ABS Light, Check Engine Light, SRS Light, ESP Light

Dashboard Warning Lights and
the different types of faults.

Dashboard warning lights, ABS, Check Engine Light, Airbag and Traction Control


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Dashboard Warning Lamps

As cars become more advanced to meet regulatory regimes, increasing safety and driver comfort, electronic components have increasingly become an integral part of the modern motor vehicle. Multiple ECU's (electronic control units) are now networked throughout the vehicle constantly communicating with each other. Each ECU is programmed to test itself and the different circuits and sensors it monitors. The dashboard warning lights are there to let the driver know when an ECU has picked up and recorded a fault.

The Different Types of Warning Lights

Not all warning light faults are the same. Some are just to let you know that the door is open, seatbelt is not plugged in or a bulb is blown. Others are more serious they are there to let you know that the fault may be safety, exhaust emission related or can cause serious damage to the car. These faults are can be divided in to several different types. The more important are recorded as a fault code in the relevant ECU and will usually require a Scan Tool to be plugged into the cars diagnostic system. The Scan Tool can then be used to communicate with the relevant ECU and view the fault codes that have been logged.

The Different Types of Faults

Hard Faults

A fault that causes the warning light to stay on permanently. It usually indicates that the fault is occurring now and is caused by something physically broken, like broken wire, actuator or sensor.

Soft Faults

Soft faults can be caused in three ways,

  • Implausibility Faults:

    Caused when then ECU receives information from sensors that cannot possibly be true. For example the car may have two sensors that record vehicle speed. One may say that the car is moving at 50kph while the other recording 80kph. It's unlikely that both are correct so the ECU will turn the warning light on while the fault is occurring and record a fault code.

  • Induced Faults:

    Are caused by something external such as a flat battery. The ECU records that there has been a break in the power supply, turns the warning light on and sets a fault code. These can normally only be reset by a Scan Tool.

  • Intermittent Faults:

    Can be Hard or Soft faults. They can occur on regular occasions or may be months apart. They can be the difficult to trace unless the fault is occurring while the vehicle is in the workshop. But with good equipment, diagnostic procedures and patience these faults are always repairable.

Fault Code Hierarchy

Fault codes also have a hierarchy, the more serious the manufacturer deems the fault can also be indicated by how long the warning light stays on. If the light stay on all the time then the fault is usually serious or it is a hard fault. If the light stays on until the car is switched off, but not when restarted, then a code will have been logged, but the fault is no longer present. And occasionally the warning light will only flash on when driving. All faults occur for a reason, catching the cause early can often prevent serious damage later.

Commonly Used Dashboard Warning Lights

  • ABS,
  • Adaptive Cruise Control,
  • Adaptive Suspension,
  • Air Suspension,
  • Airbag Front,
  • Airbag Side,
  • Airbag,
  • ALB,
  • All Wheel Drive ,
  • AWD,
  • BAS,
  • Battery Charging System,
  • Battery,
  • Brake Fluid Level Indicator,
  • Brake Pedal,
  • Brake Warning Light,
  • Bulb Failure,
  • Catalytic Converter Overheating,
  • Check Engine Light,
  • Clutch Pedal,
  • Coolant Level,
  • Coolant Temperature,
  • Cruise Control,
  • CVT,
  • Diesel Particulate Filter,
  • Diff Lock,
  • Door Open,
  • DPS,
  • Electronic Stability Program,
  • Engine Management Light,
  • ESP,
  • Fuel Filter Water Trap,
  • Glow Plug,
  • Immobiliser,
  • Lane Assist,
  • O/D Overdrive,
  • Oil Level,
  • Oil Pressure,
  • Oil Temperature,
  • Power Steering System,
  • Seatbelt Reminder,
  • Service Light,
  • SRS,
  • Stability Control,
  • TPMS,
  • TPS,
  • Traction Control,
  • Transmission Warning Light,
  • Tyre Pressure Monitor,
  • Washer Level,