BMW 5251 Service Manual page 271

Camshaft Timing Chain
1
VANOS
I
4
When engine is started, camshafts are in deactivated
camshaft
retarded Engine
I
i
oil supply
position:
.
lntalte camshaft is held in RETARDED position by oil
pressure.
Exhaust camshaft is held in ADVANCED position by
preload spring and oil pressure.
VANOS
Piston
out
ECM
Piston in
Within 2
-
5 seconds (50 engine revolutions), the ECM begins
monitoring and controlling camshaft positions.
The Double VANOS system allows full variability of camshaft
timing up to the limits of the system. When the ECM detects
that the camshafts are in optimum position, the solenoids are
modulated at approximately 100
-
220 Hz to maintain oil pres-
sure on both sides of the actuator pistons to maintain timing.
In models with DME MS 43.0 (model year2001 and newer),
the engine control module (ECM) detects camshaft position
before the engine starts, thereby adjusting camshaft timing
immediately upon start-up.
NOTE-
.
VANOS system troubleshooting and diagnostics is best
accomplished using a scan tool.
.
Diagnostic Trouble Codes (DTCs) pertaining to the
VANOS system are listed in the following table. See also
OED On-Board Diagnostics.
Elevated oil temperatures can cause VANOS to deactivate.
Oil that is too thick (high viscosity) may cause a DTC to be
set in the ECM. I f VANOS is deactivated (limp-home
mode), there will be a noticeable loss of power.
VANOS
fault codes
BMW
code P-code Fault description
19 PI529 V A N O S solenoid valve activation,
exhaust
21 PI525 V A N O S solenoid valve
activation,
intake
103 PI519 V A N O S faulty reference value
intake
104 PI520 V A N O S faulty reference value
exhaust
105 PI522 V A N O S stuck (Bank I ) intake
106 PI523 V A N O S stuck (Bank 2) exhaust