In early model BMW's, such as our favorite E30 M3, engine timing adjustments had to be done by hand with a special tool. The crankshaft was responsible for spinning gears which spins the cams which controls timing. Because of this, you were limited to either low end torque or high end power, but it was very difficult to design a crankshaft that provided both. So tuners would frequently upgrade their crankshaft to provide the performance they are looking for, on the street or on the track.
Variable valve timing is the solution to this problem, and just about every manufacturer has their own technology for it. Variable valve timing allows for timing adjustments to be made electronically and automatically, instead of manually by hand like they had to do back in the day. The end result is a smoother power bank, torque on the low end without comprising power on the high end, and overall just better driveability, smoother idling, etc.
The VANOS system is BMW's technology that allows for variable valve timing. It isn't revolutionary, if you've ever heard a Honda bro (hilarious youtube video) yell "VTEEEEC", he is talking about the same technology as Vanos.
How does the BMW VANOS System Work?
The Vanos system uses oil pressure to control the position of the intake and exhaust camshafts. The system uses a gear on the Vanos actuator and a gear on the camshaft. A solenoid then controls the amount of oil pressure being applied which controls the movement of the cam gear outward or inward, effectively controlling the timing of the valves.
Here is a picture of what the gear looks like on the actuator:
This gear slides inwards and outwards to control timing. When the car is at idle, the gear is fully inward or retracted, and it will begin to slide outward as throttle is given. As you accelerate, the Vanos solenoid begins to close off, which causes the gear to slide outwards. Here is a picture of how that works:
The 3 Types of Vanos Systems
Since you aren't yet confused from the above, there are three different Vanos systems used by BMW as the technology has evolved: single vanos, dual vanos, and dual vanos with valvetronic. For the sake of complexity, I'm not going to get into how the systems are different. Instead, lets focus on which cars use which system, and what the engine fault codes are for each.
1. Single Vanos
On the single Vanos system, the intake camshaft timing is the only timing that is variable. This system does not adjust the exhaust camshaft. The single vanos systems opens the intake camshaft late at low engine speeds to ensure smooth idling and performance. As engine speed increases, the valves open further resulting in increased torque and improved driveability. Think of this as cruising speed. When you put your foot to the floor, the intake valves fully open, resulting in more power and higher performance.
What BMW's Use the Single Vanos System?
- M50 engine ('93-'00)
- M52 engine ('93-'00)
- S52 engine ('93-'00)
- M62 V8 engine ('93-'03)
Single Vanos Engine Fault Codes
- P1519 (BMW 212 0xD4)
This engine fault code means that the Vanos system is getting stuck and jamming up
Single Vanos Failure Symptoms
- Loss of driveability
- Decreased horsepower and torque
- Rough idling and sometimes a rattling noise
- Poor fuel economy
How to Diagnose and Repair a Failed Single Vanos Unit
If you are experiencing rough idling you can unplug the electrical connector on the Vanos actuator solenoid. If you continue to experience rough idling after unplugging this connection, then it is likely a faulty Vanos actuator.
The only fix here is to rebuild the Vanos actuators using a rebuild kit or to replace the full unit.
2. Dual Vanos
The dual Vanos system controls the valves on both the intake and exhaust camshafts. The camshafts are controlled by Vanos Solenoids. The benefit to controlling the exhaust camshaft is improved emissions, aka less emissions, along with a quicker engine warm up time. The intake camshaft works the same as the single Vanos and opens up as more throttle is given. The dual Vanos is the system used on the infamous N54, and is very prone to failure in these engines. Fortunately repair is a lot easier.
What BMW's Use the Dual Vanos System?
- M52 engine ('99-'05)
- M54 engine ('99-'05)
- S54 engine ('99-'05)
- N54 engine ('04-'10)
Dual Vanos Engine Fault Codes
- P1520 - camshaft position actuator
- P1523 - camshaft position actuator
- P1397 - camshaft position sensor circuit (this can be caused by a faulty sensor. If you've replaced the sensor and still get it, then it is the solenoids)
- 2A82: intake camshaft (solenoid)
- 2A87 exhaust camshaft (solenoid)
The 2A82 and 2A87 fault codes are guarantees that your solenoids have gone bad. The "P" fault codes are commonly caused by Vanos failures, but can also be caused by other things such as the actuator or a sensor.
