509
Thermo King
Critical

ECU Failed to Enable

The unit failed to enable or turn on the engine ECU following the logic sequence.

Possible causes

  • Blown ECU fuse
  • Defective engine power relay
  • ECU power wiring failure
  • Insufficient battery voltage for startup

Recommended actions

  • Check fuses and relays associated with the ECU
  • Measure supply voltage at ECU input pin
  • Inspect engine ground connections
  • Verify battery charge and health

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