Driveability Troubleshooting; Dme System Voltage - BMW 1999-2005 M3 Service Manual

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Driveability
Troubleshooting
The Siemens systems are
sophisticated self-diagnosing OBD II
systems. These systems continuously
monitor components and record and
store valuable diagnostic information.
If the `Check Engine' or `Service
Engine Soon' light [also known as the
malfunction indicator lamp (MIL)] is
illuminated, the first diagnostic test
should be to hook up a
BMW-compatible scan tool and check
the fault memory.
The powerful diagnostic capabilities of
these systems have the potential to
save hours of diagnostic time, incorrect
component replacement and possible
damage to system components. See
OBD On Board Diagnostics
back of this manual.
Two of the most common causes of
driveability problems are system
voltage levels and poor grounds.
System voltage
The DME system requires that the
system (battery) voltage be maintained
within a narrow range. Voltage levels
outside the operating range can cause
havoc. When troubleshooting an
illuminated MIL, make sure the battery
is fully charged and capable of
delivering all its power to the electrical
system.
To make a quick check of the battery
charge, measure the voltage across the
battery terminals with all cables
attached and the ignition off. A fully
charged battery will measure 12.6 volts
or slightly more, compared to 12.15
100-2
at the
2/25/2009 9:59 PM