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Toyota Camry: New Battery Problems

This article will examine some of the issues that occur when swapping out the old battery in your Toyota Camry, such as the car still won't start, stalls randomly, or perhaps it idles roughly. We'll address the causes and find some of the solutions.

By August Barrett - August 11, 2015

This article applies to the Toyota Camry 4th, 5th, and 6th generation (1997-2011).

There are several issues which can arise from changing out your old battery with a new one. One of them is that your car has an ECM or engine control module. Your ECM controls several parameters of your engine's electrical operating system, including ignition timing, air-fuel mix, idle and valve timing. It is possible that these were affected when you changed out your battery. There are also several resets that may need to be addressed, like any factory anti-theft or alarm systems that may be preventing your Camry from starting. So let's get to it.

Engine Control Module (ECM) Issues

Rough idling and stalling is most likely the result of poor air-fuel mixture or ignition and valve timing. What has happened is that when you changed your battery out, you have inadvertently reset the engine control module to new settings. But guess what? You can teach your ECM to go back to the way it was before the battery was switched out. To eliminate the low idle and stall issues, take your car out for a nice long drive. One to two hours should do it, or if you don't have time for that long of a drive, several shorter drives should suffice. This will also fix the speedometer pegging out if you're also having that glitch. Does your Camry have a little shake? This may be due to the ignition timing or air-fuel mixture. Several cold starts to a thorough engine warm up should be able to remedy this complication. So, after driving it around for a few days or a week, your ECM should relearn all of your driving habits.

Figure 1. Location of the engine control module.

Alarm Resets

Another dilemma that comes from changing your battery is that now your car may not start. This is probably because your alarm has reset to another setting as well. To get it back on line, first try locking all of the doors with the electronic key lock, and then unlock the driver's side door with the master key. If this fails, look underneath your dash for a toggle switch or push button. When you find it, turn your ignition to the "on" position and then push the button or engage the toggle switch until you hear the alarm chirp. This should reset the alarm setup, and your car should now start.

Figure 2. Alarm toggle switch or push button under the dash.

Installing New Battery

You may be tempted to change out your new battery while the engine is running. This would certainly save you from having any of the reset issues previously discussed, but this is not recommended because you could have a voltage surge and fry out your engine control module. It might just be better to go through the inconvenience of the resetting process than it would be to have to replace the ECM, which can cost anywhere from $100 for a used one to almost 600 bucks for a new one.

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