Every control module on the 2025 Mercedes-Benz GLC300 X254 — 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.
Electric Power Steering Control Unit (EPS) 2.8 hr R&R security gateway +1.0 hr ▸ programming details
📍 Steering column, integrated with steering gear assembly
🔧 Xentry Diagnostics + SCN online
⚠️ Requires steering angle sensor calibration and road test after coding. Wheel alignment recommended.
Transmission Control Unit (TCU) 2.5 hr R&R security gateway +1.0 hr ▸ programming details
📍 Transmission housing, driver side near valve body
🔧 Xentry Diagnostics + SCN online
⚠️ 9G-TRONIC transmission. Requires transmission fluid change during R&R. VIN-locked SCN coding mandatory.
MBUX Head Unit (HU/MBUX) 2.0 hr R&R security gateway +1.5 hr ▸ programming details
📍 Dashboard center, integrated with center display
🔧 Xentry Diagnostics + SCN online
⚠️ MBUX 2.0 system. Requires online account synchronization and feature activation. Navigation and user profile transfer needed.
4MATIC Control Unit (4M) 2.0 hr R&R security gateway +0.8 hr ▸ programming details
📍 Transfer case housing, center of vehicle under transmission
🔧 Xentry Diagnostics + SCN online
⚠️ AWD system control. Requires drivetrain adaptation and road test after coding. Present on 4MATIC models only.
Signal Acquisition and Actuation Module - Rear (SAM-R) 1.8 hr R&R security gateway +1.0 hr ▸ programming details
📍 Rear cargo area, left side panel behind trim
🔧 Xentry Diagnostics + SCN online
⚠️ Controls rear lighting, fuel pump relay, trailer functions. VIN-locked.
Central Gateway Module (CGW) 1.8 hr R&R security gateway +2.0 hr ▸ programming details
📍 Dashboard left side, near SAM-F location or integrated
🔧 Xentry Diagnostics + SCN online
⚠️ Security gateway. Replacement requires extensive network reconfiguration and all module re-authentication. Dealer-only procedure.
Climate Control Unit (CCU) 1.5 hr R&R dealer / factory tool +0.5 hr ▸ programming details
📍 Dashboard center, behind HVAC control panel
🔧 Xentry Diagnostics
⚠️ Requires HVAC actuator calibration after replacement. Some aftermarket tools can perform basic coding.
Electronic Ignition Switch (EIS) 1.5 hr R&R security gateway +1.5 hr ▸ programming details
📍 Steering column, ignition switch area
🔧 Xentry Diagnostics + SCN online
⚠️ Security-critical. All keys must be reprogrammed. Requires online authorization and component protection reset.
Occupant Classification System (OCS) 1.5 hr R&R security gateway +0.8 hr ▸ programming details
📍 Passenger seat, integrated in seat cushion
🔧 Xentry Diagnostics + SCN online
⚠️ Passenger airbag suppression system. Safety-critical. Requires calibration with special weight set after replacement.
Camera Control Unit / Surround View (CCU) 1.5 hr R&R security gateway +1.0 hr ▸ programming details
📍 Dashboard center, behind MBUX head unit or integrated
🔧 Xentry Diagnostics + SCN online
⚠️ 360-degree camera system. Requires camera calibration and alignment procedure. Multiple cameras (front, rear, side mirrors).
Airmatic / Adaptive Damping System Control Unit (ADS/Airmatic) 1.5 hr R&R security gateway +1.0 hr ▸ programming details
📍 Front left wheel well area or under front passenger seat
🔧 Xentry Diagnostics + SCN online
⚠️ Optional air suspension system. Requires ride height calibration and damper adaptation. VIN-locked on X254.
Door Control Module (DCM) 1.2 hr R&R dealer / factory tool +0.4 hr ▸ programming details
📍 Inside each door, behind door panel (4 total)
🔧 Xentry Diagnostics
⚠️ Controls windows, mirrors, locks per door. Requires window initialization and mirror calibration after coding.
Motor Electronics / Engine Control Unit (ME/ECU) 1.2 hr R&R security gateway +1.0 hr ▸ programming details
📍 Engine compartment, left side firewall near brake booster
🔧 Xentry Diagnostics + SCN online
⚠️ VIN-locked, requires online SCN authorization from Mercedes servers. Must perform component protection reset.
Radar Sensor / DISTRONIC Control Unit (RSU) 1.2 hr R&R security gateway +1.5 hr ▸ programming details
📍 Front bumper center, behind Mercedes star emblem
🔧 Xentry Diagnostics + SCN online + radar alignment tool
⚠️ Adaptive cruise control and collision prevention. Requires precise radar alignment with special target tool. Additional rear radar may be present.
Telematics Communication Module (TCM) 1.2 hr R&R security gateway +1.0 hr ▸ programming details
📍 Rear cargo area, right side panel or under rear seat
🔧 Xentry Diagnostics + SCN online
⚠️ 5G/LTE connectivity. Requires Mercedes me account reactivation and SIM provisioning after replacement.
Electronic Stability Program Control Unit (ESP/ABS) 1.0 hr R&R security gateway +0.8 hr ▸ programming details
📍 Engine compartment, left front near wheel well
🔧 Xentry Diagnostics + SCN online
⚠️ Integrated hydraulic unit. Requires brake bleeding after replacement. SCN coding and steering angle sensor calibration mandatory.
Instrument Cluster (IC) 1.0 hr R&R security gateway +0.8 hr ▸ programming details
📍 Dashboard, behind steering wheel
🔧 Xentry Diagnostics + SCN online
⚠️ VIN-locked. Mileage programming requires dealer authorization. Digital cluster with 12.3-inch display.
Intelligent Light System Control Unit (ILS) 1.0 hr R&R dealer / factory tool +0.5 hr ▸ programming details
📍 Engine compartment, behind headlight assemblies (left and right)
🔧 Xentry Diagnostics
⚠️ LED headlights with adaptive function. Requires headlight aim calibration after replacement.
Tailgate Control Module (TGM) 1.0 hr R&R dealer / factory tool +0.4 hr ▸ programming details
📍 Tailgate, behind interior trim panel
🔧 Xentry Diagnostics
⚠️ Power liftgate with hands-free function. Requires height calibration and pinch protection learning after replacement.
Parktronic Control Unit (PTS) 1.0 hr R&R dealer / factory tool +0.5 hr ▸ programming details
📍 Rear cargo area, center behind trim or near spare tire well
🔧 Xentry Diagnostics
⚠️ Parking sensors front and rear. Requires sensor calibration after replacement.
Restraint Systems Control Unit (SRS) 0.8 hr R&R security gateway +0.8 hr ▸ programming details
📍 Center console, under front seats mounting area
🔧 Xentry Diagnostics + SCN online
⚠️ Safety-critical. VIN-locked. Must verify all crash sensor and occupant detection calibrations after coding.
Fuel Pump Control Module (FPCM) 0.8 hr R&R dealer / factory tool +0.3 hr ▸ programming details
📍 Rear cargo area, left side panel near fuel tank
🔧 Xentry Diagnostics
⚠️ Controls fuel pump relay and pressure regulation. Basic coding usually sufficient.
Seat Control Module (SCM) 0.8 hr R&R aftermarket tool +0.3 hr ▸ programming details
📍 Under front seats (driver and passenger)
🔧 Xentry or Autel MaxiSys
⚠️ Controls power seat, heating, ventilation, massage. Usually one per front seat. Basic adaptation possible with aftermarket tools.
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?
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