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

Interaxle Lock Supply Pressure Is Low

Usage:

Use this procedure to troubleshoot low pressure at the interaxle lock supply or if the following event code is active. Refer to Troubleshooting, "Event Codes" 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 Interaxle Lock Supply Pressure	Activates - when the interaxle lock supply pressure sensor signal is lower than expected. Deactivates - when interaxle lock supply pressure sensor signal is within expected parameters. Inputs - Inputs used in the software mapping for E1502 are: · Interaxle lock control solenoid (must be "ON") · Engine speed (rpm) · Output Transmission Gear (OTG) oil temperature	· Automatic Traction Control (ATC) will be disabled for the interaxle differential lock subsystem. Interaxle 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 on the main cluster display
⁽²⁾	"Colour" Multipurpose Display (CMPD)

Probable Causes

Output transmission gear (OTG) oil leak
A stuck OTG lube oil supply solenoid
Stuck interaxle clutch solenoid
Failed interaxle supply pressure sensor
Low OTG hydraulic pressure

Recommended Actions

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Table 2
Interaxle Lock Supply 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 interaxle lock solenoid and the OTG 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 interaxle lock supply pressure sensor, reference 1.	OK - The interaxle lock supply pressure is above the fault limit and E1502 is not active. STOP NOT OK - Interaxle lock supply pressure is below the fault limit. Repair: Check for a plugged OTG filter. If the filter is OK, the most likely cause is a stuck OTG lube oil relief solenoid valve. An electrical problem could also be involved. Other possible causes are a stuck interaxle lock main relief valve or a fault with the OTG supply pump. Note: The main relief valve and the output transfer gear oil relief solenoid valve are on the IAD control valve body. The valve body is on the OTG housing.