Battery — disconnection and reconnection

Warning: On models with OnStar, make absolutely sure the ignition key is in the Off position and Retained Accessory Power (RAP) has been depleted before disconnecting the cable from the negative battery terminal. Also, never remove the OnStar fuse with the ignition key in any position other than off. If these precautions are not taken, the OnStar system’s backup battery will be activated, and remain activated, until it goes dead. If this happens, the OnStar system will not function as it should in the event that the main vehicle battery power is cut off (as might happen during a collision).

Note: To disconnect the battery for service procedures requiring power to be cut from the vehicle, first open the driver’s door to disable Retained Accessory Power (RAP), then loosen the cable end bolt and disconnect the cable from the negative battery terminal. Isolate the cable end to prevent it from coming into accidental contact with the battery terminal.

1. The battery is located in the right side of the engine compartment on all vehicles covered by this manual. To disconnect the battery for service procedures that require battery disconnection, simply disconnect the cable from the negative battery terminal (see Battery and battery tray — removal and installation). Make sure that you isolate the cable to prevent it from coming into contact with the battery negative terminal.

Caution: If both battery cables are to be disconnected, to prevent damage to any electrical components, always disconnect the negative battery cable first, then the positive battery cable second. When reconnecting the battery cables, always connect the positive battery cable first, then the negative battery cable second.

2. Some vehicle systems (radio, alarm system, power door locks, etc.) require battery power all the time, either to enable their operation or to maintain control unit memory (Powertrain Control Module, automatic transaxle control module, etc.), which would be lost if the battery were to be disconnected. So, before you disconnect the battery, note the following points:

a) Before connecting or disconnecting the cable from the negative battery terminal, make sure that you turn the ignition key and the lighting switch to their OFF positions. Failure to do so could damage semiconductor components.

b) On a vehicle with power door locks, it is a wise precaution to remove the key from the ignition and to keep it with you, so that it does not get locked inside if the power door locks should engage accidentally when the battery is reconnected!

c) After the battery has been disconnected, then reconnected (or a new battery has been installed) on vehicles with an automatic transaxle, the Transaxle Control Module (TCM) will need some time to relearn its adaptive strategy. As a result, shifting might feel firmer than usual. This is a normal condition and will not adversely affect the operation or service life of the transaxle. Eventually, the TCM will complete its adaptive learning process and the shift feel of the transaxle will return to normal.

d) The engine management system’s PCM has some learning capabilities that allow it to adapt or make corrections in response to minor variations in the fuel system in order to optimize drivability and idle characteristics. However, the PCM might lose some or all of this information when the battery is disconnected. The PCM must go through a relearning process before it can regain its former drivability and performance characteristics. Until it relearns this lost data, you might notice a difference in drivability, idle and/or (if you have an automatic) shift «feel.» To facilitate this relearning process, refer to «Enabling the PCM to relearn» below.

Memory savers

3. Devices known as memory savers (typically, small 9-volt batteries) can be used to avoid some of the above problems. A memory saver is usually plugged into the cigarette lighter, and then you can disconnect the vehicle battery from the electrical system. The memory saver will deliver sufficient current to maintain security alarm codes and — maybe, but don’t count on it! — PCM memory. It will also run unswitched (always on) circuits such as the clock and radio memory, while isolating the car battery in the event that a short circuit occurs while the vehicle is being serviced.

Warning: If you’re going to work around any airbag system components, disconnect the battery and do not use a memory saver. If you do, the airbag could accidentally deploy and cause personal injury.

Caution: Because memory savers deliver current to operate unswitched circuits when the battery is disconnected, make sure that the circuit that you’re going to service is actually open before working on it!

Enabling the PCM to relearn

4. After the battery has been reconnected, perform the following procedure in order to facilitate PCM relearning:

5. Start the engine and allow it to warm up to its normal operating temperature.

6. Drive the vehicle at part-throttle, under moderate acceleration and idle conditions, until normal performance returns.

7. Park the vehicle and apply the parking brake with the engine running.

8. Depress the brake pedal and put the shift lever in Drive.

9. Allow the engine to idle for about two minutes, or until the idle stabilizes. Make sure that the engine is at its normal operating temperature.

Resetting power windows, sunroof, and Electric Power Steering (EPS)

10. Power windows: Sit in the vehicle with all of the doors closed. Operate each window (one at a time) to the fully open position, then raise the window until it is closed and hold the switch in the UP position for five seconds.

11. Sunroof: Open the sunroof completely, then close it completely.

12. Electric Power Steering (EPS): Sit in the driver’s seat and start the engine. Turn the steering wheel completely counterclockwise, then completely clockwise, then back to center.

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