725C2, 730C, 730C EJECTOR, 730C2 and 730C2 EJECTOR Articulated Trucks Caterpillar

Interaxle Lock Speed Is Mismatched

Usage:

Use this procedure to troubleshoot interaxle lock speed issues or if the following event code is active. Refer to Troubleshooting, "Event Codes" in this manual, for information about other chassis event codes.

Note: The 730C is equipped with speed sensors on the front and rear axles. On the 725C2/ 730C2 the speed sensors are on the front and center axles.

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Table 1
List Of Event Codes (EID) For The Chassis ECM (MID 87)
Code (Level) And Description	Conditions Which Generate This Code	System Response
E1248 (1) Front Axle Lock Speed Mismatch	Activates - when the ATC detects abnormal left and right front wheel speeds. Deactivates- when event is cleared and ATC detects normal left and right front wheel speeds. Inputs- Differential and axle speed sensors.	· Front cross axle lock will be disabled. · ATC lamp⁽¹⁾ will flash. · Warning message displayed on CMPD⁽²⁾.
E1249 (1) Center Axle Lock Speed Mismatch	Activates - when the ATC detects abnormal left and right front wheel speeds. Deactivates- when event is cleared and ATC detects normal left and right front wheel speeds. Inputs- Differential and axle speed sensors.	· Center cross axle lock will be disabled. · ATC lamp⁽¹⁾ will flash. · Warning message displayed on CMPD⁽²⁾.
E1250 (1) Rear Cross Axle Lock Speed Mismatch	Activates - when the ATC detects abnormal left and right front wheel speeds. Deactivates- when event is cleared and ATC detects normal left and right front wheel speeds. Inputs- Differential and axle speed sensors.	· Rear cross axle lock will be disabled. · ATC lamp⁽¹⁾ will flash. · Warning message displayed on CMPD⁽²⁾.
E1251 (1) Interaxle Lock Speed Mismatch	Activates - when the Automatic Traction Control (ATC) detects abnormal front and rear axle speeds. Deactivates- when event is cleared and ATC detects normal front and rear axle speeds. Inputs- Wheel Speed Sensors	· Inter Axle Differential (IAD) lock will be disabled. · ATC lamp⁽¹⁾ will flash. · Warning message displayed on CMPD⁽²⁾.

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⁽¹⁾	Automatic Traction Control (ATC) lamp is on the main cluster display
⁽²⁾	Colour Multi-Purpose Display (CMPD)

Probable Causes

A stuck interaxle differential clutch solenoid.
Incorrect wheel speed sensor gap due to loose bolts, missing, or broken target ring.
A wheel speed sensor failure.
An interaxle differential lock clutch failure.
A broken drive shaft.

Recommended Actions

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Table 2
Interaxle Lock Speed Is Mismatch
Troubleshooting Test Steps	Results
1. Check For Codes A. Connect Cat^® ET to the truck. B. Determine how many E1251 events codes have occurred and when the last event occurred. C. Check and address any related diagnostic codes. D. Clear the event and operate the truck in the same manner as when the event was triggered, to see if the event returns.	OK - A related diagnostic code is present. Troubleshoot any related codes before continuing with this procedure. NOT OK - E1251 code remains present. Proceed to Test Step 2. Result: E1251 code does NOT return. STOP
2. Monitor The Corresponding Wheel Speed In Cat^® ET A. Connect Cat^® ET and monitor the status screen for the front and rear wheel speeds. B. Drive the truck in a straight line over good/smooth ground conditions and note the wheel speeds.	OK - Wheel speeds are approximately the same and event code is NOT active. STOP NOT OK - Wheel speeds are not approximately the same. Proceed to Test Step 3.
3. Check The Suspect Speed Sensor A. Troubleshoot the speed sensor in question. Refer to the FMI 8 test procedure for the involved speed sensor in this manual. (CID 3531, 3533. 3535, & 3539) B. Check for incorrect speed sensor gap due to loose bolts. C. Ensure that the target ring (chopper wheel) is not missing or damaged. Remove the speed sensor from axle housing. Look through the speed sensor opening & confirm that target ring is in place. NOTE: The truck must be parked on a level surface when removing the speed sensor. If not level, oil may leak out of the speed sensor opening.	OK - Speed sensor problem NOT found and E1251 event code is active. Proceed to Test Step 4. NOT OK - Speed sensor problem found. Target ring is missing or is damaged or speed sensor or circuit was damaged. Repair: Perform the necessary repairs.
4. Perform The ATC System Pressure Checks For The Interaxle Differential Lock Supply Pressure And The Interaxle Differential Clutch Pressure. A. Check the IAD supply pressure and clutch pressure. Refer to System Operation, Testing and Adjusting, "Power Train Pressures".	OK - Interaxle differential clutch pressure and the interaxle lock supply pressure are correct. The interaxle differential lock clutch may be at fault. NOT OK - Interaxle lock supply pressure is correct, but interaxle differential clutch pressure is below specifications. Repair: Check the operation of the interaxle lock solenoid valve. The valve may be sticking or be experiencing an electrical problem. NOT OK - Both the interaxle lock supply pressure and the interaxle differential clutch pressure are low. Repair: Check for plugged Output Transfer Gear (OTG) filter or restriction in the OTG lube pump suction line. If no problems are found, the most likely problem is the output transfer gear lube oil relief solenoid valve. Either the solenoid is sticking or there is an electrical problem with the solenoid. If there is no problem found with the solenoid valve, then the interaxle differential clutch may be at fault. Note: The interaxle lock solenoid valve and the OTG lube oil relief solenoid valve are on the IAD control valve body which is on the OTG housing. Refer to Troubleshooting procedure MID 87 - DTC 3543 in this manual.