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BMW VANOS System

Design & Common Faults

BMW engines have been equipped with VANOS (VAriable  NOckenwellen Steuerung, German for variable valve timing) starting in 1993. The first application of VANOS was on the M50 6-cylinder engine in the 5 Series (E34). Since that time there have been three major versions of VANOS systems and multiple variations.

The major categories are:

Single VANOS 6-cylinder M50, M52 and S52 engines, 1993 - 2000
V8 M62TU engine, 1999 - 2003
Double VANOS

6 cylinder M52 TU, M54 and S54 engines, 1999 -2005

6-cylinder N54, 2004 - 2010

Double VANOS with Valvetronic 6-cylinder N52 N55, 2004 - 2010 
V8 N62 and N62 TU engines, 2004 – 2010
 V12 N73 and N74 engines, 2005 - 2015

In the sections below, we describe the basic features of each VANOS version. Keep in mind that, as with many drivetrain components, systems and functions, VANOS is increasingly integrated in the engine management systems (DME). When you are fault finding and troubleshooting the DME, starts with the use of factory diagnostic system or equivalent scan tool. Also, as in all diagnostic situations, verify that the basics -- engine mechanical condition, fuel supply and electrical power supply -- are within the correct range before attempting to diagnose complex electronic or mechanical systems.

Single VANOS

Single VANOS

In this system, only the timing on the intake camshaft is varied. A VANOS solenoid, operated by engine oil pressure and controlled by the engine control module (ECM), advances and retards intake valve timing by rotating the modified camshaft sprocket assembly. At low engine speeds, intake valves open late, ensuring smooth engine operation. As engine speed increases into the mid-range, valve timing is advanced by the modified camshaft sprocket, resulting in increased torque, improved drivability and reduced emissions. At higher engine speeds, intake valve timing is once more retarded, resulting in better power and performance.

In 6-cylinder engines with single VANOS (M50, M52, S52), intake camshaft timing advance and retard are either on or off. There is no middle ground.
In V8 models (M62 TU), there is a separate intake camshaft solenoid for each bank of the engine. Intake camshaft timing is infinitely variable within the range of the VANOS solenoids.
When repairing this system, be sure to set up valve timing and the timing chains very carefully. Placement of the VANOS sprocket and control unit are critical. Be sure to have the correct repair manual at hand when attempting repairs to this system.

Single VANOS systems can experience common failures and symptoms.

  • P1519 (BMW 212, 0xD4): VANOS mechanically stuck (jamming). Most times the driver will note loss of drivability, engine torque and horsepower. Most times the symptoms are worse at low RPM or when the engine is cold and when cold also accompanied by a rattle noise at start. Horsepower and torque loss noticeable during acceleration and a drop in fuel economy.

A quick test for rough idle on M52 engines (1999-2000 MY). Unplug the VANOS actuator solenoid electrical connector. If the rough idle subsides, the fault is in the VANOS actuator.

The fix here is to rebuild the VANOS actuators using available rebuild kits or replacing the VANOS actuator units. Always confirm engine oil level, condition and pressure are OK.

Double VANOS

Double VANOS

The first version of this system, introduced in the 1999 M52 TU engine (E46 3 Series), is fully variable (as opposed to on-off only, as in the single VANOS system) and operates on both the intake and exhaust camshafts. Single VANOS offered smooth idle and increased torque at low and medium rpm. Double VANOS offers the same advantages and in addition, by advancing or retarding exhaust camshaft timing, offers an internal exhaust gas recirculation (EGR) feature which lowers nitrogen oxide (NOX) emissions, as well as quicker warm-up for the catalytic converter(s) and faster reduction in exhaust emissions.

Camshaft timing changes are actuated by solenoids powered by engine oil pressure and controlled by the ECM.

In the M series of engines (M52 TU, M54, M56), one solenoid is used to control the timing of each camshaft.
On the N54 and S54 engine the timing of each camshaft is controlled by two solenoids, one to retard and the other to advance the timing.
Removal and installation of the VANOS unit on these engines requires the use of special BMW camshaft timing tools and techniques. With the use of these tools, camshaft timing and VANOS installation is relatively straightforward.

Some variations of this system are called dual-VANOS.

Dual-VANOS systems can experience common failures and symptoms. Most times fault codes are stored, generally for the exhaust VANOS actuator. The VANOS actuator utilizes a stronger piston spring, so failures are noticed by the DME sooner. However the intake VANOS actuator can also set faults for the same symptoms below.

  • P1520 (BMW 104, 0x68): B (exhaust) Camshaft Position Actuator (faulty reference value).
  • P1523 (BMW 106, 0x6A): B (exhaust) Camshaft Position Actuator Tight or Jammed (mechanically stuck).
  • P1397 (BMW 18, 0x12): Camshaft Position Sensor B (exhaust) Circuit. (if sensor has been replaced multiple times for this fault code, the VANOS actuator is likely the cause.)
  • On 2001+ M54 & M56 P1397 B (exhaust) Camshaft Position Actuator (faulty reference value). B (exhaust) Camshaft Position Actuator Tight or Jammed (mechanically stuck).

Most times the driver will note loss of drivability, (engine torque and horsepower), rough idle and hard starts or stalling when cold. Most times the symptoms are worse at low RPM or when the engine is cold and when cold also accompanied by a rattle noise at start. Horsepower and torque loss noticeable during acceleration and a drop in fuel economy.

The fix here is to rebuild the VANOS actuators using available rebuild kits or replacing the VANOS actuator units. Always confirm engine oil level, condition and pressure are OK.

Double VANOS with Valvetronic

Double VANOS with Valvetronic

N series of engines (6-cylinder N52 and N55; V8 N62 and N62 TU; V12 N73, N73 TU and N74) incorporate BMW’s variable valve-lift technology called Valvetronic. Each intake valve (2 per cylinder) is opened not directly by the corresponding camshaft but by an additional mechanism which varies the valve lift. Engine power is not controlled by the throttle valve but by intake valve lift. This system results in increased engine power and torque and reduced emissions.

Valvetronic and double VANOS are a tandem pair of technologies. VANOS components are compact and infinitely variable sprockets which electrohydraulically adjust valve timing to enhance mid-range performance. Both Valvetronic and VANOS are actuated by engine oil pressure and controlled by the ECM.

Removal and installation of these complex mechanisms requires care and special tools. Be sure to acquire the correct repair manuals and tools before attempting disassembly. But it is also noteworthy that with the correct tools and information, reassembly of these components is relatively straightforward.

N-Series or NG6 engines Exhibit similar symptoms and faults as mentioned above. Rough idle, noise cold and stalling, misfire codes, etc. The newer engines have a problem with sludge and debris build-up in the VANOS solenoids. The solenoids can be removed, cleaned and reinstalled to test. If the same fault codes return, check mechanical engine timing. Use camshaft and crankshaft alignment tools to confirm engine timing is out of sync. Most times due to worn timing chain guides, causing incorrect engine timing.

Common 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. Exhaust, cold start
  • 2A99 Crankshaft - Exhaust camshaft, reference
  • 2A87 Exhaust Vanos, mechanism