Why it happens
The engine computer, the key module and sometimes the cluster share a secret. Swap one with a used part and the secret no longer matches.
Which modules matter
- Engine computer (ECU, ECM, DME)
- Instrument cluster (many VW, Audi, older GM)
- Ignition or key module (BMW CAS, Mercedes EIS)
- Body module (newer cars)
How it's fixed
We read the data from the original part or the car, then write it to the replacement, or add your keys to the new module. Some jobs are on site, some need bench work.
Before you buy a used module
Ask whether it can be matched to your car. Some modules are one-time-programmable. Text us the part and car first.
Written by the Keyhub Locksmith team, a mobile car locksmith in Marietta, GA. Updated October 23, 2026.