If your car's automatic transmission is locked to a single gear and your engine won't rev up fully, your transmission may be stuck in safe mode. Safe mode is a feature in modern automatic transmissions that helps prevent damage to your transmission or engine when the computerized transmission control module in your car detects that something may be wrong.
Driving around in safe mode for long periods isn't recommended, since you won't be able to fully accelerate. If your transmission is in safe mode, you'll need to take your car to a transmission repair shop to have it inspected. To learn more about what safe mode does and what you should do if your transmission is stuck in safe mode, read on.
What Is Transmission Safe Mode?
A car with an automatic transmission has a computerized transmission control module that constantly monitors engine and transmission data fed to it by numerous sensors. If one of these values is missing due to a faulty sensor or is out of range due to a problem in the engine or transmission, the transmission control module will immediately engage the transmission's safe mode. You won't be able to shift gears, and you won't be able to give full power to the engine.
The primary purpose of safe mode is to prevent your transmission from being damaged and to keep you safe on the road. If the transmission control module can no longer measure the engine speed due to a faulty sensor, for example, it will immediately engage safe mode — without the engine speed, the automatic transmission doesn't know when to shift gears, and shifting gears at the wrong time can damage the engine or transmission.
In addition to faulty sensors, mechanical problems in your transmission can also turn on safe mode. For example, if your transmission fluid has a large amount of metal or rubber contaminants in it due to your transmission components deteriorating, this will increase friction while shifting and cause your transmission fluid to heat up. When the temperature of the transmission fluid climbs above the manufacturer's suggested range, your car's computer will engage in safe mode to prevent you from using your transmission and potentially cause more damage to it.
What Should You Do When Your Transmission Is Stuck in Safe Mode?
If your car's transmission is in safe mode, you need to take it to a transmission repair shop as soon as possible. You'll still be able to drive your car while it's in safe mode, but you'll be limited to very low speeds. You should only drive your car to the transmission repair shop if it's close to your home and if there are no roads with fast-moving traffic along the way. Driving much slower than the traffic around you is a safety hazard, so it's better to have your car towed if you'd need to take a highway or major thoroughfare to get to the repair shop.
Once at the transmission repair shop, a technician will check the error codes on your car's computer to determine what's causing your transmission to go into safe mode. These error codes can tell the technician if a sensor isn't sending any data, which means that a faulty sensor is likely causing the problem. They can also tell the technician which sensor values are out of range, which will help them determine if a mechanical problem within your car's transmission is causing it to enter safe mode.
Overall, the safe mode feature in your car is an important feature that can help protect your transmission from further damage by limiting your ability to use it. Repairing transmission problems early helps you save money since it can allow you to avoid replacing your entire transmission. If your car's stuck in safe mode or enters it intermittently, take your car to a transmission repair shop so that it can be inspected and fixed.