Model: E46
Production: From Start of Production
E46 Power Supply
The power supply system in the E46 is used to supply power and ground to the various components and systems. Some of the components include
- Front power distribution box (fusebox)
- Battery and battery cables
- Grounding points
- Main fuse located in trunk
- Battery Safety Terminal
- Alternator (Generator)
Front Power Distribution
The main (front) fuse box is located behind the glovebox. The fuse panel is accessed by rotating two twist locks 90 degrees and allowing the fuse panel to drop into view. The fuse panel includes fuses 1 -71.
There are also two large fuses (red 50 Amp) which provide power for the IHKA blower and secondary air pump system.
Note. Always check the proper and most current ETM when checking fuses. Due to optional equipment and production changes, some fuse numbers and locations may vary.
Scheme 402
Located above the fuse panel, there are additional high amperage power distribution fuses (F101 -F107).
Scheme 403
This location differs from the E38/E39 in which these high amperage fuses were located under the front passenger carpet.
Fuse Card
There is also a fuse location card in the front fuse box to assist in locating various fuses.
Scheme 404
Main Fuse
The main fuse (F108) is located on the right hand side of the trunk, near the battery. F108 is a 200 amp fuse which feeds the front power distribution box. F108 supplies fuses F101 -107 as well as F35-F71.
Scheme 405
Electronics Carrier
The electronics carrier is located behind the glove box and contains various control modules and relay. Depending upon equipment levels and options, the carrier will contain different modules.
There are some modules and relays which will be present regardless of equipment, these include the General Module, fuel pump relay, horn relay, foglight relay and the blower relay for IHKA.
Scheme 406
Battery Safety Terminal
The E46 uses a trunk mounted battery which has a (B+) battery cable than runs the length of the vehicle. In the event of an accident, this cable could become compromised and there is a possibility of short circuit to the vehicle body. In order to reduce this possibility, the BST was added.
The BST is a pyrotechnic device which will disconnect the battery during an impact of sufficient severity. Although the main battery cable will be disconnected, the connection to the power distribution circuits will remain intact to allow other vehicle features to remain operational (power windows, locks etc).
Scheme 407
In comparison to the E36, the E46 was the first 3 series vehicle to make extensive use of bus networks. The E46 benefited from the latest bus technology which was introduced previously on the E38 and E39.
The E46 bus network consists of the following busses
- Diagnosis Bus (D-Bus)
- Controller Area Network (CAN Bus)
- Local Interconnect Network (LIN bus) (From 2003)
- M-Bus
- Body Bus (K-Bus)
Scheme 408
Diagnosis Bus (D-Bus)
The D-bus is used for diagnostic purposes, formerly referred to as TXD (RXD), this bus is used as an interface between the diagnostic equipment (DISPlus/Gt-1) and the various diagnosable systems.
The D-Bus is directly connected to certain modules for diagnosis, however some modules are diagnosed via a gateway. In the E46, the instrument cluster acts as a gateway between the D-Bus, CAN bus and K-Bus. For example, in order to read out fault codes from the LSZ, the instrument cluster provides the gateway between the K-Bus and D-bus.
From start of production, the E46 was equipped with a 20-pin underhood diagnostic connection as well as the required OBD II diagnostic connector (DLC). The OBD II connector provided communication with the ECM (DME) and the EGS control modules using aftermarket diagnostic equipment. To allow this communication, TXD II was added as an dedicated connection. TXD II is identical to the D-bus, but is connected only to pin 17 of the OBD II connector and the ECM. The EGS communicates via CAN.
In model year 2001, the 20-pin diagnostic connector was deleted. BMW diagnostic equipment now communicated exclusively through the 16-pin DLC.
Scheme 409
Body Bus (K-Bus)
The K-Bus is used for the majority of systems on the E46. It differs from the I/K structure used on the E38 and E39. The E46 does not use the I-Bus, but rather the K-Bus exclusively.
The K-bus is a single wire network throughout the vehicle. The K-bus voltage is approximately 12 volts.
Controller Area Network (CAN Bus)
The CAN bus is a two wire bus used to allow communication between powertrain related components and systems. The CAN network on the E46 uses a twisted pair configuration which also uses two terminal resistors of 120 ohms each for a total circuit resistance of 60 ohms.
M Bus
The M bus is used exclusively for the climate control system. The M bus allows the IHKA/R control module to communicate with the various stepper motors for temperature regulation and air flap control. There are 4 stepper motors used on the M-bus of the E46.
Local Interconnect Network (LIN Bus)
The LIN bus was not introduced on the E46 from start of production. The LIN bus was added to the E46 from 2003 for Adaptive Headlights (AHL) and for side view mirror control. The LIN bus consists of a single yellow/violet (GE/VI) wire.
