Transmission Light On

Why is the Automatic Transmissions Light On?

Transmission warning lights

Transmission warning lights

In order for modern cars to have smooth gear changes at the right times, the Automatic Transmissions are fully electronically and computer controlled. The device that controls them is called the Automatic Transmission Electronic Control Unit (Automatic Transmission ECU) sometimes called an Automatic Transmission Computer.

The Automatic Transmission computer monitors a wide range of electronic sensors and actuators such as:

  • Automatic Transmission Computer
  • Torque Cover
  • Bands
  • Oil Pump
  • Clutch Packs
  • Automatic Transmission Fluid
  • Hydraulic System
  • Planetary Gear Sets
  • Governor and the Modulator
  • Seals and Gaskets
  • Valve Body
  • Throttle Cable
  • Electrical Solenoids
  • Throttle Position
  • Speed Sensor
  • Electronic Temperature Sensor


If any one of these automatic transmission components is faulty then the automatic transmission computer self diagnostic system while log a fault code into memory, and turn the automatic transmission light on the dash.

Diagnosing Transmission Warnings

At Grimmer Motors our highly experienced, skilled and trusted mechanics have all the latest scan tool technology to read and then diagnose the diagnostic fault code and live data information in your automatic transmission

Please Note: Electronic Tests depend on the vehicle technology and may not be possible on some vehicles.

Call us now to book you car in for a scan, to have us quickly and cost-effectively diagnose and repair your automatic transmission.

Live/work in any of the following areas? Grimmer Motors could be extra convenient for you.Fairfield

  • Fairview Downs
  • Enderly
  • Claudelands
  • Peachgrove
  • Hamilton East
  • Chartwell
  • Chedworth
  • Central Hamilton
  • Forest Lake, Beerescourt
  • Frankton
  • Melville
  • Waikato