BMW X5: Troubleshooting

CONTENTS OF ENGINE ELECTRICAL SYSTEM GENERAL

General Information -> Working on ignition system.

-> Removing and installing electronic control units.

-> Welding work (overload protection of control units).

-> Disconnecting and connecting battery.

-> External jump-starting aid.

INSTRUCTIONS FOR DISCONNECTING AND CONNECTING BATTERY

Observe safety instructions for handling vehicle battery.

Before disconnecting battery:

Turn off the ignition and other electrical loads/consumers to prevent sparking when reconnecting.

NOTE: If the ignition is not turned off when the battery is disconnected, fault memories may be set in some control units.

IMPORTANT:

• There is a danger of mixing up battery leads: If the battery positive and negative leads are the same color and you are in doubt, follow the polarity to the battery, then mark and cover the leads.
• On vehicles with radio code: After disconnecting the battery, the radio code must be re-entered. Therefore obtain the radio code card from the customer beforehand. Note stored stations and restore them after connecting the battery.
• Stored settings of the on-board computer and clock will also be lost.
• All available central keys must be recoded for cars with first generation infrared transmitter locking systems.

General notes on disconnecting battery:

• Do not disconnect battery leads and leads from alternator and starter motor while engine is running.
• Cars with IBS on battery negative terminal:
  Do not under any circumstances pull/lever off pole shoes by force.

  Do not under any circumstances release socket-head cap screw of IBS.

• Detach terminal of battery negative lead from car battery and second battery if fitted. Cover battery negative terminal(s) and secure.
• When work is carried out on the electrical system, faults may be caused in the fault memories of some control units when the battery is connected.
• When installing battery terminal: Tightening torque 61 21 1AZ.

After connecting battery:

IMPORTANT: The scope of application of some systems may be restricted after a power supply interruption. Likewise, individual settings may be lost.

Example:

• Vehicles with automatic engine start-stop system (MSA): MSA function is active only after learning period (vehicle must not be woken for a period of 6 hours) > if necessary, notify customer of the situation.
• E46 (AWD)/ E53/ E83: Carry out steering angle sensor adjustment.
• If necessary, carry out adjustment of active front steering.
• If necessary, activate sliding sunroof.
• If necessary, activate power windows.
• If necessary, activate mirror with compass.

Please refer to the Program user documentation for further information on vehicle-specific activation.

Vehicles with a two-battery system

Starter and equipment batteries

A two-battery system has a starter battery circuit and an equipment battery circuit. A secondary control unit monitors both battery circuits. Depending on the situation, the battery circuits are connected to or isolated from the secondary control unit via an isolating relay.

Two AGM batteries, whose design and properties are described in AGM batterie are used as a storage battery.

IMPORTANT: These batteries must not under any circumstances be charged with a voltage in excess of 14.8 V. Rapid programs must not be used either.

Receiving/giving starting assistance via jump start terminal

The engine can be jump-started with an external voltage supply via the jump start terminal on the right side of the engine compartment.

NOTE: The starter battery is isolated from the alternators when the engine hood/bonnet is open.

Giving starting assistance via the jump start terminal is thus limited by the capacity of the starter battery when the engine hood/bonnet is open.

Charging starter and equipment batteries via jump start terminal

The starter battery is charged as a matter of priority with a charger connected to the jump start terminal. The voltage at the starter battery is the decisive factor in determining whether the equipment battery is also included in the charging operation. The secondary control unit automatically detects a charging operation at a charging voltage at the starter battery of > or = 13.5 V. The isolating relay is closed and thus the equipment battery is connected in parallel. Both batteries are now charged.

Prerequisite:

• Terminal 61 inactive
• Terminal 15 inactive

If terminal 15 becomes "active" during the charging operation, the isolating relay is opened immediately and again only the starter battery is charged.

NOTE: When the engine hood is open, the isolating relay is also opened in normal operation when the engine is running.

This mode is automatically reset once a distance of 5 km has been driven.

Trickle charging

The increased closed-circuit current consumption can be compensated for via the jump-start connection point with the aid of the "Acctiva easy" battery trickle charger.

INSTRUCTIONS FOR REMOVING AND INSTALLING ELECTRONIC CONTROL UNITS

IMPORTANT:

• Disconnecting the vehicle battery will cancel the fault memories of control units. Consequently, before disconnecting the car's battery, always interrogate the fault memories. Investigate stored faults and, once any faults have been remedied, cancel the fault memory.
• Control unit plugs should only ever be connected and disconnected while the ignition is turned off.
• The removal and installation of components, relays, fuses etc. can cause faults to be stored in fault memories capable of self diagnosis. Always interrogate the fault memories after completing work on the electrical system.
• Investigate stored faults and, once any faults have been remedied, cancel the fault memory.

Comply with the following when replacing the DME/DDE (Digital Motor Electronics/Digital Diesel Electronics):

• Always read out hardware/software version of the corresponding control unit with DIS tester.

  Comply with the instructions of the DIS tester on the steps coding and programming.

  On vehicles with electronic vehicle immobilization, comply with the instructions of the DIS tester.

• Each control unit is programmed with certain basic values, which serve as mean values. The control unit receives different input values, depending on engine condition, which are compared with the stored values. The adaptive system compares the input values with the stored map values. The control commands are routed to the relevant actuators.
• If, for example, the DME control unit would be without current for a long time (more than an hour), its adaptive system would lose the stored values. When a cleared control unit is restarted or a new control unit is installed, the adaptive system must read in and store the input values of the associated engine as new basic values itself.
• This procedure could lead to erratic idling and disturbed overrunning of the engine after starting.

  Depending on the engine it could require some time before all values are adapted to the engine condition.

• Therefore observe the following procedure before replacing or reinstalling a DME/DDE control unit:
  1. If possible before exchanging control unit, run engine up to operating temperature.
  2. Remove the control unit, install a new control unit and operate vehicle at different engine speeds.

NOTES ON CHECKING IGNITION SYSTEM

-> Spark plug faults

-> Ignition coil faults

-> Further fault patterns with evaluation

-> Additional fault notes for troubleshooting

Oscillograms -> Normal oscillogram

-> Oscillograms of ignition coils from different manufacturers

Check -> Secondary signal for stationary ignition distribution

READ NEXT: