Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Transmission Control Module Flashing (27.19/121)
Reference number: 27.19/121
TRANSMISSION CONTROL MODULE FLASHING
TECHNICAL SERVICE BULLETIN
| MERCEDES-BENZ: | MY-All, Models All |
| GROUP: | 27 - Automatic Transmission |
SUBJECT
MY-All, Models All
Transmission Control Module Flashing
Do not flash the transmission control module, unless specifically instructed to do so in a technical document, such as a LI, Service Bulletin, Campaign, or Diagnostic Tree; or the SDS Diagnostic System indicates to do so.
Failure to adhere to this policy will result in rejected warranty claim or a debit.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.