OBD Diagnostics for Engine Braking and Deceleration Fuel Cut-Off (DFCO)

Modern vehicles save fuel during deceleration using Deceleration Fuel Cut-Off (DFCO). OBD engine braking diagnostics allow drivers to confirm when fuel delivery stops and resumes.

How DFCO Works

Fuel Cut-Off During Deceleration

When conditions are met:

• Throttle closed

• RPM above threshold

• Vehicle moving

Fuel injectors shut off completely.

OBD Parameters That Confirm DFCO

Key Indicators

• Injector pulse width drops to zero

• Throttle position closed

• Engine RPM decreases gradually

Common DFCO Issues

• Faulty throttle sensors

• ECU calibration errors

• Improper idle control

Benefits of DFCO Monitoring

• Improved fuel economy

• Reduced brake wear

• Lower emissions

• Better downhill control

Conclusion

OBD diagnostics help drivers confirm DFCO operation and maximize fuel savings.