engine

Crankshaft Position Sensor

for 2012 Mercedes-Benz S65 AMG 6.0L V12 BiTurbo M275 · RWD

Editorial review:Chris Hackleman — Master Technician · 20+ years

Difficulty

Moderate

Time

1.4 h

Tools

Steps

✓Expert-verified. Personally reviewed and approved by OLP's master technicians (Chris Hackleman — 20+ years each). Always follow the vehicle's factory service information and torque specs.

Replace the crankshaft position sensor on the M275 V12 BiTurbo engine to restore proper ignition timing and engine performance. This sensor is mounted on the crankcase and requires access from underneath the vehicle.

Warnings

⚠Allow engine to cool completely before starting work. The crankshaft position sensor is located near exhaust components that retain heat.

ℹ️The M275 engine uses two crankshaft position sensors (Hall effect type). This procedure covers the primary sensor on the crankcase. Verify which sensor requires replacement before ordering parts.

⚠Failure to properly disconnect the battery can result in fault codes being stored or module damage during sensor replacement.

Tools required

10mm socket and ratchetEssential

8mm socketEssential

Vehicle lift or jack standsEssential

Torque wrench (10-50 Nm range)Essential

Electrical contact cleaner

Small flathead screwdriver

Trim panel removal tools

Flashlight or work lightEssential

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Parts

Crankshaft position sensor × 1 — A0031539728 or equivalent OEM
Sensor O-ring seal × 1 — Usually included with sensor

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Preparation

Park vehicle on level surface and engage parking brake
Allow engine to cool for at least 1 hour
Open hood and locate battery in engine compartment (right side)
Disconnect negative battery terminal and wait 5 minutes for system discharge
Raise vehicle securely on lift or jack stands to access underside
Remove engine undercover panels using 8mm and 10mm fasteners

Procedure

1
Locate crankshaft position sensor
From underneath the vehicle, identify the crankshaft position sensor mounted on the lower passenger side of the engine block, approximately level with the oil pan. The sensor is a cylindrical component with a single electrical connector facing rearward. On the M275 engine, it is positioned between the transmission bellhousing and the front subframe.
2
Remove sensor electrical connector
Locate the electrical connector on the sensor body. Press the locking tab on the connector and pull straight back to disconnect. If the connector is difficult to access, trace the wiring harness back approximately 6 inches where it may be easier to disconnect. Note the routing of the wire harness for reinstallation.
3
Remove wire harness bracket
The sensor wire harness is secured by a plastic bracket or clip attached to the engine block. Using a small flathead screwdriver or trim tool, carefully release the harness bracket. This prevents wire tension from interfering with sensor removal.
4
Remove crankshaft position sensor mounting bolt
Using an 8mm socket, remove the single bolt securing the crankshaft position sensor to the engine block. The bolt may have thread-locking compound applied. Keep the bolt if it is in good condition, otherwise replace with new hardware.
Torque spec
Crankshaft Position Sensor10 Nm (7 lb-ft)
5
Extract sensor from engine block
Carefully pull the sensor straight out from the engine block bore. The sensor may be tight due to the O-ring seal. If stuck, gently rotate the sensor body while pulling to break the seal. Do not pry against the sensor body or engine block surfaces. The sensor extends approximately 30-40mm into the block.
⚠Do not use excessive force or pry tools that could damage the sensor bore in the engine block. Damage to the bore will require costly engine block repairs.
6
Inspect sensor bore and clean mounting surface
Inspect the sensor bore in the engine block for any debris, metal particles, or oil contamination. Clean the bore opening with electrical contact cleaner on a lint-free cloth. Check the condition of the O-ring sealing surface on the engine block for scratches or damage. The bore must be clean and dry for proper sensor operation.
7
Prepare new sensor for installation
Remove the new crankshaft position sensor from packaging. Verify that the new O-ring seal is properly seated in the groove on the sensor body. Apply a light coating of clean engine oil to the O-ring to ease installation. Do not use any sealant or adhesive on the O-ring or sensor body.
8
Install new crankshaft position sensor
Carefully insert the new sensor into the engine block bore, ensuring it enters straight without cocking to one side. Push the sensor in until it seats fully against the engine block mounting surface. The sensor tip must be positioned at the correct depth to maintain proper air gap with the crankshaft reluctor ring.
9
Install and torque sensor mounting bolt
Thread the sensor mounting bolt by hand to ensure proper thread engagement. Using a torque wrench and 8mm socket, tighten the bolt to specification. This bolt secures the sensor and maintains proper positioning relative to the crankshaft.
⚠Over-torquing the sensor mounting bolt can crack the sensor housing or strip threads in the aluminum engine block. Use a calibrated torque wrench.
Torque spec
Crankshaft Position Sensor10 Nm (7 lb-ft)
10
Reinstall wire harness bracket
Secure the sensor wire harness using the plastic bracket or clip removed earlier. Ensure the harness routing matches the original path and that no wires contact hot exhaust components or moving parts. The harness should have slight slack to prevent tension on the sensor connection.
11
Reconnect electrical connector
Connect the electrical connector to the crankshaft position sensor, ensuring it locks into place with an audible click. Verify the connection is secure by gently pulling on the connector body. Check that the connector seal is properly seated to prevent moisture intrusion.
12
Reinstall undercover panels
Reinstall all engine undercover panels removed during preparation. Ensure all fasteners are properly tightened and no tools or parts have been left in the engine compartment or underneath the vehicle.
13
Reconnect battery and clear fault codes
Lower the vehicle and reconnect the negative battery terminal. Using a Mercedes-Benz compatible diagnostic scanner, clear any stored crankshaft position sensor fault codes (P0335, P0336, or similar). This ensures the ECU will properly relearn sensor values during the test drive.

Reassembly

Ensure all electrical connections are secure and properly routed away from heat sources
Verify the sensor mounting bolt is torqued to specification (10 Nm / 7 lb-ft)
Double-check that no tools or parts remain underneath the vehicle
Confirm all engine undercover panels are securely fastened

Verification

Start the engine and verify it runs smoothly without rough idle or misfires
Check that no crankshaft position sensor fault codes are present using a diagnostic scanner
Perform a test drive and verify smooth acceleration with no hesitation or stalling
Monitor engine RPM gauge during idle - it should display a stable reading between 600-700 RPM
Verify that the Check Engine Light (MIL) does not illuminate after clearing codes
Re-scan for fault codes after test drive to confirm no new sensor-related codes have been stored