Fitment notes: AGM battery required for start-stop system; located in engine bay; high-performance AMG variant requires higher CCA rating
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Every control module on the 2020-2026 Mercedes-Benz A45 AMG W177 — 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
📍 Transmission housing, driver side
🔧 Xentry Diagnostics + SCN online
⚠️ AMG Speedshift DCT 8-speed. Requires transmission adaptation procedure after coding. Fluid change recommended during R&R.
4MATIC Control Unit (4M)2.0 hr R&Rsecurity gateway +0.8 hr▸ programming details
📍 Transmission tunnel, center under vehicle
🔧 Xentry Diagnostics + SCN online
⚠️ AMG Performance 4MATIC+ with drift mode. Requires drivetrain adaptation and road test after coding.
MBUX Head Unit (HU/MBUX)2.0 hr R&Rdealer / factory tool +0.5 hr▸ programming details
📍 Center dashboard, integrated with display
🔧 Xentry Diagnostics
⚠️ 10.25-inch touchscreen. Navigation and user profile data transfer recommended. May require software update after replacement.
Electric Power Steering Control Unit (EPS)1.8 hr R&Rsecurity gateway +0.8 hr▸ programming details
📍 Steering column, below instrument panel
🔧 Xentry Diagnostics + SCN online
⚠️ AMG Performance Steering. Steering angle sensor calibration and road test required after coding.
Climate Control Unit (CCU)1.5 hr R&Rdealer / factory tool +0.3 hr▸ programming details
📍 Behind center dashboard, above center console
🔧 Xentry Diagnostics
⚠️ Dual-zone automatic climate. Actuator calibration required after replacement.
Electronic Stability Program Control Unit (ESP/ABS)1.5 hr R&Rsecurity gateway +0.8 hr▸ programming details
📍 Engine bay, left front corner near brake master cylinder
🔧 Xentry Diagnostics + SCN online
⚠️ Integrated hydraulic unit. Brake bleeding required after replacement. Steering angle sensor calibration mandatory.
Rear Signal Acquisition and Actuation Module (SAM-R)1.5 hr R&Rsecurity gateway +1.0 hr▸ programming details
⚠️ 12V auxiliary battery management for start-stop system. Battery registration 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 2025 Mercedes-Benz A45 AMG W177 2.0L I4 Turbo M139 and can vary by trim.
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Lexus & Toyota Mechanic · 20+ years.