BMW 1999-2005 M3 Service Manual page 1236

On-Board Diagnostics
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Specific cylinder(s)
Severity of the misfire event
Emissions relevant or catalyst
damaging
Misfire detection is an on-going
monitoring process that is only
disabled under certain limited
conditions.
Secondary air injection monitoring:
Secondary air injection is used to
reduce HC and CO emissions during
engine warm up. Immediately following
a cold engine start (-10 to 40�C),
fresh air/oxygen is pumped directly into
the exhaust manifold. By injecting
oxygen into the exhaust manifold,
catalyst warm-up time is reduced.
System components:
Electric air injection motor/pump
Electric motor/pump relay
Non-return valve
Vacuum/vent valve
Stainless steel air injection pipes
Vacuum reservoir
The secondary air system is monitored
via the use of the pre-catalyst oxygen
sensors. Once the air pump is active
and air is injected into the system, the
signal at the oxygen sensor will reflect
a lean condition. If the oxygen sensor
signal does not change, a fault will be
2/25/2009 11:22 PM