How do we ‘talk’ to your car? Through your vehicle’s Engine Control Unit or ECU using dealership diagnostic computers.

So what is an ECU?

An ECU controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by reading values from a multitude of sensors within the engine bay, interpreting the data using multi-dimensional performance maps (called lookup tables), and adjusting the engine actuators accordingly. Before ECUs, air-fuel mixture, ignition timing, and idle speed were mechanically set and dynamically controlled by mechanical and pneumatic means.

The ECU also controls the engine performance for the control of air/fuel ratio and controls the ignition timing. It is also responsible for controlling, amongst other things the variable valve timing and the electronic valve control. In a nutshell it is the ‘brain’ of your car, monitoring performance and engine efficiency and setting off engine warning lights if something is faulting within the engine.

Should an internal fault occur in one of the engine systems, fault codes are stored at the ECU, computerised diagnostic computers engage with the ECU to access these fault codes and identify the fault. The faults are identified by the on-board diagnostics (OBD) of your vehicle, which is an automotive term referring to a vehicle’s self-diagnostic and reporting capability.

When a sensor voltage falls out of specifications, the ECU will illuminate a “CHECK ENGINE, SERVICE ENGINE SOON, OR MAINTENANCE REQUIRED” light at the instrument cluster. The ‘warning light’ means the ECU has received a bad reading from at least one sensor.

OBD systems provide an ability to access the status of the various vehicle subsystems. The amount of diagnostic information available via OBD has varied widely since its introduction in the early 1980s versions of on-board vehicle computers. Early versions of OBD would simply illuminate a malfunction indicator light or “idiot light” if a problem was detected but would not provide any information as to the nature of the problem. Modern OBD implementations use a standardised digital communications port to provide real-time data in addition to a standardised series of diagnostic trouble codes, or DTCs, which allow one to rapidly identify and remedy malfunctions within the vehicle.

Did you know that in 1968 it was Volkswagen who introduced the first on-board computer system with scanning capability, in their fuel-injected Type 3 models.

So what happens is the engine warning light illuminates? Can I take it to an ‘Aftermarket’ workshop rather than the dealership?

The answer to that is simple…you can take your car anywhere that has the correct diagnostic computer to engage and talk to your vehicles’ ECU.

The workshop will engage the relevant diagnostic computer to your make of vehicle and complete a scan to read the OBD computer trouble codes. Once the diagnostic computer has completed a diagnostic test, the relevant trouble code number/s are found and the workshop are able to locate the cause of the fault, like “MAP sensor voltage low” and so on. The diagnostic computer can erase the codes from the ECU and a test drive may be completed on your vehicle. Upon return to the workshop, the ECU is rechecked to find out if the codes has cleared or returned. If it has returned, further investigations may be required.

SVS Autocare are the European Vehicle Specialists on the Sunshine Coast and have the latest computerised diagnostic computers for a range of vehicles, including:

  • Porsche
  • Lamborghini
  • Bentley
  • Mercedes – including AMG models
  • Audi
  • BMW
  • VW
  • Skoda
  • Plus generic diagnostic computers for non-European vehicles.


SVS Autocare proudly care for many prestige European vehicles and are able to provide an extremely high level of service as a proud owner would seek.