If the O/D Off light is on and not blinking or flashing, it is SAFE to drive any further you like. I guess you or someone has pressed the O/D button on the gear stick, which turned the light on. The light, in this case, does not pose any drivability concerns or mechanical issues to your vehicle. The only downside to having it on is poor fuel economy and more noise at higher speeds.
The case is very different when the illuminated light is blinking or flashing regularly. In such a case, it may indicate a problem with your transmission that should be fixed as soon as possible. You will be able to diagnose and fix this problem by recording the diagnostic trouble codes stored by your vehicle’s onboard computer by using a transmission code reader.
It should be noted that the transmission is a delicate component in your car and should never be fixed by an inexperienced person. If you notice that there is a stored code related to the transmission, then make sure to take your car to the nearest mechanic shop to have it checked out. You may be able to drive the car for some time without fixing the issue, but that is risky since it will lead to more complications, hence more expenses.
If your light isn’t blinking and it is just on, then you can proceed to turn off the overdrive light by locating the overdrive button.
What does the O/D Off light mean?
The O/D Off light will turn on if you switch the overdrive function off. The O/D Off light means that your vehicle has disabled the overdrive functionality and hence your transmission cannot shift to the highest gear to facilitate acceleration on an upgrade or deceleration on a downgrade.
When the O/D Off light is on, you will be able to keep your vehicle in one gear so that you can have more manual control over your driving. This is useful in bad weather conditions when you need to be careful and precise with the maneuverability of your car.
Most automatic vehicles from Japan such as Toyota have the overdrive switch to help in switching between the usual four gears. In their cases, they won’t be able to engage the fourth gear when the overdrive is off but can be able to switch between the other three gears. You should make sure the O/D Off light is never on if you want your transmission to shift to the fourth gear to help with fuel economy.
The O/D Off light is useful when you want to help the onboard computer decide on which gear to select. This is usually the case when you are carrying a heavy load such as towing a trailer. In this case, the automatic transmission will try to shift back and forth between overdrive and the following highest gear to find a suitable speed.
Switching off the overdrive function will help your vehicle make a better decision regarding the driving speeds, engine revolutions, and gear selection. It is also favorable to let the O/D Off light stay on if you prefer engine braking when going downhill.
What is O/D?
O/D is an abbreviated short form that means Overdrive. The overdrive is a functionality that has been present in many vehicles since 1934. A lot of people confuse the term to mean an increase in speeds and incredible boosts in performance. However, overdrive serves another purpose that doesn’t necessarily entail faster speeds.
Overdrive is a feature that helps in automatically controlling the speeds of your vehicle by providing sustainable speeds at lower engine RPMs (Revolutions per minute). Having the overdrive on will enable you to have better fuel consumption by making the driveshaft turn faster than the engine. Overdrive also helps in reducing wear and tear of components and also lowering the noise produced by the car.
The overdrive chooses the highest gear in your vehicle to achieve its functions. This means that your car will be over-geared when the overdrive is on. The engine turns faster with higher RPMs when you select a lower gear, the opposite happens when in overdrive. An engine will produce fewer revolutions when the transmission is over-geared, thereby controlling the vehicle’s potential top speeds.
Modern vehicle computers use this function to estimate when your vehicle needs to be put in overdrive. You will often not need to manually use it since the vehicle will automatically kick in to adjust your speeds and make use of the overdrive feature.
What does the O/D button do?
The O/D button stands for the overdrive button/switch. It is located on the side of your gearshift and it is usually a small push-button with the O/D letters inscribed on it or close to it. The O/D button is used to engage or disengage the overdrive functionality. Switching it on turns off the overdrive, while switching it off will engage the overdrive.
To turn on the O/D Off light, you will have to switch on the O/D button to make sure your vehicle does not kick into overdrive. The opposite is the case when you want to engage the overdrive function.
When you press the O/D button, the automatic transmission will kick in to disengage the highest gear completely. Your vehicle is then left with the rest of the gears that the system can now interchange to give you better traction but poor fuel economy.
Most modern vehicles can correctly and intuitively switch between an overdrive mode and a non-overdrive mode. The onboard controller is fitted with lots of data and conditional instructions to make sure to turn O/D off at the right time. The inclusion of the O/D button is usually for peace of mind and convenience, however, most of the time you won’t have a reason to use it.
When should you use the O/D button/turn off overdrive?
The O/D button will be used mostly for towing a trailer. Towing a trailer is one of the few circumstances that your vehicle will be heavily loaded to the point where the onboard controller won’t be of much help.
The controller will still try to switch to the highest gear even when your vehicle is carrying heavy loads. You do not want it to do that since the clutches and other transmission parts may get damaged or locked due to the weight. In this scenario, you can utilize the O/D button to lock out the transmission out of overdrive to prevent wear, tear, and loud noises from the moving parts.
Apart from towing a trailer, here are other instances that may benefit from turning off the O/D functionality:
- Driving down a steep hill – turning the O/D off allows for engine braking to help slow down the vehicle. This prevents the use of brakes that would otherwise be heated excessively by going down the steep hill.
- Driving up a steep hill – O/D off ensures the engine stays in the next highest gear to provide enough climbing torque.
- Driving in terrible weather conditions such as winter – O/D off ensures better traction to avoid losing control.
For those vehicles with cruise control, you will want to first cancel the cruise control before turning off the overdrive. The reason for switching off the cruise control is because the engine cannot brake if cruise control is on.
For you to enable the engine braking, you will have to stop the cruising mode, and then you will be able to turn off the overdrive which will, in turn, enable engine braking. It is important to note that not all vehicles will need for this, make sure to check your manual for more information.