BMW Check Engine Light? Common Valvetronic System Failures in N55 & N20 Engines
The BMW N55 and N20 engines are well-regarded for their power and efficiency, but if you’ve encountered a check engine light or performance issues, your Valvetronic motor and eccentric shaft could be to blame. These components are essential for BMW’s variable valve timing system, and when they fail, they can cause serious drivability issues.
At CG Motorsports, we specialize in diagnosing and repairing BMW Valvetronic failures. In this guide, we’ll explain how the Valvetronic system works, common failure points, symptoms, and solutions to keep your BMW running smoothly.
What is the valvetronic system in BMWs?
BMW’s Valvetronic system is an advanced variable valve lift technology that optimizes fuel efficiency, reduces emissions, and improves throttle response. Instead of relying on a traditional throttle body, the Valvetronic system adjusts the intake valve lift through an eccentric shaft driven by a Valvetronic motor. While this technology enhances performance, it also introduces potential failure points.
Which BMW Models Have the N55 & N20 Engine?
The N55 engine was used in various BMW models between 2009 and 2019, including:
- BMW 135i (2011-2013)
- BMW 235i (2014-2016)
- BMW 335i (2010-2015)
- BMW 435i (2013-2016)
- BMW 535i (2010-2017)
- BMW X3 xDrive35i (2011-2017)
- BMW X4 M40i (2015-2018)
- BMW X5 xDrive35i (2011-2018)
- BMW X6 xDrive35i (2008-2019)
The N20 engine was commonly found in 2011-2017 BMW models, including:
- BMW 228i (2014-2016)
- BMW 320i / 328i (2012-2016)
- BMW 420i / 428i (2013-2016)
- BMW 520i / 528i (2011-2016)
- BMW X1 xDrive28i (2012-2015)
- BMW X3 xDrive28i (2012-2017)
- BMW X4 xDrive28i (2014-2017)
If you own one of these models and are experiencing Valvetronic system failures, CG Motorsports can help diagnose and fix the issue.
Common Causes of Valvetronic Failures in BMW N55 & N20 Engines
When you replace both the valve cover and the gasket, you’re ensuring a more durable and long-lasting solution to the oil leak. Here’s why:
1. Faulty Valvetronic Motor
The Valvetronic motor adjusts the eccentric shaft, controlling valve lift. Over time, heat, wear, and electrical issues can cause the motor to fail. Symptoms include:
- Check engine light
- Rough idling or stalling
- Loss of power
2. Worn or Misaligned Eccentric Shaft & Gears
The eccentric shaft is critical for Valvetronic operation. If it wears out or misaligns, it can disrupt the system, leading to severe engine performance issues. Symptoms include:
- Hesitation or misfiring
- Clicking or buzzing noises from the engine
- Reduced throttle response
3. Carbon Build-Up on Intake Valves
Since the N55 and N20 engines use direct injection, carbon build-up on the intake valves is common. Excess carbon can restrict airflow, causing Valvetronic malfunctions. Signs of this problem include:
- Rough idling
- Reduced fuel efficiency
- Delayed throttle response
4. Electrical & Wiring Issues
Faulty wiring, corroded connectors, or a failing ECU (Engine Control Unit) can interfere with Valvetronic function. Electrical issues may trigger diagnostic trouble codes (DTCs) related to the Valvetronic system, leading to unpredictable performance problems.
5. Software Malfunctions & Outdated ECU Programming
BMW frequently releases software updates to fix issues related to the Valvetronic system. Running outdated software may result in improper valve lift control, causing unnecessary strain on the system.
Symptoms of a Failing Valvetronic System
If your BMW’s check engine light is on, and you experience any of the following issues, you may have a Valvetronic system failure
- Check engine light (CEL) illuminated
- Rough idle or engine stalling
- Loss of power and throttle hesitation
- Higher fuel consumption
- Unusual buzzing or clicking noises from the engine
How to Fix and Prevent Valvetronic Failures
When you replace both the valve cover and the gasket, you’re ensuring a more durable and long-lasting solution to the oil leak. Here’s why:
1. Routine Maintenance & Inspections
Regular maintenance can prevent many Valvetronic motor and eccentric shaft failures. We recommend:
- Frequent oil changes using high-quality synthetic oil
- Periodic carbon cleaning with a Liqui Moly fuel system cleaner
- Engine flush treatments to reduce sludge buildup
2. Diagnostic Scans & Component Testing
If you suspect Valvetronic issues, bring your BMW to CG Motorsports for a full diagnostic scan. We’ll check for:
- Valvetronic motor faults
- Eccentric shaft wear
- Electrical and wiring issues
3. Updating BMW Software
Visit CG Motorsports to ensure your BMW’s ECU software is up to date. Software updates can resolve Valvetronic-related bugs and optimize system performance.
4. Professional Repairs & Replacements
If your Valvetronic motor or eccentric shaft has failed, our BMW-certified technicians can replace faulty components using OEM parts, ensuring long-term reliability.
Trust CG Motorsports for BMW Check Engine Light Diagnostics
Ignoring Valvetronic system issues can lead to costly repairs and decreased performance. If your BMW check engine light is on or you notice power loss, hesitation, or rough idling, don’t wait. CG Motorsports specializes in diagnosing and repairing BMW Valvetronic motor failures, eccentric shaft issues, and other common problems with N55 and N20 engines.
Book an appointment today and get back to enjoying the performance your BMW was designed for!
