Warnings And Cautions; Engine Management - BMW 5251 Service Manual

120-3
Ignition
System
Warnings and cautions
The ignition system produces dangerous high voltage. In ad-
dition the sensitive electronic components can be damaged if
proper precautions are not adhered to.
WARNING-
* Do not touch or disconnect any cables from the coils while
the engine is running or being cranked by the starter.
The ignition system produces high voltages that can be
fatal. Avoid contact with exposed terminals. Use ex-
treme caution when working on a car with the ignition
switched on or the engine running.
-
Connect and disconnect tlie DME system wiring and
test equipment leads only when the ignition is OFF:
Before operating the starter without starting the engine
(for example when making a compression test) always
disable the ignition.
CA
U
TIOW-
Do not attempt to disable the ignition by removing the coils
from the spark plugs.
Connect or disconnect ignition system wires, multiple
wire connectors, and ignition test equipment leads only
while the ignition is off Switch multimeter functions or
measurement ranges only with the test probes discon-
nected.
*
Do not disconnect the battery while the engine is run-
ning.
A high impedance digital multimeter should be used for
all voltage and resistance tests. An LED test light
should be used in place of an incandescent-type test
lamp.
In general, make test connections only as specified by
BMW as described in this manual, or as described by
the instrument manufacturer.
Engine management
BMW
€39
engines use an advanced engine management
system known as Digital Motor Electronics (DME). DME in-
corporates on-board diagnostics, fuel injection, ignition and
other engine control functions. DME variants are listed in
Table a. Engine management systems.
Second generation On-Board Diagnostics (OED I I ) is incor-
porated into the engine management systems used on the
cars covered by this manual. Use a BMW-specific electronic
scan tool, or a "Generic" OED I I scan tool to access Diagnos-
tic Trouble Codes (DTCs). DTCs can help pinpoint ignition
ine management problems.