Question: I’ve got a newer Toyota minivan and I completely killed the battery a few weeks ago. While I got a new battery, my Sienna has been acting strangely ever since I killed the battery. My fuel mileage is off, and it doesn’t “feel” the same when I drive it. Did I damage my van when I drained the battery?
Answer: Damage? Probably not. But you may have deleted all your Sienna’s engine presets, which can impact both shift patterns and fuel economy. This could make your van feel differently while driving and also reduce fuel economy.
Modern Cars “Learn” And Reprogram Themselves
Most people don’t realize that modern computer-controlled cars are designed to “learn” and reprogram themselves based on driving and usage patterns. If, for example, you tend to accelerate gently when you drive, your vehicle will change the preset shift points to reflect your more leisurely acceleration preference. If you tend to accelerate harshly, the engine computer will reprogram shift points to reflect your emphasis on performance.
The vehicle computer can also change fuel maps based on how you like to accelerate. If you like to race away from stop lights, the computer can put more emphasis on low-end power. If you tend to haul a payload or two a trailer – and push the vehicle really hard on the highway – the computer may change the fuel map to boost mid-range power.
Vehicles can also reprogram themselves based on sensor outputs and how they differ from pre-programmed estimates (due to sensor variances, climate, etc.), etc. The list of items that can change a vehicle’s basic fuel and shift map goes on and on.
What Happens When This Self-Learning Is Lost?
Generally speaking, losing a vehicle’s self-learned programming is not a big deal. If you drain your vehicle’s battery, it will have to “re-learn” all your behaviors and preferences. While the re-learning process can effect fuel economy, or change the way the vehicle feels while driving, it’s not permanent.
This “re-learning” period shouldn’t last more than a few hundred miles. Once you’ve put a couple of tanks of gas in your van, it should be back to normal.
Summing up, there are a lot of good reasons to make sure you vehicle’s battery doesn’t die. Not only will a dead battery be a major inconvenience, but it can also delete programming that effects the way a vehicle drives.