Electric Power Steering Motor

This procedure covers the removal and replacement of the electric power steering motor on the 2007-2013 Mercedes-Benz S65 AMG with the M275 6.0L V12 BiTurbo engine.

Warnings

Tools required

Parts

• Electric power steering motor assembly × 1 — A0054668801 or equivalent OEM
• Power steering line O-rings × 4 — Use OEM specification
• Steering motor mounting bolts × 3 — Use OEM specification if corroded

Fluids

• Pentosin CHF 11S — 1 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Turn steering wheel to center position and lock ignition
3. Disconnect negative battery terminal and wait 10 minutes for system capacitor discharge
4. Raise front of vehicle and secure on jack stands at manufacturer-specified lift points
5. Remove front wheels
6. Remove lower engine splash shield and front underbody panels for access
7. Place drain pan under power steering reservoir and use turkey baster to remove fluid from reservoir

Procedure

1. 1

   Access steering motor compartment
   Remove the front driver-side wheel well liner by removing plastic rivets and screws. Pull liner back to expose steering rack area. Remove acoustic insulation panels from firewall area above steering rack to provide working clearance.
2. 2

   Disconnect electrical connectors
   Locate the power steering motor on the driver's side of the steering rack. Press the release tab and disconnect the main power connector from the steering motor. Disconnect the secondary sensor connector. Secure connectors away from work area to prevent contamination with steering fluid.
   ⚠Do not pull on wires. Use proper connector release tabs to avoid damaging terminals.
3. 3

   Remove motor protective cover
   Remove the protective cover from the steering motor assembly by removing the cover screws. Set cover aside in clean area. Inspect cover gasket and replace if damaged.
4. 4

   Disconnect power steering lines
   Position drain pan directly beneath power steering motor connections. Using proper flare nut wrench, carefully loosen and remove the high-pressure and return line fittings from the steering motor. Allow fluid to drain completely. Cap open ports immediately to prevent contamination.
   ⚠Residual pressure may remain in lines. Loosen fittings slowly and be prepared for fluid discharge.
5. 5

   Remove steering motor mounting bolts
   Support the weight of the steering motor with one hand or suitable support. Remove the three mounting bolts securing the steering motor to the steering rack housing. Note bolt positions as they may be different lengths.
6. 6

   Extract steering motor
   Carefully pull the steering motor assembly away from the steering rack. The motor shaft will disengage from the rack pinion. Tilt and rotate as needed to clear surrounding components. Remove motor from vehicle through wheel well opening.
   ⚠Do not allow motor to hang by electrical connectors. Support full weight during removal.
7. 7

   Prepare new steering motor
   Unpack new steering motor and verify part number matches application. Remove shipping caps from fluid ports. Install new O-rings on all fluid connection points, lubricating lightly with clean CHF 11S fluid. Inspect motor mounting surface on steering rack and clean with brake cleaner if necessary.
8. 8

   Install new steering motor
   Position new steering motor to steering rack, aligning the motor shaft with the rack pinion gear. Ensure proper engagement by rotating motor slightly while applying gentle pressure. Motor should seat flush against mounting surface. Install mounting bolts finger-tight initially.
9. 9

   Torque mounting bolts
   Torque the three mounting bolts in a star pattern to specification. Verify motor is properly seated with no gaps between motor housing and rack.
10. 10

    Reconnect power steering lines
    Remove caps from fluid ports. Thread power steering line fittings into motor ports by hand to ensure proper thread engagement. Torque fittings to specification using proper flare nut wrench. Verify O-rings remain properly seated.
11. 11

    Reinstall protective cover
    Position protective cover over steering motor. Install and torque cover screws to specification in cross pattern.
12. 12

    Reconnect electrical connectors
    Reconnect both electrical connectors to steering motor, ensuring positive click engagement. Verify connector seals are properly seated to maintain weatherproof integrity.
13. 13

    Refill and bleed power steering system
    Fill power steering reservoir with Pentosin CHF 11S to MAX mark. Reconnect battery. Turn ignition to position 2 (do not start engine). Turn steering wheel lock-to-lock 10 times slowly. Check fluid level and top off as needed. Start engine and repeat lock-to-lock steering while checking for leaks at motor connections. Add fluid to maintain proper level.
    ⚠Do not hold steering at full lock for more than 2 seconds to avoid damaging pump.
14. 14

    Calibrate steering angle sensor
    Using Mercedes-Benz Star Diagnostic System, perform steering angle sensor calibration procedure. Navigate to steering control module and execute 'Steering Angle Sensor Alignment' function. Follow on-screen prompts to center steering and complete calibration. Clear all fault codes from steering and ESP systems.

Reassembly

1. Reinstall all underbody panels and acoustic insulation in reverse order of removal
2. Reinstall wheel well liner ensuring all fasteners are properly secured
3. Install front wheels and torque lug nuts to specification in star pattern
4. Lower vehicle to ground and perform final torque check on wheel lug nuts
5. Top off power steering fluid reservoir to MAX mark after test drive

Verification

• Start engine and verify no warning lights related to steering, ESP, or ABS systems
• With engine running, turn steering wheel lock-to-lock and verify smooth operation with no binding or unusual noises
• Inspect all power steering line connections at motor for leaks with engine running and steering in motion
• Perform test drive at low speed in safe area, verifying proper steering assist and no warning lights
• Re-check power steering fluid level after test drive and top off if necessary
• Verify steering angle sensor calibration by driving straight and confirming steering wheel is centered with no ESP light
• Use diagnostic scan tool to verify no active or pending fault codes in steering or suspension systems

Related trouble codes on this vehicle

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