BMW 3 (E46). Instruction - page 77

Component

Condition

Test

Repair

Secondary circuit

Wet coil
Corroded coil
connections

Secondary circuit

Check for water leak.
Check resistance
values (see

Table

e

).

Ignition coil

Primary or secondary
circuit on or shorted
Housing cracked,
damaged

Primary and
secondary circuits
(see

Table e

)

Replace coil as
necessary.

Ignition coil harness
connector

Power supply,
primary control circuit
or ground (shunt
signal) circuits
impaired

Primary ignition and
terminal 4A feedback
preset measurements

Look for open, loose
connector, corrosion,
crossed or damaged
connector pins.
Inspect ignition
unloader relay.
Replace coils as
necessary.

Warnings and cautions

The engine management system
contains sensitive electronic components.
To protect the system and for general
safety, the following warnings and
cautions should be observed during
ignition system troubleshooting,
maintenance or repair work.

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 extreme caution
when working on a car with the
ignition switched on or the engine
running.

Connect and disconnect the 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.

CAUTION!

Prior to disconnecting the battery,
read the battery disconnection
cautions given at the front of this
manual on page viii.

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
disconnected.

Do not disconnect the battery
while the engine is running.

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.

120-2

Ignition System Service

Ignition firing order

Each ignition coil is mounted above the
corresponding spark plug. Cylinder 1 is
at the front of the engine.

Ignition firing order

M52 TU/M54
engine

1 - 5 - 3 - 6 - 2 -

4

Disabling ignition system

The ignition system operates in a lethal
voltage range and should therefore be
disabled any time engine service or
repair work is being done that requires
the ignition to be switched on.

The engine management system can be
disabled by removing the DME main
relay (arrow). The relay is located in the
electronics box (E-box) in the left rear of
the engine compartment.

CAUTION!

Relay locations may vary. Use care
when identifying relays. The main
relay has a large (4 mm 2) red wire at
terminal 30 and a large (4 mm 2)
red/white wire at terminal 87. See

610 Electrical Component Locations

.

Checking for spark

CAUTION!

If a spark test is done incorrectly,
damage to the Engine Control Module

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