Fitment notes: Located in trunk; AGM required for start-stop system and electrical demands
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Every control module on the 2021-2026 Mercedes-Benz S-Class — 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)3.5 hr R&Rsecurity gateway +1.0 hr▸ programming details
📍 Transmission bell housing or valve body (9G-TRONIC)
🔧 Xentry Diagnostics + SCN online
⚠️ Requires transmission oil change, adaptation drive cycle, and SCN coding. Often integrated with valve body.
Airmatic / E-Active Body Control Module (E-ABC)2.5 hr R&Rsecurity gateway +1.5 hr▸ programming details
📍 Front of vehicle, near radiator support
🔧 Xentry Diagnostics + SCN online
⚠️ 48V electro-hydraulic active suspension. Requires ride height calibration, road test, and extensive adaptation. Complex system.
Climate Control Unit (CCU)2.5 hr R&Rdealer / factory tool +0.5 hr▸ programming details
📍 Behind dashboard center stack
🔧 Xentry Diagnostics
⚠️ Requires HVAC system calibration and blend door relearn. Multi-zone systems with rear executive controls.
Head Unit / MBUX (HU/MBUX)2.5 hr R&Rsecurity gateway +1.5 hr▸ programming details
📍 Dashboard center stack (12.8-inch OLED portrait display)
🔧 Xentry Diagnostics + SCN online
⚠️ Second-generation MBUX with augmented reality navigation. Requires extensive coding and user profile transfer. Rear entertainment system separate.
Hybrid Control Unit / Battery Management System (HCU/BMS)2.0 hr R&Rsecurity gateway +1.5 hr▸ programming details
📍 Under vehicle or trunk area (48V system)
🔧 Xentry Diagnostics + SCN online
⚠️ 48V mild hybrid system standard on most models. Requires high-voltage safety procedures and extensive calibration. Plug-in hybrid models have additional high-voltage components.
Electric Power Steering Control Unit (EPS)2.0 hr R&Rsecurity gateway +1.0 hr▸ programming details
📍 Steering column or rack assembly
🔧 Xentry Diagnostics + SCN online
⚠️ Requires steering angle sensor calibration and road test. Rear-axle steering models have additional module.
Roof Signal Acquisition and Actuation Module (SAM-Roof)1.8 hr R&Rsecurity gateway +1.0 hr▸ programming details
📍 Overhead console or A-pillar area
🔧 Xentry Diagnostics + SCN online
⚠️ Controls panoramic roof, interior lighting, rain sensor. Not present on all trim levels.
📍 Under each seat (front and rear on long wheelbase)
🔧 Xentry Diagnostics
⚠️ Controls seat adjustment, heating, ventilation, massage, active bolsters. Rear executive seats have extensive functionality.
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 S-Class 3.0L Turbo I6 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Mechanic · 20+ years.