Electrical issues after replacing the battery:
Late model vehicles have many computerized systems; in most cases, each system is under the basic control of its own computer (module). There can be more than twenty modules on each vehicle and many of these modules have some sort of "learned" memory, which may be lost when the battery is disconnected. This can cause something minor, like the clock to lose its time, but it can also lead to engine stalling or even a failed smog inspection.
In order to avoid this issue, it has become more and more critical that power is supplied to the electrical system while the battery is disconnected, for any reason, including replacement.
Luckily, there are many "memory saving" devices available that can be connected to the cigarette lighter or the OBDII diagnostic connector. When used correctly, these devices can supply enough power to the modules while the battery is disconnected so they don't lose their memory.
Be sure to follow all manufacturer directions if you use any of these "memory saving" devices. Most of these devices use a small battery to supply power. Opening a door or turning the ignition on with the main battery disconnected can cause the battery in the device to lose power as well.
Examples of how different modules can be affected by loss of battery power:
Door modules: Loss of express-up feature due to loss of stored "pinch point"
Engine control module (ECM, PCM, VCM): Loss of learned idle speed which can cause a stalling condition. Resetting of emission monitors can cause a smog inspection failure.
Power seat modules: Loss of "learned" seat and mirror positions
Radio: Loss of time, radio stations, and possible anti-theft lockout.
Transmission control module: Loss of adaptive information; most late model transmissions "learn" how you drive and "learn" to shift accordingly.
Finding the solution to electrical issues associated with battery replacement:
If you're experiencing electrical issues immediately after a battery replacement or disconnect, make sure the battery cables were reattached and tightened down properly. Herculean strength isn't necessary, but the cables should be snug and not move around or come off of the battery posts. You can also check your owner’s manual for any procedures or drive cycles you can perform to "teach" the car functions it may have lost while the battery was disconnected. If both of those are performed and you're still experiencing issues, your car may require a special computer to re-initialize the modules that lost memory. Check out a local Certified shop near you for more information!
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No start or car is stalling after battery replacement:
In general, it’s not uncommon for late model vehicles to stall after the battery has gone dead or has been disconnected and as we just learned from my friend last Saturday, with a no start your first step should be to make sure those terminals are clean, attached, and tightened!
Another tried-and-tested solution to a no start includes using your car’s spare key to start the car. If this does happen to work, you should take your car back to the dealership and have them reprogram your normal key.
If none of these work and your car still isn’t starting, it could come down underlying issues with your vehicle’s starter, ignition switch, immobilizer system, or the neutral safety switch.
The engine computer has a basic idle speed control setting for when the engine is new. As you drive the car, deposits build up on the throttle body, which restricts the air-flow and reduces the idle speed. The engine control computer compensates for this by opening the idle air bypass valve to achieve the correct idle speed. The computer stores this new bypass valve position in its memory. Over time, this can become a fairly substantial adjustment, but the change occurs so gradually, you will never notice it happening.
Unfortunately, when the battery is disconnected, some late model vehicles will lose this learned idle position, which will cause the vehicle to stall.
You can try one or both of these procedures try to correct stalling:
Clean the deposits built up on the throttle body (Throttle Body Service) using aerosol brake cleaner and a shop towel. This will allow the default idle air bypass valve value to function correctly. The idle learn procedure will begin again as it did when the vehicle was new. Some basic repair knowledge may be necessary to complete this procedure.
You can also perform the following procedure to try to force the engine computer to quickly relearn the necessary bypass valve position when stalling occurs:
Warm the engine, but hold your foot on the throttle as necessary to keep the engine running.
With the transmission in Park, slowly release the throttle so that the engine will idle on its own. You may have to work at this a bit.
Let the engine idle on its own for about one minute.
Continue to let the engine idle and with your foot on the brake, place the transmission in Drive and let the engine idle for another minute.
Continue to let the engine idle with your foot on the brake and the transmission in Drive. Turn the A/C on and let the engine idle for another minute with the A/C compressor running.
Turn the ignition off and wait a minute.