• Determines how much fuel to inject
• Ensures the correct air–fuel mixture

2. Ignition Timing

• Controls when the spark plug fires
• Optimizes power and fuel efficiency

3. Air Intake Management

• Adjusts airflow into the engine
• Works with throttle systems

4. Emissions Control

• Reduces harmful gases
• Works with systems like catalytic converters and sensors

5. Engine Monitoring

• Detects faults or problems
• Turns on the check engine light if needed

• The warning light may:
  • Stay on constantly
  • Come on with no clear reason

2. Engine Performance Problems

• Rough idling
• Loss of power
• Engine hesitation or stalling

3. Difficulty Starting or No Start

• Engine takes long to start
• Or doesn’t start at all

4. Poor Fuel Efficiency

• Sudden increase in fuel consumption

5. Engine Misfires

• Jerking or uneven running
• Misfire codes may appear

6. Transmission Issues (in some vehicles)

• Hard or erratic shifting

In many vehicles, ECM works with transmission control

7. Increased Emissions

• Failing emissions test
• Black smoke (in diesel engines)

8. Electrical Problems

• Sensors showing incorrect readings
• Random fault codes
• Loss of communication with diagnostic tools

9. Intermittent Problems

• Issues come and go randomly