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What is code p1639 how do you change it

(2001 Ford Expedition)
in Victorville, CA on December 21, 2011
how do you get into the diagnostic code
Displaying 2 answers & 0 comments
Popular Answer
on December 21, 2011
Flash Electrically Eraseable Programmable Read Only Memory - Flash EEPROM


Flash Electrically Eraseable Programmable Read Only Memory (EEPROM) is contained in an Integrated Circuit (IC) internal to the Powertrain Control Module (PCM) . The 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. The VID block must be programmed when replacing the PCM as under Programming the VID Block for a Replacement PCM. Failure to perform this procedure may generate fault code: P1639, VID Block not programmed or is corrupt. The VID block in an existing Powertrain Control Module (PCM) . can also be tailored to accommodate various hardware changes made to the vehicle since production. Failure to perform this procedure properly may generate fault code: P1635, Tire/Axle Ratio out of Acceptable Range. 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 versus manual shift on the fly. Only items applicable to vehicle hardware and supported by the VID block will be displayed on the scan tool.

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

Each of the procedures described below use the Worldwide Diagnostic System (WDS) . Reprogramming can be performed 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 diagnostic tool manufacturers users manual for details.

Programming the VID Block for a Replacement PCM
A new PCM will contain the latest strategy and calibration level for a particular vehicle. However, the VID block will be blank and will need programming. There are two procedures available. The first is an automatic data transfer from the old PCM to the new PCM and the second is manual data entry into the new PCM.

Automatic data transfer will be performed if the old PCM is capable of communicating. This is done by the use of a scan tool to retrieve data from the old PCM before removing it from the vehicle. The stored data can now be downloaded to the new PCM after it has been replaced.

Manual data entry must be performed if the old module is damaged and is incapable of communicating. Remove and replace the old PCM. You may be instructed to contact the "AS BUILT" data center for the information needed to manually update the VID block with the scan tool. Contact the center ONLY if the old PCM cannot be used or the data is corrupt. For Ford L-M technician's, contact your National Hotline for "AS Built" data. Non Ford technicians, use the Fed World website at "". Select Auto Service Information and search for "Calibrations" or "Vehicle Calibrations" then specify vehicle manufacturer, model name and model year as required.

Making Changes to the VID Block
A PCM which is programmed may require changes to be made to certain VID information to accommodate vehicle hardware. Refer to PCM/Module Reprogramming on the Scan Tool.

Making Changes to the PCM Calibration
At certain times, the entire EEPROM will need to be completely reprogrammed. This is due to changes made to the strategy or calibration after production or the need to reset the VID block because it has reached its limit. Refer to PCM/Module Reprogramming on the Scan Tool.

there is nothing you can do for this. it has to be done by a shop that can flash your pcm.

on December 22, 2011
Tests/Procedures: 1. Monitor the Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT) readings at idle and off of idle, with no load.

2. If the STFT readings are seen to be high at idle, nurse an alternative fuel supply, such as acetylene or propane, around the rear of the intake manifold to see if the STFT readings are affected, indicating the source of a vacuum leak.

3. Follow the line back from the Positive Crankcase Ventilation (PCV) valve to the rear of the engine, inspect for a collapsed or leaking line or fitting.

4. Code P1639 suggests that the PCM was replaced on this vehicle and not properly programmed for function in the vehicle. Program the PCM to the latest calibration available for the vehicle and recheck for the setting of the code. If P1639 is still setting, the PCM will need to be replaced.
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