Disconnecting A Car Battery Can Be Costly

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Disconnecting Your Car Battery Can Be Costly on a Ford or BMW

Disconnecting or replacing your battery can lead to erratic behavior in the performance, idle, and other related drive-ability issues. Ford did not incorporate the (PROM) Program Read Only Memory in its computer. Other manufactures have different procedures, so please read your owner’s manual or ask the auto repair technician here on our site and we will be glad to help you.

Ford’s Failure Mode Effects Management (FMEM) states in order for the computer to relearn its systems of inputs and outputs you must use this procedure for the vehicle’s computer to re-learn by using adaptive learning techniques.

Definition of FMEM:

Failure mode effects management (FMEM) is an alternate system strategy in the powertrain control module (PCM) designed to maintain vehicle operation if one or more sensor inputs fail. When a sensor input is perceived to be out-of-limits by the PCM, an alternative strategy is initiated. The PCM substitutes a fixed value and continues to monitor the incorrect sensor input. If the suspect sensor operates within limits, the PCM returns to the normal engine running strategy.

FMEM Procedure:

  • Start the engine allow it to warm up to normal operating temperature.
  •  Raise RPM to 2000 and hold it for two minutes. (needed for to heat up the oxygen (02) sensors).
  • Then if you have a/c turn it on and allow to run for 5 minutes.
  • Continue on with depressing the brake pedal once and let go – for those who have cruise control (this is for the BOO Switch- Brake On/ Brake Off Switch).
  • In addition, turn the steering wheel half way one direction to the other direction and leave it there.
  • Finally, drive the vehicle for 5 miles.

Customers have complained about rough idle, car cuts out when they make a turn or turn on a/c and the cars idle is too low and cuts out. For those of you who are computer literate when you format your hard drive the drive is wiped out clean of everything, then you have to install an operating system before the computer will work. The car’s computer is kept alive by the battery and when power is interrupted so is its memory. For some makes and models you will have to teach the computer what its inputs and outputs are, for instance, does the car have A/C, ABS, or Cruise Control? Battery Maintainer will save you headaches down the line in avoiding  having  to spend money on re-programming the computer or Navigation equipment, and too, spending money to get your radio working again because you cannot remember the Radio Code.

To help you save radio presets, clock settings, and computer memory and especially saving you money on having to pay for a Radio Code. To get your battery saver tool today – click this link Tools For Sale Cheap Auto Repair Help US

I have seen to many car and truck forums, auto groups, and crowed sourced web sites, which the expert tells the customer to disconnect the battery to clear codes to correct the problem. Watch out!! Some cars will be damaged and/or in need of reprogramming.

BMW Corp. States:

Let us take, for example, a 2001 BMW 325I Sedan (E46). The MK3 Navigation computer powers down in approximately 60 seconds after the ignition has been turned OFF (red LED on the computer goes OFF). If the power supply to the MK3 unit is interrupted (by removing disconnecting the computer from the vehicle, or by disconnecting the vehicle’s battery) in the time period of 55 to 57 seconds after the ignition has been turned OFF, the power-down procedure (“erase and save data in Non Volatile RAM“) can be corrupted.

This will result in a total failure of the MK3 computer (red LED off, CD eject function inoperative, board monitor screen permanently blank, and no sound from the audio system). In such a case, the navigation computer has to be replaced.

On vehicles with MK3 navigation system, prior to disconnecting the battery or removing (disconnecting) the Navigation computer, make sure the MK3 Navigator’s computer is in the power-down mode (red LED on the unit is OFF) by using the magnetic pen,

Battery Saver Tool at www.autorepairhelp.us

WARRANTY INFORMATION: Damaged MK3 Nay computers caused by not following the required power-down procedure are not considered defective and are not warranty covered.

Automotive Tip:


Above are two examples in taking the time to follow all procedures before disconnecting your automotive battery. Radio codes, and all the settings will be lost due to battery disconnect. Some automotive makes and models you can use a Battery Saver Tool. Plugs right in the Cigarette lighter to help you keep all engine codes and feature settings intact, so you will not have to reprogram the radio and all its’ settings. Including covenant settings, such as memory power seats, clock, radio stations and not having to pay to get a Radio Code to get your radio working again.

Domestic and Import car, truck, and van owners:
Please consult your vehicle Owner’s Manual before you disconnect your car’s battery to see if your car has a disconnect procedure.

Ask a Technician Now to see if your car’s battery can be safely disconnected.

To maintain voltage continuity to your engine computer, clock, and radio memory when your vehicle battery is disconnected, be sure that you’re using battery maintainers from Auto Repair Help.US. These computer memory keepers use a 9 V battery, not included, to plug into your vehicle’s cigarette lighter outlet to retain radio presets, ECM codes, and learned procedures for up to four hours. Don’t disconnect your battery until you have first hooked up with these Performance Tool battery maintainers!

Note: GM does not have this problem because GM incorporates the PROM in its computers. The battery saver will help GM owners save their radio presets, clock, and keep from having to spend money on Radio Codes.

Thank you, and Happy Motoring, Lee Davidian, Sr.

Disconnecting A Car Battery Can Be Costly

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