BMW 1999-2005 M3 Service Manual page 1234

On-Board Diagnostics
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required tests. The ECM must
recognize the loss or impairment of the
signal or component and determine if a
signal or sensor is faulty based on 3
conditions:
Signal or component shorted to
ground
Signal or component shorted to
B+
Signal or component missing
(open circuit)
The OBD II system must monitor all
emission control systems that are
on-board. Not all vehicles have a full
complement of emission control
systems. For example, a vehicle may
not be equipped with secondary air
injection, so naturally no secondary air
readiness/function code would be
present.
OBD lI requires monitoring of the
following:
Oxygen sensor monitoring
Catalyst monitoring
Misfire monitoring
Evaporative system monitoring
Secondary air monitoring
Fuel system monitoring
Monitoring these emissions related
functions is done using DME input
sensors and output accouters based
on preprogrammed data sets. If the
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