Fitment notes: AGM battery required; located under hood on right side; start-stop system equipped
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Every control module on the 2021-2026 Mercedes-Benz GLS — 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.
Hybrid Control Unit / Battery Management System (HCU/BMS)3.0 hr R&Rsecurity gateway +2.0 hr▸ programming details
📍 Under rear cargo floor or rear seat area
🔧 Xentry Diagnostics + SCN online
⚠️ GLS 580 4MATIC (mild hybrid) only. VIN-locked, requires high-voltage system isolation and battery pack calibration. Dealer-only procedure with HV safety protocols.
Transmission Control Unit (TCU)2.5 hr R&Rsecurity gateway +1.0 hr▸ programming details
📍 Transmission housing or adjacent to transmission
🔧 Xentry Diagnostics + SCN online
⚠️ VIN-locked, requires SCN coding. Transmission fluid change often required during R&R.
Airmatic / Active Body Control Module (ABC/ADS)2.5 hr R&Rsecurity gateway +1.5 hr▸ programming details
📍 Front left engine bay or under vehicle near front axle
🔧 Xentry Diagnostics + SCN online
⚠️ VIN-locked. E-Active Body Control on 2021+ models. Requires ride height calibration, damper adaptation, and level sensor learning. System bleed may be required.
Electric Power Steering Control Unit (EPS)2.0 hr R&Rsecurity gateway +1.0 hr▸ programming details
📍 Steering column or rack housing
🔧 Xentry Diagnostics + SCN online
⚠️ VIN-locked, requires steering angle sensor calibration and end-stop learning.
Signal Acquisition and Actuation Module - Roof (SAM-Roof)2.0 hr R&Rsecurity gateway +1.0 hr▸ programming details
⚠️ VIN-locked. Requires precise radar alignment using factory alignment tool. ADAS calibration mandatory after replacement or collision. Enhanced range on 2021+ models.
⚠️ Separate modules for driver and passenger. Requires position calibration after replacement. Enhanced massage functions on 2021+ models.
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 GLS 4.0L Turbo V8 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.