The overdrive (O/D) light on your dash can mean two very different things, depending on whether it is lighting up and staying on, or whether it is flashing or blinking. So, how do you know when you can drive safely and when you can’t?
Here are some things to know about driving with the overdrive:
If the overdrive light comes on and stays on, you have nothing to worry about. All it means is that the overdrive in your car is off. Overdrive is simply a mechanism that allows your car to maintain a steady speed while you are driving, and reduces engine speed by shifting your car into a gear ratio that is higher than the drive gear.
Overdrive improves fuel economy, and makes for less wear and tear on the vehicle when you are driving at highway speeds. Having the overdrive off is fine if you are driving in hilly areas, but if you are on the highway, it is best to have it on because you will get better gas mileage.
To get the overdrive light to turn off, and use your top gear, you should be able to locate a button on the side of your gearshift that will allow you to change the setting.
If your overdrive light is flashing or blinking, you are not going to be able to correct the issue by pushing a button. It means that something is wrong with your car’s transmission – perhaps the range or speed sensors, or the solenoid.
If the overdrive light is flashing, you should have a qualified mechanic come inspect your transmission. When your overdrive light begins to flash, your car’s computer will store a “trouble code” that will identify the type of malfunction that is causing the problem. Once the issue has been diagnosed, we can correct the problems in your vehicle’s transmission.
So, can you drive safely with the overdrive light on? If it is on and not blinking, the answer is yes. If it is blinking or flashing, the answer is "maybe.” Transmission problems should never be ignored, so make sure to get the issue with your overdrive light checked out, and any necessary repairs done.
This article originally appeared on YourMechanic.com as Is It Safe to Drive With the Overdrive Light On? and was authored by Valerie Johnston.