Water Delivery System and 777F WTR, 777G WTR and 785D WTR OEM Off-Highway Trucks Caterpillar

Hydraulic System Oil Level Is Low

Usage:

785D DMC

This message occurs when the signal from the WDS hydraulic oil tank level sensor indicates that the oil level is below the safe operating level. Along with a message a continuous audible alarm is also activated.

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Illustration 1	g03643961

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Illustration 2	g03643962

The possible causes of this diagnostic code are listed below:

Low oil level
Failed pull-up resistor
Broken harness
Failed level sensor

Check WDS Hydraulic Tank Oil Level
1. Park the machine on level ground.
2. Turn key start switch to the OFF position.
3. Observe the oil level on the sight glass on the WDS hydraulic tank.
4. Check for hydraulic oil leaks.
  Expected Results: Oil level is within range indicated on sight glass.
  Results:
  OK - The oil level is within range. Proceed to Step 2.
  Not OK - The oil level is low.
  Repair: Add hydraulic oil. Check for the error code.
  Note: If the oil is too low in the tank or the tank is empty, the hydraulic system most likely contains a large leak. In the event of a large leak and the tank is fully empty, there is a possibility of severe damage to the hydraulic components. Check the WDS oil filter for any debris, and inspect all WDS hydraulic components. Identify the leak, and repair the leak.
  STOP.
Check WDS Oil Sensor Pull-Up Resistor
1. The machine is still parked with the key switch in the OFF position.
2. Locate the pull-up resistor used for the WDS system. This resistor is located inside the cab. Refer to electrical schematic.
  Expected Result: The resistor measures 1500 ohms.
  Results:
  OK - The resistor measures 1500 ohms. Proceed to Step 3.
  Not OK - The pull-up resistor has failed.
  Repair: Change the resistor.
  STOP.
Check WDS Chassis Harness and Level Sensor
1. The machine is still parked with the key switch in the OFF position.
2. Disconnect the level sensor from the WDS chassis harness.
3. Add a jumper between pin "A" and pin "C" on the harness where the sensor connects.
4. Remove the pull up resistor in the cab, and add jumper wire in place of the resistor.
5. Observe the MD3 display for a diagnostic code.
  Expected Result: The MD3 shows no error message.
  Results:
  OK - The MD3 shows no error message. The level sensor has failed.
  Repair: Change the level sensor. Check for the diagnostic code.
  STOP.
  Not OK - The MD3 still has the low hydraulic oil error.
  Repair: Check the chassis harness wiring X744 for any cuts or breaks. Check for the diagnostic code.
  STOP.