Possible causes

– New PCM-Needs programming
– Incorrect VID configuration

Tech notes

After a new PCM has been installed, the Vehicle Identification (VID) block has to be program to the PCM.

There is a service bulletin for the P1639 code for the following models:
2002 Mercury Mountaineer
Mercury Factory Service Bulletin OBDII Code P1639

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1639 MERCURY Description

Vehicle ID block is not programed or is corrupt

MERCURY Technical Service Bulletins for P1639 code