Flash Electrically Erasable Programmable Read Only Memory (EEPROM): Description

Flash EEPROM is contained in an integrated circuit internal to the powertrain control module (PCM) and the fuel injection control module (FICM). The flash EEPROM contains the vehicle strategy, including calibration information specific to the vehicle, and is capable of being reprogrammed or reflashed repeatedly.

As part of the calibration there is an area referred to as the vehicle identification (VID) block in the PCM. The VID block must be programmed when installing a new PCM as described under Programming the VID Block for a New PCM. Not carrying out this procedure may generate DTCs: P1635, P1639, VID Block not programmed or is corrupt. The VID block in an existing PCM can also be tailored to accommodate various hardware/parameter changes made to the vehicle since production. Not carrying out this procedure correctly may generate DTC P1635, Tire/Axle Ratio out of Acceptable Range, is one of the main causes for DTC P1639. This is described under Making Changes to the VID Block, and also under Making Changes to the PCM Calibration. The VID block contains many items used by the strategy for a variety of functions. Some of these items include the VIN number, octane adjust, fuel octane, fuel type, vehicle speed limit, tire size, axle ratio, the presence of speed control, and four wheel drive electronic shift-on-the-fly (ESOF) versus manual shift-on-the-fly (MSOF). Only items applicable to the vehicle hardware and supported by the VID block are displayed on the scan tool.

When changing items in the VID block, the strategy places range limits on certain items such as tire and axle ratio. The VID block is also limited to the number of times it can be reconfigured. When this limit is reached, the scan tool displays a message indicating the need to flash the PCM again to reset the VID block.

Each of the procedures described below use the scan tool. Reprogramming can be carried out by a local Ford dealer for any non-Ford facility. There are other enhanced scan tools that may have reprogramming capabilities available. Refer to the manufacturer's article for details.