BMW 535i xDrive (2009-2016) Engine Coolant Temperature Sensor Guide
Keep your N55 engine running smoothly by understanding coolant temp sensor failures and choosing the right replacement part.
- A failing ECT sensor can cause a Check Engine Light, poor fuel economy, overheating, and hard starting.
- Your N55 engine has multiple temperature sensors; proper diagnosis is key to replacing the correct part.
- For best results, choose a Genuine BMW part or an aftermarket sensor from a known OEM supplier like Delphi or Vemo.
- The replacement is DIY-friendly, but you must bleed the cooling system afterward to remove any air pockets.
Symptoms of a Failing ECT Sensor in Your 535i xDrive
A bad coolant temperature sensor on the N55 engine can cause a variety of problems. Because the DME relies on this sensor for so many calculations, a false signal can lead to confusing symptoms. Watch for these common signs:
- Check Engine Light: This is often the first sign. The DME will detect an illogical signal from the sensor and store a fault code.
- Poor Fuel Economy: If the sensor incorrectly tells the DME the engine is cold, the computer will enrich the fuel mixture, causing the car to use more gas than necessary.
- Engine Overheating or Running Too Cool: A faulty sensor can fail to trigger the cooling fans when needed, leading to overheating. Conversely, it might cause the fans to run at full speed constantly, even when the engine is cold, preventing it from reaching its proper operating temperature. 🎬 Learn how to fix a sensor stuck on a cold reading.
- Black Smoke from Exhaust: A very rich fuel mixture, caused by a sensor stuck in a "cold" reading, can result in unburned fuel igniting in the exhaust, producing black smoke.
- Hard Starting: The DME needs an accurate temperature reading to provide the correct fuel mixture for starting a cold or hot engine. A bad reading can make the car difficult to start.
- Erratic Gauge Readings: Some owners report seeing impossible temperatures like -128°C in the hidden menu, which is a clear sign of sensor or wiring failure.
Multiple Temperature Sensors
Your BMW N55 engine has more than one sensor related to temperature. There is a main Engine Coolant Temperature (ECT) sensor, often located on the cylinder head near the oil filter housing. There is also a temperature sensor built into the thermostat assembly and another for oil temperature. It's important to diagnose the correct failing sensor before ordering parts.
Choosing the Right Aftermarket ECT Sensor
When it comes to sensors for a complex vehicle like the 535i xDrive, quality matters. While a Genuine BMW part is always an option, several reputable aftermarket brands offer reliable parts, some of which are the original equipment manufacturers (OEM) for BMW.
Brand Tiers for Your BMW
- Tier 1 (OEM/OE Equivalent): Brands like Delphi and Vemo are often original equipment suppliers to BMW. Choosing these brands gives you a part that is essentially identical to the dealer part without the dealer price tag. They are built to the exact specifications required by your vehicle's sensitive electronics.
- Tier 2 (High-Quality Aftermarket): Brands such as Standard Ignition (SMP), NGK, and Beck Arnley have a strong reputation for producing quality components that meet or exceed OEM specifications. These are a solid choice for a reliable repair.
- Tier 3 (Budget-Friendly): Brands like Facet, Four Seasons, and Walker Products offer a more affordable price point. While functional, for a critical sensor on a high-performance engine, many BMW owners and mechanics recommend sticking with OEM or top-tier aftermarket brands to avoid potential compatibility issues.
Pro Tip: When replacing the sensor, it's a good idea to also replace the small O-ring or sealing washer to prevent coolant leaks. Some replacement sensors include this, but it's wise to check.
Known Issues, Recalls & TSBs
As of late 2024, there are no specific recalls or Technical Service Bulletins (TSBs) for the engine coolant temperature sensor itself on the 2009-2016 BMW 535i xDrive. However, there are related recalls and service actions for the cooling system.
- NHTSA Recall 24V-608: This recall affects some 2012-2016 5-series models (specifically with the 4-cylinder N20/N26 engine, not the 6-cylinder N55 in the 535i) for a water pump electrical connector that can short circuit. While not directly for the 535i, it highlights the complexity of BMW cooling systems.
- Thermostat Service Action: BMW issued a service action (SB-10057339-2098) for some models due to moisture causing corrosion on the thermostat's electrical contacts, which can lead to faults. Since the thermostat and ECT sensor work together, a thermostat issue can sometimes be misdiagnosed as a sensor problem.
| Item | Estimated Cost |
|---|---|
| New Aftermarket Part | $19 - $69 |
| New OEM Part | $45 - $70 |
| Shop Labor | $90 - $180 |
| Total (Aftermarket Part + Labor) | $109 - $249 |
Frequently Asked Questions (FAQ)
Where is the engine coolant temperature sensor located?
On the N55 engine in your 535i xDrive, the main engine coolant temperature sensor is typically located on the cylinder head, near the oil filter housing. It is a small, two-wire sensor that screws into the head. 🎬 See the exact location of the sensor on the N55 engine. Be aware there are other temperature sensors, including one integrated into the thermostat housing.
Is this a difficult DIY replacement?
For a moderately experienced DIYer, this is a manageable job. The sensor is usually accessible after removing some engine covers. The main challenges are not over-tightening the new sensor (it can break) and dealing with minor coolant spillage. The cooling system will need to be bled of any air that enters the system afterward.
Do I need to drain the coolant to replace the sensor?
While the official procedure is to drain the coolant, many people replace the sensor without a full drain. If the engine is completely cold, you can quickly swap the old sensor for the new one with minimal coolant loss. Have the new sensor ready to go to plug the hole immediately. You will still need to top off the coolant and bleed the system.
Should I buy an OEM sensor or is aftermarket okay?
For this specific part on a BMW, it is highly recommended to use either a Genuine BMW part or a part from a known OEM supplier like Delphi or Vemo. These cars can be sensitive to sensor voltage and resistance, and using a lower-quality part may not solve the problem or could fail prematurely.
Helpful Videos
![[SOLVED & FiXED] BMW Engine Coolant Sensor STUCK on Cold Temp #diyrepair #mechanic](https://img.youtube.com/vi/gJDSCefjTUA/mqdefault.jpg)
Technical Specifications
OEM Part Numbers: 13621433076 13627580635
Typically a 2-pin, plug-in sensor that screws into the cylinder head.
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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.
- BMW 535i xDrive: