WHEEL GP-FRONT 6G7877 - Caterpillar

Table 1
List Of Event Codes (EID) For The Chassis ECM (MID 87)    
Code (Level) And Description    Conditions Which Generate This Code    System Response    
E1502 (1) Low Inter Axle Lock Supply Pressure     Activates - when the Interaxle Lock Supply Pressure Sensor signal is lower than expected.
Deactivates - when Inter Axle Lock Supply Pressure Sensor signal is within expected parameters.
Inputs - Inputs used in the software mapping for E1502 are:
Inter Axle Lock Control Solenoid (must be "ON")
Engine Speed (rpm)
Output Transmission Gear (OTG) Oil Temperature     Automatic Traction Control (ATC) will be disabled for the Inter Axle Differential Lock subsystem. Inter Axle Lock Solenoid and the Output Transfer Gear Lube Oil Supply Solenoid are deactivated.
ATC (1) lamp will flash
CMPD (2) warning message displays    
( 1 ) Automatic Traction Control (ATC) lamp is located on the main cluster display
( 2 ) "Colour" Multipurpose Display (CMPD)Probable Causes
Output transmission gear (OTG) oil leak
A stuck Output Transfer Gear (OTG) Lube Oil Supply Solenoid
Stuck Inter Axle Clutch Solenoid
Failed Inter Axle Supply Pressure Sensor
Low OTG hydraulic pressureRecommended Actions
Table 2
Interaxle Lock Accumulator Pressure Is Low    
Troubleshooting Test Steps    Results    
1. Check For Codes
A. Connect Cat® ET to the truck.
B. Determine how many E1502 events codes have occurred and when the last event occurred.
C. Check and address any related diagnostic codes.
D. Clear the E1502 event and operate the truck. Cycle electrical power to the Chassis ECM by turning the key switch OFF and then ON.
Note: Cycle the key switch so the ATC allows the Inter Axle Lock Solenoid and the Output Transfer Gear Lube Oil Supply Solenoid to operate again.     A related diagnostic code is present. Troubleshoot any related codes before continuing with this procedure.
OK - The E1502 event code does not return after related diagnostic codes are corrected.
STOP
NOT OK - The E1502 event code remains active after related diagnostic codes are corrected.
Proceed to Test Step 2.    
2. Inspect For Oil Leakage in OTG Hydraulics.     OK - No oil leakage in the OTG Hydraulics.
Proceed to Test Step 3.
NOT OK - Oil leakage found in the OTG Hydraulics. Perform any necessary repairs.
If the problem is not resolved, proceed to Test Step 3.    
3. Perform The ATC System Pressure Checks Fir Inter Axle Lock Supply Pressure At Various Inter Axle Lock Current Overrides
When reviewing the output for the Inter Axle Lock Supply Pressure Sensor, reference illustration 1.     OK - The Inter Axle Lock Supply pressure is above the fault limit and E1502 is not active.
STOP
NOT OK - Inter Axle Lock Supply pressure is below the fault limit.
Repair: Check for plugged Output Transfer Gear Filter. If the filter is OK, the most likely cause is a stuck 295-8358 Output Transfer Gear Lube Oil