735B, 740B and 740B EJECTOR Articulated Trucks Chassis Electronic Control System Caterpillar

Interaxle Lock Supply Pressure Is Low

Usage:

735B L4D

Use this procedure to troubleshoot low pressure at the Inter Axle Lock Supply or use this procedure if the following event code is active. Refer to Troubleshooting, "Event Codes List" in this manual, for information about other chassis event codes.

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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
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

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^( 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 pressure

Recommended Actions

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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 Relief Solenoid Valve. An electrical problem could also be involved. Other possible causes are a stuck Inter Axle Lock Main Relief valve or a fault with the OTG supply pump. Note: The 356-5145 Main Relief Valve and the 295-8358 Output Transfer Gear Oil Relief Solenoid Valve are located on the 386-9746 IAD control valve body. The valve body is located on the OTG housing.