Fuse and Relay Diagram.

1989-1990: front supply distribution box

1991-1994: relays in the front power distribution box

The rear box is located under the rear couch, behind the driver’s seat. It contains the auxiliary fuses, relays and control modules.

1989-1990: rear power distribution box

1991-1992: rear power distribution box

Control box (Electronics box / E-box)

The electronic box is located in the near right hand corner of the driving direction, directly under the windshield. It is covered by a plastic cover with four screws. It is also cooled by an electric fan which rotates at low speed when the engine is running. If the temperature in the box exceeds 44 degrees Celsius, the fan starts spinning at higher speed.

In this box are the main control modules: engine, ABS, fuel system and electronic throttle (EML) if it is installed.

Additional Relay Units

The auxiliary relay box is located in the engine compartment on the left side of the vehicle, closer to the front. On later models, it also houses some fuses.

1989-1990: Additional Relay Box

1989-1990: Additional Relay Unit

Full List of Fuses

The difference between High and Low wiring

There are 2 types of wiring on the e34: the so called “High Version” and “Low Version”.

• The 518i, 520i and 524td have Low wiring.
• On the 525i-540i respectively High.

The wiring version can be determined by looking at the fuse block under the hood. If in the lower rows are large blocks of CCM (Check control module) and LKM (Light control module), it is the High Version, if there are the usual square relays – this version is Low.

The High Version has a self-diagnostic system, and the dashboard has a running line at the bottom. The Low version has neither.

In April 1989, the wiring and instrument panel layout was changed to be called Redesign – the Redesign Low Version dashboard was equipped with an electronic odometer with an LCD display instead of an electromechanical display, and the High Version dash layout underwent changes, which now also became known as Redesign. There is also some certainty that the wiring changes also took place when the M50 engines were upgraded for 1990.

It is believed that the High Version has wiring for all possible optional extras.

Now let’s move on to the fuse and relay boxes for each version.

Low Version Wiring

The fuses are located in the engine compartment on the left side and under the rear sofa. Let’s start with the engine compartment.

List of fuses in the wiring block (Low Version)

List of fuses under the rear seats (Low Version)

Relay in the mounting block (Low version)

Relay in the rear couch (Low version)

High Version Wiring

The fuses here are also located in the engine compartment on the left side and under the rear couch. Let’s start with the engine compartment.

List of fuses in the wiring block (High Version)

List of fuses under the rear couch (High Version)

Relay in the mounting block (High version)

Relay under the rear couch (High version)

How do I check the relay?

The easiest way to check the relay is to replace it with a known working relay. Relays are usually checked in this way at service stations. However, it is not always possible to quickly get the right relay at home, so we recommend the following way to check the so-called working relays, which include, for example, relays for the main and fog lights:

•  Remove the relay from the connector.
•  First check with a probe whether voltage is present at pin 30 of the relay’s connector. To do this, connect the tester to the ground and touch pin 30 of the connector with the tester lead. If there is voltage, the tester LED will illuminate. If the LED does not illuminate, find and repair the break in the circuit between the positive terminal of the battery and pin 30 of the relay connector.
•  Make a jumper from a piece of insulated wire by stripping the ends
•  Using the jumper fabricated, connect pin 30 of the relay connector (where the battery voltage is permanently present) to pin 87.
•  If the corresponding circuit closes when the jumper is installed (e.g. high beam comes on), then the corresponding relay is in good condition.
•  If the circuit does not close (e.g. the high beam still does not come on), find and repair the break in the circuit between pin 87 of the relay connector and the corresponding consumer.
•  If necessary, install a new relay

Original Fuse Code Numbers