CCU 001638.00 – Hydraulic Oil Temperature Very Hot

CCU 001638.00 (CCU 1638.00)

Code: 001638.00

Shortcode: 1638.00


This fault code indicates that the Chassis Control Unit (CCU) has detected that the hydraulic oil temperature is at a critically high level, signaling that the fluid is too hot to continue safe operation. High hydraulic oil temperatures can lead to reduced system efficiency, increased wear on components, and potential damage to the hydraulic system.


The function of the hydraulic system is degraded to prevent further damage and ensure the safety of the vehicle. Operating the vehicle with low hydraulic oil levels can also trigger this fault code.


  • Check Hydraulic Oil Level: Ensure that the hydraulic oil level is within the recommended range. Top up if necessary to prevent overheating.
  • Inspect Hydraulic System: Check for any leaks, restrictions, or malfunctions in the hydraulic system that could be causing excessive heat buildup. Repair or replace components as needed.
  • Inspect Transmission Suction Screen: If the fault occurs only during transport speeds, inspect the transmission suction screen for plugging. Clean or replace as necessary.
  • Check Transmission Scavenge Pump: Inspect the transmission scavenge pump for damage. Replace if necessary to ensure proper oil circulation and cooling.
  • Cooling System Maintenance: Ensure that the vehicle’s cooling system is functioning correctly and effectively dissipating heat from the hydraulic system.
  • System Reset and Testing: After addressing the underlying issues, reset the CCU and perform tests to ensure that hydraulic oil temperature remains within safe operating limits under all conditions.


Regular maintenance and monitoring of hydraulic oil temperature are essential to prevent overheating and ensure the reliable operation of hydraulic systems.

Control Units: John Deere

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