
Table 3
List of Event Codes (EID) For the Chassis ECM (MID 87)
Code (Level) and Description Conditions which Generate this Code System Response
E1677 - High Center Cross Axle Lock Clutch Accumulated Thermal Energy
E1678 - High Front Cross Axle Lock Clutch Accumulated Thermal Energy
E1679 - High Rear Cross Axle Lock Clutch Accumulated Thermal Energy
Activates - When the ECM estimated temperature in the Cross Axle Differential lock clutch of the axle indicated is higher than 220° C (428.0° F) .
Inputs - Speed Sensors
Cross Axle Lock Solenoid
Deactivates - When the estimated temperature is lower than 140° C (284.0° F).
ATC will be disabled for the particular axle indicated.
ATC lamp will not light. Probable Causes
Low Cross Axle Lock Clutch pressure.
Mechanical Failure of the Cross Axle Lock Solenoid.
Low supply pressure from the Pressure Reducing Valve.
Incorrect wheel speed sensor gap, due to loose mounting bolts.
Mechanical failure of one of the axle wheel speed sensors (two speed sensors for each axle).
Failure of the Cross Axle Differential clutch.
Broken axle shaft.Recommended Actions
Table 4
Frequent "High Cross Axle Lock Clutch Accumulated Thermal Energy - E1677, E1678, and E1679" Events
Troubleshooting Test Steps Results
1. Check Cat ET for any faults or events related to ATC, such as a faulty wheel speed sensor or wheel speed mismatch and correct.
OK - Other ATC faults or events logged and corrected, problem resolved.
On rare occasions, the E1677, E1678, E1679 events will not automatically de-activate. The fault may have activated due to an E1248, E1249, or E1250 Cross Axle lock mismatch event. If so resolve this Cross Axle lock mismatch event first before proceeding to troubleshoot the E1677, E1678, E1679 events.
NOT OK - Other ATC faults or events logged and corrected but problem is not resolved.
Repair: Proceed to Test Step 2.
2. Check the Cross Axle Differential Clutch Pressure.
Refer to:
System Operation/Testing & Adjusting, M0082312, "730 and 735 Articulated Trucks Machine System Operation/T&A" manual for more information.System Operation/Testing & Adjusting, M0082320, "730 Ejector Articulated Trucks Machine System Operation/T&A" manual for more information.
OK - Pressure to the Cross Axle Differential Lock clutch is correct ( 4000 400 kPa (580 58 psi).
Proceed to Test Step 3.
NOT OK - The Cross Axle differential clutch pressure is below specification and/or the Cross Axle differential clutch pressure increases slowly or is erratic.
Proceed to Test Step 4.
3. Check integrity of the wheel speed signals.
A. Connect Cat® ET to the truck
B. Record all wheel speeds. (record at highest sample rate)
C. Drive truck in a straight line on a solid dry surface where wheel slip will not occur. (do not turn truck) OK - Both the left and right wheel speeds on the problem axle are the same as the rest of the wheel speeds and do not vary from the average speeds.The Cross Axle Differential Lock clutch may have failed or the internal oil supply line in the differential is