General Model Information

Group 00
Maintenance and
General Hints

Bulletin Number
00 03 94 (2143)

Woodcliff Lake, NJ
June 1995
Product Engineering

SUBJECT:
E38 General Information

MODELS:
7 Series

General Information:
The new E38 replaces the E32 after a successful seven model year run. The E38 expands upon the E32's design philosophy and exhibits the best of BMW: luxury, elegance, and outstanding driving dynamics. The E38 is available in two body styles, standard and long wheelbase versions, and with two different engines (V8 and V12).

Design Objectives:
To develop an exclusive luxury vehicle, suited for long trips, with outstanding levels of comfort and refinement, driver oriented, exhibiting all the stylistic elements which trademark a BMW. Increased convenience of all system operation, particularly heating, ventilation and air conditioning. In addition maintain driver involvement via generous reserves of available power, superlative handling and suspension dynamics, and state of the art braking performance.

The following is a brief overview of the new E38 which illustrates some of the technology BMW employed in achieving the above goals.





Technical Specifications:

Powertrain:
The new 740i/iL are introduced with the familiar M60 B40 engine (4 liter, 8 cylinder, 32 valve). The new 750iL is introduced with the new M73 engine (5.4 liter, 12 cylinder, 24 valve). The M73 engine is based on the proven M70 engine. Please refer to TRI 11 01 95 (2146) for further details.

The A5S 560Z (5HP 30) automatic transmission is standard and includes an adaptive automatic transmission control system (AGS).

Please Note:
A converter clutch function (GWK) has been added to the adaptive transmission control system to improve fuel efficiency and occupant comfort. The GWK can only function properly if the new transmission fluid LT71141 is used. Should a repair be performed, this transmission fluid must always be used (BMW part number 83 22 9 407 807).





Bus Systems:

The use of multiplex communication technology. introduced with the E31, has been expanded and refined in the E38. The E38 contains six different bus systems:

1. K-Bus (Body Bus): Allows data to be exchanged between the IKE (instrument cluster electronic) and other body control modules: IHKA (heating and air conditioning control module), FBZV (remote control module) and GMIII (Basic Module).

2. M-Bus (Stepper Motor Bus): Allows communication between the IHKA and the various climate control system stepper motors.

3. D-Bus (Diagnosis Bus): Allows direct communication between the DIS tester and all control modules which are wired with the RxD and TxD lines, i.e., DME (digital motor electronics), AGS (adaptive transmission control), ZAE (central airbag control module), GRII (cruise control module) and IKE modules. The IKE also receives and transmits diagnostic messages from the DIS tester to the I-and K-Buses.

4. I-Bus (Information Bus): Is the communication line for all control modules which present system information to the driver, i.e., IKE, MID (multi-information display), MFL-CM (multifunction steering wheel), 0CM (check control module), LM (lamp module), Radio (DSP-digital sound processor), amplifier and cellular telephone.

5. P-Bus (Peripheral Bus): Allows communication between the GMIII and the following body control modules: PM-FT (driver's door module), PM-SB (driver's door switch block), PM-SHD (sunroof module) and PM-SM (seat memory module) and PM-BT (passenger's door module).





To save battery power, the GMIII is automatically switched to a sleep mode when the ignition is switched OFF and no functions are requested of it within 16 minutes. When the GMIII enters the sleep mode, it transmits a go to sleep signal to all P-Bus subscribers. The GMIII also controls a consumer cutoff function. Circuits controlled by this function will also be switched off as the GMIII enters the sleep mode. The following circuits are affected by the consumer cutoff function:

- map reading lights

- glovebox/trunk lights

- overload protection relay for the power seat and steering column motors

- transmission speed indicator lamp (Note: This results in the transmission speed indicator lamp remaining illuminated for 16 minutes after the ignition has been switched off.)

6. CAN-Bus (Controller Area Network Bus): Links the DME and AGS control modules. All driveline management systems are linked by way of this databus which exchanges the following crucial powertrain information:

- ignition on - engine speed
- engine load - road speed
- throttle angle - AC compressor state
- torque reduction signal - converter clutch lock-up status
- selected driving program - selector lever position
- speed stage in use - fuel cutoff (coasting)

Control Modules:
The following schematic illustrates the location of the 740i/iL's various control modules:





Please Note:
The following control modules must be coded prior to operation:

GRII DME AGS ABS/ASC+T CCM
GMIII LM IHKA ZAE IKE

Front Suspension:
The double-pivot front suspension with spring/damper struts, lateral control arms and leading link ensure outstanding road behavior, straight line stability and initial steering response.

The front axle subframe is of a cruciform pattern which provides superior rigidity and low weight. As in the E32, the subframe still acts as the mounting platform for the engine mounts and steering box. All mating components attach directly to the subframe eliminating the need for a wheel alignment should the subframe need to be lowered for repair.

