Positioning:
The BMW 850i (E31) was a flagship luxury grand tourer, representing BMW's pinnacle of automotive engineering and design in the early 1990s.
Competitors:
Competed with high-end coupes such as the Mercedes-Benz SEC, Porsche 928, and Jaguar XJS.
Design:
Striking 'shark nose' styling, pop-up headlights, pillarless hardtop coupe design.
Powertrain:
Initially featured the V12 engine, a testament to BMW's engineering prowess.
Technology:
Advanced for its time, including electronic throttle control, self-leveling headlights, and sophisticated onboard diagnostics.
Utility:
This wiring diagram manual is indispensable for owners and technicians working on the complex electrical systems of the 1991 BMW 850i E31.
Target Audience:
Enthusiasts, vintage BMW specialists, and independent repair shops.
Engine Management:
Full wiring for DME (Digital Motor Electronics), ignition, fuel injection, sensors, actuators.
Powertrain Control:
Wiring for transmission control (e.g., automatic transmission control unit), shift interlocks.
Chassis Electrical:
Wiring for lighting (headlights, taillights, interior), wipers, washers, horn, power windows, mirrors, locks.
Comfort And Convenience:
Wiring for climate control (HVAC), power seats, heated seats, sunroof, central locking, cruise control.
Instrumentation:
Wiring for instrument cluster (speedometer, tachometer, fuel gauge, temperature gauge), warning lights, OBC (On-Board Computer).
Audio And Navigation:
Wiring for radio, speakers, antenna, and early navigation systems if applicable.
ABS:
Wiring for ABS (Anti-lock Braking System) control unit and sensors.
Airbags:
Wiring for airbag system components (control unit, sensors,SRS warning light).
Troubleshooting:
Diagnostic routing for electrical faults, component identification.
Component Location:
Diagrams indicating the location of electrical components and connectors.
Connector Pinouts:
Detailed pin assignments for various electrical connectors.
Fuse And Relay Identification:
Identification and location of fuses and relays within the vehicle's electrical system.
Level Of Detail:
Comprehensive, factory-level detail suitable for professional diagnostics and repairs.
Diagnostic Aid:
Essential for tracing electrical circuits, identifying shorts, open circuits, and ground faults.
Transmission Type:
4-speed Automatic (ZF 4HP-24)
Transmission Type:
6-speed Manual (Getrag 630G)
Adaptive Control:
Automatic transmission featured adaptive shift logic.
Automatic Transmission Fluid:
Dexron III or equivalent (e.g., ZF TE-ML 04D, 14A)
Automatic Transmission Capacity:
Approximately 7.5 Liters (15.8 US quarts) for a complete refill.
NHTSA Crash Test:
Data not readily available for this era's specific crash test rating format.
ABS:
Standard Anti-lock Braking System (ABS).
Traction Control:
Optional ASC (Automatic Stability Control) available on some models.
Airbags:
Driver and passenger airbags (SRS - Supplemental Restraint System) standard.
Seatbelts:
3-point inertia-reel seat belts with pretensioners.
Audio System:
BMW Bavaria C Business RDS or similar high-fidelity sound systems.
Cruise Control:
Electronic cruise control.
Onboard Computer:
BMW On-Board Computer (OBC) providing various vehicle status and trip information.
Early Systems:
While rudimentary by modern standards, early forms of vehicle network communication and diagnostics were present, relying on specific wiring pathways.
Oil Change:
Typically every 7,500 - 10,000 miles (12,000 - 16,000 km) or annually, depending on usage and oil type, as indicated by the vehicle's oil service indicator.
Major Service Items:
Spark plugs (every 60,000 miles), coolant flush (every 2-3 years), transmission fluid and filter service (per manual recommendations, often around 60,000 miles).
Engine Oil:
SAE 5W-30 or 5W-40 synthetic oil meeting BMW Longlife-98 specification or equivalent.
Engine Oil Capacity:
7.5 Liters (7.9 US Quarts)
Brake Fluid:
DOT 4 Low Viscosity (LV) or DOT 5.1
Electrical Gremlins:
Due to the complexity and age, electrical issues are common. This manual is crucial for diagnosing them. Common areas include wiring harness degradation, ECU failures, and sensor faults.
Cooling System:
Plastic components in the cooling system can become brittle over time. Regular inspection and replacement are recommended.
Suspension:
Self-leveling rear suspension components can wear; regular checks are advised.
V12 Specifics:
The M70 engine's complexity, including its dual VANOS (variable valve timing), dual ignition coils, and dual ECUs, requires specialized knowledge and tools, making detailed wiring diagrams essential.
Bmw Legacy:
BMW has a long history of producing driver-focused, technologically advanced vehicles, often pushing the boundaries of automotive engineering.
E31 Development:
Developed as BMW's flagship coupe, intended to compete with established luxury GTs and showcase new technologies. It was a clean-sheet design, unrelated to previous BMW coupe lines.
Production Years:
1990-1999
Manufacturing Location:
Dingolfing Plant, Germany
Total Units Produced:
30,618 (across all E31 variants)
850I Units Produced:
Approximately 16,941