We recommend replacing your solenoids if you are getting any of these codes. Replacing the Vanos solenoids is a relatively easy DIY. These things tend to get gunked up and go bad around 50,000 miles, and are commonly operating well below 100% by the time you hit 70,000 miles. Replacing them should restore low-end power and improve fuel efficiency, even if you aren't getting any fault codes.
Parts for N54 Vanos Repair
We recommend the URO Solenoids if you are going to do a DIY repair and looking for a good budget option. If you want a pricier but top quality brand then we recommend Pierburg. They are about half the cost of the Genuine parts and in our opinion are better as the Genuine ones fail frequently.
URO/Pierburg Solenoids for N54: https://bmwsparkplugs.com/products/bmw-vanos-solenoid-11-36-7-585-425
Dual Vanos Failure Symptoms
- Loss of torque and power in the lower range
- Hesitation or slow reaction time when you press the peddle
- Idle hiccups or a constant rough idle
- Slow cold starts
- Limp mode after acceleration
How to Diagnose and Repair a Failed Dual Vanos Unit
Unlike the single vanos which usually needs to be fully replaced or rebuilt, the majority of the time only the solenoids need to be replaced. One additional option is to try to clean your solenoids, which is a simple process but is only a temporary fix. If you want to try to get a little more life out of your solenoids and save money on the front end, then I recommend trying to clean them before replacing them. There is a good DIY for that here: https://www.e90post.com/forums/showthread.php?t=486201
If you are going to replace your solenoids you can use the same DIY and just pop the new ones in vs. cleaning and putting the old ones back in.
3. Dual Vanos with Valvetronic
Vanos adjusts the valve timing, or when the valves open and close. Valvetronic is responsible for adjusting valve lift, which is how open the valves are. By combining the two together, you get optimal performance and driveability, increased horsepower, improved fuel economy and better emissions. Valvetronic also negates the need for a throttle body. Vanos and Valvetronic work together and are both controlled by the ECM and powered by engine oil pressure.
What BMW's Use Dual Vanos and Valvetronic?
- N52 engine ('2004-'2010)
- N55 engine ('09-'Present)
- N62 engine ('04-'10)
- N73/74 engine ('05-'15)
Dual Vanos with Valvetronic Engine Fault Codes
- P0011 - A Camshaft Position: Timing Over-Advanced or System Performance (Bank 1)
- P0012 - A Camshaft Position: Timing Over-Retarded (Bank 1)
- P0014 - B Camshaft Position: Timing Over-Advanced or System Performance (Bank 1)
- P0015 - B Camshaft Position: Timing Over-Retarded (Bank 1)
- P0020 - B Camshaft Position Actuator Circuit (Bank 2)
- P0021 – A - Timing Over-Advanced or System Performance (Bank 2)
- P0022 - A Camshaft Position: Timing Over-Retarded (Bank 2)
- P0024 - B Camshaft Position: Timing Over-Advanced or System Performance (Bank 2)
- P0025 - B Camshaft Position: Timing Over-Retarded (Bank 2)
- 2A7A DME: Variable camshaft timing control
- 2A99 Crankshaft - Exhaust camshaft
- 2A87 Exhaust Vanos
- 2A82 Intake Vanos
Dual Vanos with Valvetronic Failure Symptoms
- Poor and rough idling
- Loss of lower range power
- Cold start issues and noises
- Engine stalling at idle
- Hesitation or limp mode under acceleration
How to Repair a Failed Dual Vanos w/Valvetronic Unit
With the addition of valvetronic, repairing and fixing issues is rather difficult compared to the dual vanos only systems. Fortunately, BMW upped their warranty on the Vanos systems to 10 years for cars with double vanos and valvetronic. Because of this, there aren't many DIY guides out there, especially due to the difficulty of repair. If you need to take it to a shop and pay for the repair, at least save some money and buy the solenoids below.