The only adjustment to the front suspension is the toe-in angle:

Total Toe = 0.234° +/- 0.083°

The front suspension's lateral control arms are aluminum forgings. The leading links are steel and have large volume, hydraulically dampened rubber mounts. This results in precisely controlled suspension movement and maximum insensitivity to front axle vibration (wheel imbalance).

The front coil springs are variable diameter which still allow precise spring calibration yet allow a lower front end profile and a more sloped hood. Twin tube shock absorbers ensure low noise, optimal response and vibration free operation





Rear Suspension:
The E38 is equipped with an all new-patented multi-link rear suspension. It is similar in concept to the five link system introduced with the E31, though more compact.

The rear axle subframe is secured to the body by four large rubber bushings. The bushings permit some controlled movement and also minimize noise transmission. As before, the rear differential is mounted to the subframe with rubber dampers, further reducing interior noise and vibration.

The camber and toe are adjustable. The specifications are:

Total Toe = 0.234° +/- 0.083°
Camber = -0.217° +/- 0.050°

Wheels, Tires, Brakes:
The new E38 models are equipped with 16 inch wheels which allow the new 7 Series to have brakes of increased performance.





A new foot operated parking brake has been introduced with the E38. The pedal operates dual-servo drums of 180 mm diameter on the rear axle. The parking brake system incorporates automatic wire cable equalization, ensuring uniform left/right braking force distribution.

The ABS 5/ASC+T (optional) systems introduced on the 1994 E34 models are carried over to the E38. For further details please refer to TRI 34 01 94 (2142).

The only change to the ABS system is the wheel speed sensor. The E38 now uses Hall effect sensors instead of the induction pulse sensors used on the E34. This results in several advantages: the Hall effect sensors emit a digital signal which can be directly processed by the control module. The sensor is also immune to induced voltage spikes and the voltages generated do not increase with increasing road speed.

Body:
The new E38 offers outstanding ride comfort, road behavior and safety performance. This was achieved by increasing the body's static and dynamic rigidity. The peak values achieved are 100% higher than the excellent values reached by the E32.

The windshield and rear windows are bonded in and almost completely flush with their mating body panels. The roof pillar cross sections have been further reduced to improve outward visibility.

The entire body has excellent corrosion resistance thanks to the extensive use of galvanized sheet metal. In fact, in critical areas, both sides of the sheet metal are galvanized.

The hood is rear hinged with integral kidney shaped grills. The slope of the hood is increased towards the windshield to conceal the windshield wipers. Two gas charged struts ease the opening of the hood. The hood is secured by two rotary-striker catches and one trap hook Four pivot point hinges allow an opening angle of over 45° in the normal position and up to 80° in the workshop position.

The trunk lid incorporates a restrained spoiler lip. Four point hinges are used to allow an opening angle of 90°. The luggage compartment sill has been lowered in comparison to the E32. An automatic soft close feature is standard.

Door warning lights are illuminated after a door has been opened. The door outside handles are painted in body color. Access to the interior has been enhanced by larger door cutouts and a door opening angle of 68°.

A new anti-trap prevention system is introduced with the E38. A pressure sensitive strip is located at the top of each door's window frame. If the strips are pressed with sufficient force, the closing window will immediately reverse directions, as with earlier systems. This results in anti-trap protection for the full range of window travel.

Locks:
The E38 has only one external door lock, located in the driver's door, which can lock and unlock all four doors. The door lock has a free-wheeling function. If any key other than the vehicle key, or tool, is inserted into the lock cylinder the cylinder will free-wheel. Opening the lock via force is thus impossible.

The ignition lock has an internal rib which will break if excessive torque is applied (5 to 7 Nm), via a tool or incorrect key, during an attempt to force the lock. The cylinder will then free-wheel. In such cases the complete steering lock and lock barrel must be replaced.





Supplemental Restraint Systems:
Driver and front passenger airbags are standard as well as pyrotechnic seatbelt tensioners. Depending on the severity and angle of a frontal impact, both seatbelt pyrotechnic tensioners and the airbags are triggered in two different precisely coordinated steps. The front passenger seat has pressure sensors integrated into it to prevent the passenger side airbag from deploying if the seat is not occupied. The front seatbelt catches have contacts which will confirm that the seatbelts are in use and only then can the belt pre-tensioners be deployed.

Please refer to TRI 72 01 93 (2137) for further details regarding the ZAE system.





A new side impact system is incorporated into all doors. The doors contain aluminum reinforcement braces. The lower ends of the braces have a metal hook bolted to them. In the event of a severe side impact, the hook(s) will grab a notch in the B-pillar or rear quarter, hindering door intrusion into the passenger compartment.

