B1001

B1001 is a VIN mismatch fault — one or more modules on the vehicle have a VIN programmed into them that does not match the VIN reported by the master controller (usually the BCM or PCM). This is almost never a hardware failure; it is a programming/configuration problem, and it sets after module replacement, used-module installation from a salvage yard, theft-recovery reflash situations, or occasionally after a botched dealer reprogramming attempt. Cheapest first: read the VIN from every module on the bus with a capable scan tool (this is a free check if you already own one) and identify which module disagrees with the rest — the offending module is almost always one that has been recently replaced. The fix is a VIN write/program operation, which on most platforms requires a dealer-level scan tool (Tech 2/MDI/GDS2 for GM, IDS for Ford, wiTECH for FCA) or a competent locksmith/programmer with the right software. Some modules are write-once and cannot be re-VINed without a factory tool — these are commonly seen on theft-deterrent and key-immobilizer modules. The expensive misdiagnosis: replacing the module a second time, thinking it failed, when the actual fault is just that nobody programmed the VIN into the first replacement; this doubles the parts cost and still does not fix the problem.

Vehicle-specific patterns: 2004-2013 GM trucks/SUVs — VIN write required on any replacement BCM, ECM, or instrument cluster; Tech 2 or AllData/Mitchell programming required. 2005-2010 Ford F-150 — used PCM from salvage will set B1001 until IDS reflash. 2007-2012 Chrysler/Dodge/Jeep — TIPM and SKREEM require VIN match; wiTECH dealer tool needed. 2008-2014 Hyundai/Kia — Smartra immobilizer module is VIN-locked, salvage-yard installs almost always fail. Estimated repair: $75 to $600.