Fitment notes: Location: Trunk / rear compartment area, mounted separately from the main 12V starter battery (Mercedes R232 packages the auxiliary AGM in a rear side compartment; engine-bay/firewall placement is used on some other models but the rear location is the better-supported description here) · Purpose: Onboard electrical system voltage support \u2014 stabilizes supply voltage during high electrical loads and during start-stop engine restarts, and acts as a backup supply for safety-critical electronics
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Every control module on the 2021-2026 Mercedes-Benz SL55 AMG — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
Transmission Control Unit (TCU)2.5 hr R&Rsecurity gateway +1.0 hr▸ programming details
⚠️ Controlled by SAM-R but separate module. Adaptation required after replacement.
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2026 Mercedes-Benz SL55 AMG 4.0L V8 BiTurbo M177 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years.