🏷️ Basic Information

Make:

Mitsubishi

Model:

Sigma Diamante

Body Style:

Full-size Sedan

Generation Name:

Third Generation (1990-1996)

Chassis Codes:

F15A, F17A, F25A, F27A, F31A, F36A

Engine Codes:

6G72, 6G73, 6G74

👋 Introduction

Segment:

Full-size Luxury Sedan / Executive Car

Target Audience:

Discerning buyers seeking comfort, performance, and advanced features for their daily commute and long-distance travel.

Key Competitors:

Toyota Camry, Honda Accord, Nissan Maxima, Ford Taurus, Chevrolet Lumina, BMW 3-Series, Mercedes-Benz C-Class (depending on specific market and trim).

Distinguishing Elements:

Sophisticated styling, V6 engine options, available all-wheel drive, premium interior appointments, and a focus on a quiet and comfortable ride.

Manual Value Proposition:

Empowers owners and technicians with the in-depth knowledge required for accurate diagnosis, efficient repair, and proper maintenance, preserving the vehicle's luxury and performance.

📋 Manual Details

Covered Years:

1990, 1991, 1992, 1993, 1994, 1995

Estimated Page Count:

Approximately 1500-2000 pages (typical for comprehensive workshop manuals of this era)

Type:

Workshop Service and Repair Manual

Language:

English

Format:

Digital (PDF) - assumed for modern sales, but original was likely print

📖 Manual Coverage

Engine:

Engine mechanical (assembly, disassembly, timing, lubrication, cooling), fuel system (injection, pumps, injectors), ignition system, emission control systems.

Transmission:

Automatic transmission (AT) and Manual transmission (MT) repair, overhaul, torque converter, valve body diagnostics, fluid specifications.

Drivetrain:

Front-wheel drive (FWD), All-wheel drive (AWD) systems (if applicable), differentials, driveshafts, CV joints, propeller shaft, rear differential (for AWD).

Suspension:

Front and rear suspension systems, shock absorbers, struts, springs, control arms, bushings, alignment specifications.

Brakes:

Hydraulic brake system, ABS (Anti-lock Braking System), disc brakes (front and rear), brake pads, rotors, calipers, master cylinder, brake fluid specifications.

Steering:

Power steering system, steering gear, steering column, tie rods, power steering fluid.

Electrical:

12V electrical system, battery, alternator, starter motor, wiring diagrams, fuses, relays, lighting systems, instrument cluster, power accessories.

Climate Control:

Heating, Ventilation, and Air Conditioning (HVAC) system components, refrigerant, operation, diagnostics.

Body:

Body panel removal and installation, doors, hood, trunk, interior trim, glass replacement, door locks, body repair procedures.

Safety Systems:

Seat belts, airbag system (SRS) components and removal/installation procedures (with strict safety warnings).

Maintenance:

Routine maintenance procedures: oil changes, filter replacements, spark plug replacement, fluid level checks and top-offs, belt inspections and replacement, tire rotation.

Diagnostics:

Troubleshooting guides, symptom-based diagnostics, fault code interpretation (OBD-I era), diagnostic connector locations.

Repair:

Step-by-step repair procedures for all major mechanical and electrical components, including complete engine and transmission overhauls.

Overhaul:

Detailed instructions for engine and transmission rebuilding, including specifications for clearances, torques, and component wear limits.

Installation:

Procedures for installing new or replacement parts, including torque specifications and critical alignment requirements.

Depth:

Comprehensive: Covers everything from basic maintenance to complete engine and transmission rebuilds, electrical system diagnostics, and bodywork.

Diagnostic Capability:

Advanced: Includes diagnostic charts, trouble codes, and detailed explanations of system operation to facilitate problem-solving.

📊 Manual Specifications

Digital Format:

PDF (searchable text, bookmark support, printable pages recommended)

Image Resolution:

High resolution for clear diagrams and schematics.

Original Binding:

Perfect bound or coil bound (typical for OEM service manuals)

Original Paper:

Durable, high-quality paper suitable for workshop environments

⚙️ Engine Specifications

Engine 1 Name:

6G72 V6

Engine 1 Displacement:

3.0 Liters (2972 cc)

Engine 1 Configuration:

V6 SOHC (Single Overhead Cam) or DOHC (Double Overhead Cam)

Engine 1 Horsepower:

Approx. 150-170 HP (SOHC), 195-210 HP (DOHC - ECI Multi)

Engine 1 Torque:

Approx. 170-190 lb-ft (SOHC), 200-220 lb-ft (DOHC)

Engine 2 Name:

6G73 V6

Engine 2 Displacement:

2.5 Liters (2497 cc)

Engine 2 Configuration:

V6 SOHC

Engine 2 Horsepower:

Approx. 130-145 HP

Engine 2 Torque:

Approx. 150-165 lb-ft

Engine 3 Name:

6G74 V6 (JDM/specific markets)

Engine 3 Displacement:

3.5 Liters (3497 cc)

Engine 3 Configuration:

V6 DOHC (ECI Multi)

Engine 3 Horsepower:

Approx. 230-240 HP

Engine 3 Torque:

Approx. 225-235 lb-ft

Fuel Delivery:

Multi-point Fuel Injection (MPFI) / ECI Multi

Fuel Type:

Unleaded Gasoline

Ignition System:

Electronic Ignition (Distributor-less or Distributor-based depending on year/market)

🔧 Transmission

Transmission Type:

4-speed Automatic Transmission (F4A51, V4A51)

Transmission Type:

5-speed Manual Transmission (available on some trims/markets)

AWD System:

Electronic All-Wheel Drive (E-AWDi) with viscous coupling center differential on certain models (e.g., GDI Sport)

At Features:

Sportronic (sequential shifting capability on later models), electronically controlled shifts.

📐 Dimensions

Length:

Approx. 4,965 mm (195.5 in)

Width:

Approx. 1,770 mm (69.7 in)

Height:

Approx. 1,400 mm (55.1 in)

Wheelbase:

Approx. 2,750 mm (108.3 in)

Curb Weight:

Approx. 1,500 - 1,700 kg (3,300 - 3,750 lbs) depending on engine and configuration

Gross Vehicle Weight Rating:

Typically around 2,000 kg (4,400 lbs)

🛡️ Safety Features

NHTSA Ratings:

NHTSA crash test data for this era is limited and varied by market. Generally considered a safe vehicle for its time.

ABS:

Standard or optional Anti-lock Braking System (ABS) on most models.

Traction Control:

Optional Traction Control System (TCS) on some higher trims.

Airbags:

Driver and front passenger airbags standard on most later models, potentially optional on earlier ones.

Seat Belts:

3-point seat belts with pretensioners for front occupants.

Body Structure:

Reinforced safety cell, crumple zones.

💡 Technology Features

Audio System:

Premium audio systems with cassette player, AM/FM radio, often with CD player option. Speaker count and quality varied by trim.

Climate Control Tech:

Automatic climate control with digital display on higher trims.

Cruise Control:

Standard cruise control on most models.

Phone Integration:

Limited to early hands-free kits or aftermarket installations; no integrated Bluetooth or smartphone connectivity.

🔧 Maintenance

Oil Change Interval:

Every 5,000-7,500 miles (8,000-12,000 km) or 6 months, whichever comes first. Consult manual for specific grade.

Timing Belt Replacement:

Recommended every 60,000-100,000 miles (96,000-160,000 km) or 5-7 years. Critical for interference engines (like V6 DOHC).

Spark Plug Replacement:

Typically every 30,000-60,000 miles (48,000-96,000 km), depending on plug type (copper, platinum, iridium).

Coolant Replacement:

Every 2-3 years or 30,000-50,000 miles (48,000-80,000 km).

Engine Oil:

API SG or higher, SAE 10W-30 or 10W-40 recommended. Check manual for exact viscosity by temperature.

Transmission Fluid At:

Mitsubishi DiaQueen ATF-SP II M or equivalent Dexron III/Mercon compatible fluid.

Brake Fluid:

DOT 3 or DOT 4 brake fluid.

Power Steering Fluid:

ATF Dexron II or equivalent power steering fluid.

Engine Misfires:

Common due to aging ignition coils, spark plug wires, and fuel injectors.

Transmission Harsh Shifting:

Can be related to low fluid, clogged filter, or worn valve body components in the automatic transmission.

Suspension Wear:

Worn control arm bushings, ball joints, and sway bar links can lead to clunking noises and poor handling.

Electrical Gremlins:

Age-related issues with wiring harnesses, grounds, and sensor failures can cause intermittent problems.

Radiator Leaks:

Aging plastic tanks on radiators can develop cracks and leaks.

📚 Vehicle History

Mitsubishi Automotive:

Mitsubishi Motors Corporation, a part of the Mitsubishi Group, has a long history of automotive manufacturing known for robust engineering and innovative technologies, particularly in engines and four-wheel-drive systems.

Sigma Lineage:

The Sigma nameplate has been used by Mitsubishi for various models, with the Diamante serving as its flagship sedan in many global markets during this period. It was based on the Mitsubishi 'Sigma' platform, sharing components with vehicles like the Mitsubishi 3000GT/GTO.

Diamante Purpose:

Positioned as a premium, large sedan, the Diamante aimed to compete with established luxury marques, offering a blend of performance, comfort, and advanced technology.

Manufacturing Location:

Primarily manufactured in Japan.

Production Years Global:

1990-2005 (across generations and market name variations)

🏆 Awards & Recognition

Car And Driver Awards:

The Diamante was often listed on Car and Driver's '10Best' list in previous generations and was well-regarded for its value and features in its class.

Consumer Reports Ratings:

Ratings varied by year and specific model, but generally positioned as a competitive offering with good value, though some reliability concerns were noted in certain areas.

Iso Certification:

Mitsubishi Motors Corporation adheres to ISO 9001 and ISO 14001 standards for quality and environmental management.