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What all is reset when the battery is disconnected?
I'm tired of battery drain and am thinking of throwing a battery disconnect in for when I'm away from the car for a long time.
Will it affect the engine tune to have the battery disconnected for weeks at a time?
If you have a custom tune, it will NOT be affected by having the battery disconnected for long periods of time. What is affected is the fuel trims that are learned by the computer when you drive the car. These are fine adjustments that the computer can make based on driving conditions. These relearn by just driving the car for 50 to 75 miles. Worst case the car may not idle as smoothly as you might like until the relearn is complete.
If you have the Theft Lok set on your radio, you will need to unlock it when you reconnect the battery. Any radio presets may also be gone.
A better choice would be to get yourself a battery tender style charger and leave it connected when you cannot drive the car for long periods of time.
NO it will NOT effect the tune or hurt the BCM/PCM or any other module. In FACT,,, the OWNERS MANUAL recommends "Disconnecting the Battery" for long periods of stowage.
When you disconnect the battery you will resert the learned LTFT data, all the FOB Memory data and fuel efficiency data will all reset & default to the factory settings. You will also have to re-sync your FOBS. You also cause the PCM to set all of the EMISSIONS NOT READY flage and if you have to get an emissions check, you will have to go thru a number of drive cycles before the FLAGS set to ready.
The LTFT Data will regenerate and learn after a short drive. You just have to reprogram all the seat/dash memory settings manually.
Why not just FIX the problems that are causing your battery to drain??? Its not all that difficult. Insert an AMP meter in series with the NEG Battery Cable and read the DC Amperage that the BCM and PCM draw after the system goes into sleep mode. It should be very close to 0.020 AMPS or 20 milliamps. At that minimum current draw, the car should be able to sit idle for inexcess of 30 days (seen it start without any issues after 2 months of storrage if the battery is in good condition and fully charged!)
Last edited by Bill Curlee; 04-19-2011 at 01:33 PM.
They make a gaget that plugs into your cig lighter port with a 9v batery in it used for disconecting bateries and saving mem functions, radio presets, ect. not sure how long they last on a 9v batery tho. they sell them at walmart near the car bateries.