BMW 3 Series Service Manual (E39)

Two common causes of driveability problems are incorrect system voltage and bad grounds.

System voltage

Digital motor electronics (DME) requires that the system (battery) voltage be maintained within a narrow range of DC voltage. DC voltage levels beyond or below the operating range, or any AIC voltage in the electrical system 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. An undercharged battery can amplify AIC alternator output ripple.

To make a quick check of the battery charge, measure the voltage across the battery terminals with all cables attached and the ignition off. Afully charged battery will measure 12.6 volts or slightly more, compared to 12.15 volts for a battery with a 25% charge.

The DME system operates at low voltage and current levels, making it sensitive to small increases in resistance. The electrical system is routinely subjected to corrosion, vibration and wear, so faults or corrosion in the wiring harness and connectors are not uncommon. Check the battery terminals forcorrosion or loose cable connections. See 121 Battery, Starter, Alternator for additional information.

If a battery cable connection has no v~siblefaults but is still suspect, measure the voltage drop across the connection. A large drop indicates excessive resistance, meaning that the connection is corroded, dirty, or damaged. Clean or repairthe connection and retest.

NOTE-

For instructions on conducting a voltage drop test and other general electrical troubleshooting information, see 600 Electrical System-General.

Visually inspect all wiring, connectors, switches and fuses in the system. Loose or damaged connectors can cause intermittent problems, especially the small terminals in the ECM connectors. Disconnect the wiring harness connectors to check for corrosion, and use electrical cleaning spray to remove contaminants.

Main grounds

Good grounds are critical to proper DME operation. If a ground connection has no visible faults but is still suspect. measure the voltage drop across the connection. A large voltage drop means high resistance. Clean or repair the connection and retest.

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110-3

Engine Removal and lnstallationl

Q Fuel line plugs

(Tool No. BMW 13 5 281 / 13 5 282)

4 Fuel line removal tool (Tool No. BMW 16 1 050)

CAUTION-

Disconnectingthe battery may erasefault code@)storedin memoiy Check for fault codes prior to disconnecting the battery cables.

If the MIL (Malfunction Indicator Light, also may be called "Check Engine" or "ServiceEngine Soon" light) is illuminated, see OBD On-Board Diagnostics for DME fault code information.

It orhersysrem faults have been detected,as indicated I by an ~llum~natedABS, SRS orASC/DSC ~ a r n i n light, see the appropriate repair group in this manual or an authorized BMW dealer for more information on fault codes.

NOTE-

Engine removal procedures are similar for all 6-cylinder models. When differences exist, they are noted at the beginning of each step. Engine are referred to by engine code. See 100 Engine-General for engine code and application information.

@Be sure to cover all painted surfaces before beginning the removal procedure. As an aid to installation, label all components, wires and hoses before removing them. Do not reuse gaskets, O-rings or seals during reassembly.

The intake manifold must be removed on &cylinder models before the engine can be removed.

WARNING-

Due to risk of personal injury, be sure the engine is cold before beginning the removal procedure.

110-4

/Engine Removal and Installation

4 Remove left and right interior ventilation ducts (lefl side shown):

Release ventilation filter cover latch (A) and remove cover.

Release plastic loclting tab (6) or release locking tabs on top of duct (later models).

Rotate duct counterclocltwise to unloclt from bulkhead and remove (arrow).

Disconnect electrical harness from hood switch (C).

Release spring loclt (D).

Slide filter housing away from inner fender to remove.

Removal of right side ventilation duct is similar.

Remove rear bulkhead panel:

-Remove rubber sealing gasket (arrow). Remove 3 mounting clips (A).

Remove 4 retaining screws (6). Lift off panel.

Remove complete air filter housing:

Loosen intalte duct hose clamp (A) at throttle assembly.

Loosen clamp and remove idle control line from intalte duct

(6) and (where applicable) disconnect idle speed control valve electrical harness connector.

Disconnect harness connector (C) from mass air flow sensor.

Remove air filter housing mounting screw (D).

Disconnect vent tube (E).

Loosen air intake duct clamp (F).

Carefully lift air filter housing out of engine bay.

4 Disconnect fuel lines by sliding locking collar in (arrows)and pulling line apart.