Why Your O/D Off Light Is On

What does O/D Off mean in a car?

O/D Off means your car’s Overdrive is disabled. Overdrive is a feature you only find on cars with an automatic transmission that were manufactured earlier than 2017 or so. The “O/D Off” indicator is simply letting you know that the Overdrive feature is disabled—probably because you accidentally tapped the button. The button to turn the Overdrive on and off is typically located on the gearshift. People accidentally tap it all the time—especially on Nissans, Infinitis, Volkswagons, and Audis (which seem to have sensitive O/D buttons).

What does Overdrive do?

Overdrive improves fuel economy by locking out higher gears. When overdrive is active, your transmission is not allowed to move into the highest gears. Lower gears provide more power but less speed, while higher gears provide less power but more speed. Because the highest settings aren’t very efficient, Overdrive prevents your car from wasting gas when you’re driving at high speeds. To be more specific, Overdrive reduces the rotational speed from the input shaft of the engine so that the engine burns less gas. This dramatically reduces the torque of your vehicle, but if you’re driving fast on a highway you don’t need that torque anyway—your tires aren’t encountering a ton of resistance at high speeds. As a consequence, your car will feel easier to drive and you’ll burn less fuel. Gears 1-3 are typically accelerating gears you’d use to power the car forward, while 4th gear is the cruising speed. Overdrive typically disables 4th-5th gear, which kicks on when you're driving faster at a stable speed.

Can you drive with the O/D Off light on?

Yes, an O/D Off light will not damage your car or prevent safe driving. A flashing O/D Off light is a different ball game, but if the light is solid then your car is just informing you that the Overdrive feature is disabled. This won’t do any harm to your car, although you may need to refill the gas tank slightly faster than you normally would if you’re on a road trip.

How to Turn Off the O/D Off Light

Press the Overdrive button on your gear shift. This button is typically on the smaller side and flush with the rest of your stick shift. Press this button while your car is on and it should turn the Overdrive setting back on. On some vehicles, the Overdrive button is on the dashboard (probably close to the steering wheel). There is no universal symbol for the Overdrive feature, but any button with a caret (^) is likely to be your Overdrive Off/On button.

When to Use Overdrive

Leave the O/D on if you’re just generally cruising. Realistically, it’s going to be rare that turning Overdrive off is really beneficial. Most of the time, restricting your transmission to the lower gears will just save you gas money. If you’re not driving under some unique circumstances, there’s no good reason to shut the feature off. Overdrive does make handling a little easier and more comfortable at high speeds, but most drivers won’t notice a big difference.

Keep O/D off if you’re driving fast on rough terrain. If you’re in a rural area or driving on roads that aren’t pristine, the extra torque in the higher gears may be necessary to avoid skidding off the unfinished roads. The torque you give up at high speed could ultimately be the difference between sliding off a corner at high speeds and perfectly cutting the turn.

Shut the O/D off if you’re on a hilly or mountainous highway. If you’re driving on any kind of hilly or mountainous terrain, losing the torque from Overdrive will make driving more difficult, not easier. The torque will help keep your vehicle stable as you go up inclines and down declines. Without the Overdrive off, your ride might feel a little “looser” than you’re used to. This could potentially be dangerous, especially if it’s raining or very windy out.

Why would the O/D Off light be flashing?

A flashing O/D Off light indicates a serious transmission problem. You can keep driving slowly, but take the car to a reputable mechanic to have them inspect your transmission. A flashing O/D Off light indicates that the transmission isn’t shifting into the Overdrive gears when it is supposed to. Do not ignore this problem, as it may cause damage to your transmission. This can be caused by a bad transmission speed sensor, a bad transmission solenoid, or a physical defect in your transmission’s gearbox. This is most likely to happen on Ford vehicles. Other makes and models do not rely on the O/D indicator to communicate transmission issues.