BMW 1999-2005 M3 Service Manual page 1237

On-Board Diagnostics
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set and identify the faulty bank(s). If
after completing the next cold start a
fault is again present, the MIL will be
illuminated.
Fuel system monitoring: This monitors
receives high priority. It looks at the
fuel delivery needed (long/short term
fuel trim) for proper engine operation
based on programmed data. If too
much or not enough fuel is delivered
over a predetermined time, a DTC is
set and the MIL is turned on.
Note:
Fuel trim refers to adjustments to base
fuel schedule. Long-term fuel trim
refers to gradual adjustments to the fuel
calibration adjustment as compared to
short term fuel trim. Long term fuel trim
adjustments compensate for gradual
changes that occur over time.
Fuel system monitoring monitors the
calculated injection time (ti) in relation
to engine speed, load, and the
pre-catalytic converter oxygen
sensor(s) signals as a result of residual
oxygen in the exhaust stream.
The diagnostic executive uses the
precatalyst oxygen sensor signal as a
correction factor for adjusting and
optimizing the mixture pilot control
under all engine operating conditions.
Evaporative system monitoring: This
monitor checks the sealed integrity of
the fuel storage system and related
fuel lines.
This monitor has the ability to detect
very small leaks anywhere in the
system. A pressure test is be
performed on the EVAP system on a
continuous basis as the drive cycle
allows.
On MS 42.0 cars, a leak detection
pump (LDP) is used to pressurize and
2/25/2009 11:22 PM