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

Interaxle Lock Supply Pressure Is High

Usage:

735B L4D

Use this procedure to troubleshoot high Inter Axle Lock Supply Pressure 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.

Note: Under the conditions outlined in this section of the manual, the truck can be started but should not be driven. Driving the truck with this fault active may result in damage to the Output Transfer Gear. Lubrication to the Output Transfer Gear may be reduced.

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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
E1501 (2) High Inter Axle Lock Supply Pressure	· Inter Axle Lock Supply Pressure Sensor signal is higher than expected. Inputs used in the software mapping for E1501 are: · Interaxle Lock Solenoid (must be "ON"). · Engine Speed (RPM). · Output Transfer Gear (OTG) Oil Temperature	· ATC will be disabled for the Inter Axle Differential Lock subsystem. · ATC ⁽¹⁾ lamp on the main cluster display 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 Multi-Purpose Display (CMPD)

Probable Causes

A blockage or mechanical failure in the Inter Axle Differential Lock subsystem (OTG hydraulics).
A stuck Output Transfer Gear Lube Oil Relief Solenoid Valve.
A failed Inter Axle Lock Supply Pressure Sensor.

Recommended Actions

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Table 2
Interaxle Lock Supply Pressure Is High
Troubleshooting Test Steps	Results
1. Check For Codes A. Connect Cat^® ET to the truck. B. Determine how many E1501 events codes have occurred and when the last event occurred. C. Check and address any related diagnostic codes. D. Clear the E1501 event and operate the truck in the same manner as when the event was triggered, to see if the event returns.	OK - Event code E1501 is not present or does not return, however a related diagnostic code is present. Troubleshoot any related codes before continuing with this procedure. NOT OK - E1501 code remains present. Proceed to Test Step 2.
2. Check For A Blockage In The Output Transfer Gear (OTG) Hydraulics A. Check for any blockage or mechanical failure in the Output Transfer Gear Lube Oil Relief Valve. Also check the OTG cooler and cooler hydraulic lines, or the Thermal Bypass Valve at the OTG cooler. Refer to Testing and Adjusting, UENR0205, "Power Train Pressures".	OK - No blockage found in the OTG hydraulics. Proceed to Test Step 3. NOT OK - A blockage has been located in the OTG hydraulics. Repair: Clear and clean the blockage. Perform the necessary repairs. If the problem is not resolved, proceed to Test Step 3.
3. Check For A Stuck Output Transfer Gear Lube Oil Supply Solenoid A. Perform the ATC System Pressure checks for the Inter Axle Differential Lock Supply pressure. Note: Do not override Inter Axle Differential Lock clutch current (leave at zero amps). Refer to Troubleshooting for MID 87 - DTC 3543-5 in this manual.	OK - Inter Axle Lock Supply pressure is less than 1000 kPa (145psi). Proceed to Test Step 4. NOT OK - Inter Axle Lock Supply pressure is greater than 1000 kPa (145psi), the Output Transfer Gear Lube Oil Supply Solenoid Valve is malfunctioning. Repair: Perform the necessary repairs. Refer to Disassembly and Assembly, UENR0207, "Solenoid Valve (Differential Lock) - Remove and Install" and Disassembly and Assembly, UENR2351, "Solenoid Valve (Differential Lock) - Disassemble and Assemble". If the problem is not resolved, proceed to Test Step 4
4. Check for a Failed Inter Axle Lock Supply Pressure Sensor A. Check the operation of the Inter Axle Lock Supply Pressure Sensor 344-7391. The sensor is located on the Inter Axle Differential control valve body. B. Install an accurate pressure gauge at Inter Axle Lock Supply pressure test port. Connect Cat ^® ET and monitor the Inter Axle Supply pressure while comparing to the gauge reading. Refer to Troubleshooting procedure MID 87 - DTC 3542-8 in this manual.	OK - The reading from the Inter Axle Lock Supply Pressure Sensor and the gauge are the same, the sensor is working properly. STOP NOT OK - The reading from the Inter Axle Lock Supply Pressure Sensor and the gauge are NOT the same, the sensor is faulty. Repair: Replace the faulty sensor. If the problem is not resolved, contact the Technical Communicator at your dealership for possible consultation with Caterpillar.