Occasionally you may read a vehicle only to be greeted with a checksum warning. The warning says you may have a permanent DTC or the car may not be drivable. In 90% of scenarios, checksum errors are harmless.

Harmless causes:

• You have an early BA with a blank VID block from the factory.
• Someone used Ford IDS improperly and wiped the VID block.
• You have a vehicle that was tuned with an early CAPA flash box or other third-party software which has no ability to update checksums.
• You used recovery mode on a third-party hand controller.
• PCMTEC Editor was closed improperly or crashed.

In these cases you can simply save the file and re-open it, PCMTEC Editor will recalculate and update the checksums. You can then flash the file in and the car will run and function exactly as it did previously. If the file does not open utilize a backup from the documents/PCMTEC/1.xx/Backups folder or re-read the vehicle.

Causes you should worry about:

• The vehicle was tuned with a handheld flash tuner which had incorrectly mapped tables.
• You had a corrupted read due to low voltage or a faulty J2534 dongle.
• Your PCM flash memory is corrupted.
• Your PC has bad RAM which has corrupted the file in memory.

In the case of a flash tuner causing the error you will see errors in the log such as "non-sequential table" or  "binary validation error". If you click on these errors and the table has strange numbers/dimensions this usually is due to an incorrectly mapped table in another product. In these cases, you will need to make a new stock file and copy the changes over.

In the cases above you can try reading the file from the PCM again and seeing if the checksum error persists.  If the checksum error persists and the car does not start, you most likely have a faulty PCM or a faulty J2534 cable.

If the vehicle does start and run then you most likely have a faulty J2534 cable. In this case, do not attempt to flash the vehicle until you have a second cable to test with.