Electronics:
The E38's electronic systems provide many more functions than were available on the E32. These include: fine control of the intermittent wipe interval via a thumb wheel, selective door and trunk lid release, and one touch opening for all windows. In general, a higher standard of electrical system reliability was achieved by the replacement of many mechanical relays and switches with semiconductor technology.

New systems were developed to enhance driver and occupant comfort and convenience, including a new generation of cruise control and temperature controlled seat heating.

The control of the vehicle's lighting system has been greatly simplified by the use of improved software. The bulb switching, bulb monitoring, indicators and instrument lighting have all been combined into a single control unit (LM). The brake light switch is now completely silent involving no mechanical contact. LEDs are exclusively used for instrument and control illumination to eliminate the need for bulb replacement.

The total amount of wiring necessary has been greatly reduced by the systematic use of multiplexing technology and component integration. To reduce the number of different versions of control modules required, extensive encoding takes place during vehicle production at the factory and is required every time such modules need to be replaced.





If the car's electrical system becomes overloaded, the battery voltage could drop too low (particularly at low engine speeds), certain systems without safety relevance (i.e., heated rear windows, heated seats) are temporarily shut down after a minimum voltage threshold has been reached. The systems which have been shut down are reactivated as soon as the appropriate voltage is again achieved.

BMW's trademark twin circular headlamps, one for high beam and one for low, are retained. Both are mounted behind a common integral clear glass cover as introduced on the E36.

Audio Communication Systems:
The design goal of reducing the number of control and displays visible to the driver has been achieved by grouping related functions together in a single unit. The multifunction display (MID) integrates and displays the audio, telephone, clock, and on-board computer controls. This results in a substantial reduction in the total number of keys and displays:

The following functions are controlled or displayed in the MID:

Clock Functions Radio/CD/Cassette On-Board Computer

- actual time - radio station - average speed
- date - memory channels - refueling range
- MEMO reminder - Dolby(R) B/C - distance remaining
- timer/stopwatch - speed dependent volume - average fuel consumption
- set speed limit warning
- theft proofing CODE

Two audio systems are available:
Standard and Premium Sound System. The standard system has two tweeters, two mid-range and two bass speakers in the front doors and two tweeter and two bass speakers in the rear doors. The standard amplifiers are equalized to suit specific models and include active frequency crossovers. Total available power is 10 x 15 Watts at 1% total harmonic distortion (THD).

The Premium Sound System has the above speakers, with even higher performance, in the same locations and in addition a tour sub-woofer speaker system is located under the rear window shelf. This system has the following additional features:

- speed dependent volume
- volume dependent equalization
- spatial simulation (room size and reverberation)
- dynamic compression
- tweeter output stages, 4 x 15W @ 1% THD
- mid-range output stages, 2 x 15W @ 1% THD
- woofer output stages, 4 x 28W @ 1% THD
- subwoofer output stages, 4 x 15W @ 1% THD





Multifunction Steering Wheel:
The E38's steering wheel now has controls for some of the audio and telephone system functions integrated into the pad. Radio stations, CD/cassette tracks and volume settings can be directed with the steering wheel control buttons. Cruise control functions are also controlled: accelerate/decelerate, resume and cancel. The air conditioning system's Air Recirculation function can also be directed from the steering wheel.





Heating, Ventilation and Air Conditioning:
All E38 models are equipped with a more sophisticated IHKA system.

The IHKA controls contain the following new features:

- all IHKA control electronics are integrated into the control panel
- new control software is used to regulate ventilation and air temperature
- drivers and passenger's temperature displays
- separate air volume and blower speed controls for both driver and front passenger

Intake air passes through two activated charcoal microfilters which are integrated
into the hood. The climate control system blowers are located within the passenger
compartment.





Please Note:
Never operate an E38 without the microfilters installed. There is the danger of water being drawn into the heater and/or damage to the electrical system.

Both fresh and recirculated air are continuously filtered through the microfilters. This in conjunction with the recirculated air control (AUC) results in greatly improved interior air quality.

The engine's residual heat can also be used to keep the interior's air warm for up to 16 minutes after shutting down the engine. Unpleasant air currents are also kept to a minimum by providing effective back-pressure compensation over the E38's entire speed range.

In addition to the separate air volume controls to either side of the passenger compartment, individual control of the air flow distribution is possible via the manual program keys.

Inspection and Maintenance:
Please be aware that there have been several changes to the E38's maintenance schedule in comparison to the E32's. For example:

Quality Certification I Does not apply

Inspection I Replace alarm remote battery in all master keys (refer to
SI 00 09 94 [4004]). The engine coolant replacement
interval has been increased to every 3 years.

Inspection II The rear axle synthetic oil change interval has been
increased to every second Inspection II (refer to SI 33 01
92 [3667]). It is no longer necessary to check the
condition of all drive belts.

For further details regarding new vehicle preparation and maintenance requirements, please refer to SI 00 05 93 (3769).