Why is over drive light coming on in 1990 Toyota Celica?

The overdrive light in a 1990 Toyota Celica may illuminate due to a few potential issues. It could indicate that the overdrive function is disabled, often due to a malfunctioning transmission or a problem with the overdrive switch. Additionally, low Transmission Fluid levels or a faulty speed sensor could trigger the light. It's advisable to have the vehicle inspected to diagnose and resolve the underlying issue.