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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