Engine Diagnostics
In order to meet Federal Exhaust Emission and Fuel Economy regulations, today's vehicles are equipped with highly sophisticated electronic engine control systems. These systems do not require periodic adjustments. The only services required on a scheduled basis are spark plug and filter replacement. Tune-ups, as we knew them, are no longer necessary.
Engine Control Computer
The computer receives information from a network of sensors and switches that convert engine operating conditions into electrical signals. Based on the information and instructions stored in the computer program, commands are then sent to three primary systems:
- Ignition System: Spark timing
- Fuel System: fuel injection timing and fuel injection duration
- Emission Control System: Oxygen sensor(s), Evaporation system.
The sensors that monitor one or more of these systems include:
- 1. Mass Airflow Sensor: measures the amount of air entering the engine
- 2. Throttle Position Sensor: Measure the amount of throttle angle
- 3. Manifold Absolute Pressure Sensor: measures the amount of pressure inside the engine
- 4. Coolant Temperature Sensor: Tells the computer the computer temp
- 5. Exhaust Oxygen Sensor: Measures the amount of oxygen in the exhaust
- 6. Crankshaft Position Sensor: Used to tell the computer for top dead in the ignition sequence
- 7. Camshaft Position Sensor: Used to tell the computer for fuel delivery timing.
Computer Control
The computer, sometimes referred to as Electronic Control Unit (ECU) or Powertrain Control Module (PCM), are constantly diagnosing and checking parameters at various sample rates. If a specific parameter does not meet the computers test, then typically the computer will store a check engine light. May not set the check engine light immediately, the test may have to fail a number of times before the check engine light comes on. The check engine light is the computers way of telling the driver, not only there is a problem, but the vehicles is may not be meeting the emission standards.
Car computers are doing more and more in much less time. A car or truck may have more than one computer. When there is more than one computer and they communicate with one another, they are said to be in a network. Sometimes referred to as a LAN Local Area Network. For instance, a Cadillac may have up to but limited to 40 computers in one car. Unfortunately, computers still don't fully diagnose the car, they only point the car technician in the right direction.
