A Guide to the Engine Crankshaft Position Sensor for the 2007-2017 Mercedes-Benz S550
If your S550 won't start or stalls when hot, the crankshaft position sensor is a likely culprit; here's what you need to know before you buy a replacement.
- A primary symptom of failure is the engine stalling when hot and refusing to restart until it has cooled down.
- Due to the critical nature of this sensor, it is highly recommended to use an OEM or a premium aftermarket brand like Bosch or Hella.
- The sensor is located in a very tight space on the driver's side bell housing, making replacement difficult without the right tools and patience.
- No special programming is needed after installation; it is a plug-and-play component.
Understanding Crankshaft Position Sensor Failure in Your S550
The crankshaft position sensor (CPS) is a known failure point on many Mercedes-Benz vehicles, including the S550. Due to its location, it is exposed to intense engine heat, which can cause the internal electronics or plastic housing to fail over time. When it fails, it typically does so when the engine is hot, leading to a frustrating no-start condition that resolves after the engine cools down. This can leave you stranded without warning. While a recall was issued for this sensor on some 2006-2008 *diesel* models, it did not apply to the gasoline-powered S550. No specific recalls or widespread Technical Service Bulletins (TSBs) for the S550's crankshaft sensor were found in searches.
Choosing the Right Aftermarket Sensor: Quality Matters
For sensitive electronics on a Mercedes-Benz, the quality of the replacement part is critical. While OEM (Original Equipment Manufacturer) is always a safe bet, high-quality aftermarket parts from OEM suppliers can offer comparable performance at a better price. However, owner and mechanic forums consistently warn against using cheap, unknown aftermarket sensors on these vehicles. A low-quality sensor can fail quickly, provide an incorrect signal leading to poor performance, or even be dead on arrival.
Brand Tiers for Your Consideration
- Premium Aftermarket (OEM Suppliers): Brands like Bosch, Hella, and sometimes Delphi are often the original suppliers to Mercedes-Benz. These parts are expected to provide performance and longevity that is very close to the original part. Forum users generally recommend sticking to these brands for critical sensors.
- Standard Aftermarket: Brands such as Standard Ignition (SMP), NGK/NTK, and Walker Products often produce reliable parts that meet or exceed original specifications. They are a solid choice if a premium brand is not available.
- Economy Aftermarket: This tier includes many lesser-known or private-label brands. While the price is attractive, the quality can be inconsistent. For a critical sensor like the CPS, which can leave you stranded and is labor-intensive to replace, opting for an economy part is a significant risk.
Installation & Cost Information
The crankshaft position sensor is located on the back of the engine, on the driver's side, near the bell housing where the engine meets the transmission. Access is very tight, requiring the removal of the engine air filter housing. The job is performed mostly by feel. It is held in by 🎬 Follow this step-by-step DIY guide for replacing your crankshaft sensor. a single E8 or T30 Torx bolt, depending on the specific year and engine. While the part itself is not expensive, professional installation is recommended for those not comfortable working in tight, blind spaces.
| Item | Estimated Cost |
|---|---|
| New OEM Part | $89.00 - $175.00 |
| New Aftermarket Part | $24.74 - $108.98 |
| Shop Labor | $100 - $250 |
A Note on Seized Sensors
On older or high-mileage vehicles, particularly those with the earlier all-metal sensor bodies, the sensor can corrode and seize in the engine block. This can turn a simple job into a major repair, sometimes even requiring transmission removal to gain access to break it free. Applying a small amount of anti-seize compound to the body of the new sensor (avoiding the tip) can help prevent this.
Frequently Asked Questions (FAQ)
Do I need to reprogram the computer after replacing the sensor?
No, a crankshaft position sensor replacement on the 2007-2017 S550 does not require any special programming or recalibration. It is a plug-and-play part.
What tools are needed to replace the S550 crankshaft sensor?
You will need a ratchet with several long extensions, a universal joint, and either an E8 external Torx socket or a T30 Torx socket. The exact bolt type can vary, so it's best to confirm before starting. A mirror and a good light source are also essential for locating the sensor.
Can a bad crankshaft sensor cause transmission problems?
Yes, indirectly. A faulty signal from the crankshaft sensor can cause erratic engine behavior that may feel like a transmission issue, such as bad shifting or slipping. The engine's computer relies on this signal for overall vehicle operation, and incorrect data can confuse other systems.
Why did my car stall when it got hot but restart after cooling down?
This is a classic symptom of a failing crankshaft position sensor. The electronic components inside the sensor break down when exposed to high engine temperatures, causing the signal to cut out. Once the sensor cools, the connection is temporarily restored, and the car will start again until it heats up.
Helpful Videos
Technical Specifications
OEM Part Numbers: 6429050000 2729050000 2769051400
Typically held in by a single E8 or T30 Torx bolt. Located on the driver's side of the engine bell housing.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Mercedes-Benz S550: