🏷️ Basic Information

Make:

Subaru

Model:

Impreza WRX STI

Model Code:

GDB (Hatchback/Wagon), GGB (Sedan - for some markets, but typically GDB refers to the chassis for this generation)

Model Generation:

Third Generation (2002-2007, chassis code GDB/GGB), specifically covering the mid-cycle refresh

Chassis Code:

GDB

👋 Introduction

Positioning:

The 2004-2005 Impreza WRX STI represents a pinnacle of rally-inspired performance in a production sedan, targeting enthusiasts and drivers seeking track-capable handling and potent turbocharged power.

Competitors:

Competed against performance variants of models like the Mitsubishi Lancer Evolution, Ford Focus RS, Volkswagen Golf R, and Audi S3 of the era.

Performance Focus:

Renowned for its symmetrical All-Wheel Drive system, turbocharged Boxer engine, and track-tuned suspension, offering exceptional grip and acceleration.

Rally Heritage:

Directly derived from Subaru's World Rally Championship (WRC) heritage, carrying the performance DNA of its motorsport counterparts.

Value Proposition:

Provides official, dealer-level repair and maintenance information, empowering owners and independent shops to perform accurate and efficient servicing.

📋 Manual Details

Covered Years:

2004, 2005

Region Of Origin:

Likely North American market based on WRX STI designation, but often includes global specifications.

Estimated Page Count:

1500+ (Typical for comprehensive factory service manuals)

Type:

Factory Service Manual (FSM) / Workshop Manual

Language:

English

Format:

Digital Download (PDF likely)

📖 Manual Coverage

Engine:

2.5L Turbocharged EJ257 Boxer Engine (including timing, lubrication, cooling, fuel injection, ignition, emissions, and engine management)

Transmission:

6-speed Manual Transmission (TZ1A3ZG6KA, TY757VW4AA, etc. - specific gearboxes may vary by market and trim)

Drivetrain:

All-Wheel Drive System (DCCD - Driver's Control Center Differential, center differential, front/rear differentials, driveshafts, axles)

Suspension:

Front MacPherson strut with lower control arm, Rear multi-link suspension, adjustable components (camber bolts, etc.)

Brakes:

Front 4-piston Brembo calipers with 325mm ventilated discs, Rear 2-piston Brembo calipers with 300mm ventilated discs, ABS, Brake booster, master cylinder

Steering:

Power-assisted rack and pinion steering system

Electrical:

Complete electrical schematics, Body Control Module (BCM), ECU, sensors, lighting, power windows, mirrors, HVAC controls, audio system, airbags

Body And Trim:

Exterior body panels, interior trim, bumpers, spoilers, doors, hood, trunk, glass

HVAC:

Heating, Ventilation, and Air Conditioning system operation and repair

Fuel System:

Fuel tank, fuel pump, fuel lines, fuel injectors, fuel pressure regulator

Exhaust System:

Manifold, catalytic converter, muffler, O2 sensors

Maintenance:

Oil changes, filter replacements, spark plug replacement, fluid flushes (coolant, brake, clutch, transmission, differential), belt inspection/replacement, battery maintenance

Diagnostics:

Troubleshooting guides for common issues, DTC (Diagnostic Trouble Code) interpretation, sensor testing, circuit testing

Repair:

Engine overhaul, transmission rebuild, brake component replacement, suspension component replacement, electrical component repair/replacement, body panel repair

Disassembly And Assembly:

Step-by-step instructions for removing and installing major components and sub-assemblies

Specifications And Tolerances:

Torque specifications, alignment data, gap measurements, fluid capacities

Wiring Diagrams:

Detailed electrical schematics for all vehicle systems

Depth:

Comprehensive (from basic maintenance to complete engine and transmission overhauls, including advanced diagnostics and electrical troubleshooting)

📊 Manual Specifications

Format Details:

PDF (typically, search functionality, bookmarking, printable pages)

Quality Description:

High-resolution, clear diagrams and text, comparable to original factory documentation

Binding Description:

Not applicable for digital download, but original manuals were typically spiral-bound or perfect-bound.

Paper Description:

Not applicable for digital download, but original manuals were printed on durable paper stock.

⚙️ Engine Specifications

Engine Code:

EJ257

Configuration:

2.5L (2457cc) turbocharged and intercooled DOHC 16-valve horizontally opposed (Boxer) four-cylinder engine

Horsepower:

300 hp @ 6000 rpm (SAE Net)

Torque:

300 lb-ft @ 4000 rpm (SAE Net)

Bore X Stroke:

99.5 mm x 79.0 mm

Compression Ratio:

8.4:1

Fuel Delivery:

Multi-point fuel injection (MPI), Sequential electronic fuel injection (SEFI)

Fuel Type:

Premium Unleaded Gasoline (91 octane or higher recommended)

ECU Type:

Denso ECU (specific part number varies, e.g., 22611AG571 for certain configurations)

Coolant Capacity:

Approx. 7.8 liters (16.4 US pints)

Oil Capacity:

5.0 US quarts (4.7 liters) with filter change

Oil Type Recommendation:

5W-30 Synthetic (meeting API SN or equivalent)

🔧 Transmission

Type:

6-speed Manual Transmission

Type:

N/A for WRX STI models of this generation; manual was standard.

Dccd:

Driver's Control Center Differential (DCCD) with automatic and manual modes for torque distribution adjustment.

Transmission Fluid Type:

Subaru Extra-S Gear Oil or equivalent GL-5 75W-90

Transmission Fluid Capacity:

Approx. 3.4 liters (7.2 US pints)

Front Differential Fluid Type:

GL-5 75W-90

Rear Differential Fluid Type:

GL-5 75W-90

📐 Dimensions

Wheelbase:

2629 mm (103.5 in)

Length:

4405 mm (173.4 in)

Width:

1795 mm (70.7 in)

Height:

1445 mm (56.9 in)

Front Track:

1530 mm (60.2 in)

Rear Track:

1535 mm (60.4 in)

Curb Weight:

Approx. 1475 kg (3252 lbs)

Gross Vehicle Weight Rating:

N/A (typically not a primary spec for enthusiast vehicles)

Standard Wheel Size:

17x8 inches (later models/special editions may have 18-inch wheels)

Wheel Bolt Pattern:

5x100 mm

Standard Tire Size:

225/45R17

🛡️ Safety Features

NHTSA Front Crash Rating:

Not specifically tested for all trims, but generally considered safe for its class.

IIHS Crash Test Ratings:

Good in frontal offset, acceptable/good in side impact depending on testing year and specific configuration.

Traction Control:

Subaru Vehicle Dynamics Control (VDC) with AWD integration.

ABS:

4-wheel Anti-lock Braking System (ABS) with Electronic Brake-force Distribution (EBD).

Airbags:

Driver and front passenger airbags, front side-impact airbags, front and rear curtain airbags (depending on trim).

Seatbelts:

3-point front seatbelts with pre-tensioners and load limiters, 3-point rear seatbelts.

Child Anchors:

LATCH (Lower Anchors and Tethers for Children) system.

💡 Technology Features

Audio System:

Factory AM/FM/CD player with (optional) subwoofer. Limited connectivity by modern standards.

Climate Control:

Manual or automatic climate control (depending on trim).

Cruise Control:

Standard cruise control.

Performance Monitoring:

Driver-controlled center differential (DCCD) for on-the-fly AWD tuning is a key performance technology.

Auxiliary Input:

Optional auxiliary input jack (may require adapter or aftermarket installation).

🔧 Maintenance

Oil Change Interval:

Every 3,750 miles (6,000 km) or 6 months, whichever comes first (severe duty) or 7,500 miles (12,000 km) or 12 months (normal duty). Synthetic oil is highly recommended.

Engine Air Filter:

Inspect every 15,000 miles (24,000 km), replace as needed.

Cabin Air Filter:

Replace annually or every 15,000 miles (24,000 km).

Spark Plugs:

Replace every 60,000 miles (96,000 km). Use Iridium-tipped plugs (e.g., NGK PFR7B or similar).

Coolant Flush:

Every 30,000 miles (48,000 km) or 24 months. Use Subaru Super Coolant or equivalent. Ensure proper mixture (50/50).

Timing Belt:

If equipped with a timing belt (EJ257 uses a belt), replacement is critical at 105,000 miles (168,000 km) or 7 years, including tensioner and idler pulleys.

Brake Fluid:

DOT 3 or DOT 4 compatible brake fluid. High-performance fluid recommended for spirited driving.

Clutch Fluid:

DOT 3 or DOT 4 compatible brake fluid (shared reservoir with brakes).

Piston Ringland Failure:

A known issue with the EJ257 engine, particularly when subjected to aggressive tuning or poor maintenance, leading to ringland damage. Proper fueling and detonation prevention are crucial.

Head Gasket Leaks:

While less prevalent than in earlier EJ engines, head gasket issues can still occur, especially with engine modifications or overheating.

Clutch Wear:

Performance driving can lead to accelerated clutch wear, particularly on the OEM clutch. Upgraded clutches are common.

Suspension Bushings:

Wear and tear on suspension bushings can lead to degraded handling and noise over time.

📚 Vehicle History

Heritage Focus:

Subaru's long-standing association with motorsport, particularly in rallying, is the foundation of the WRX and STI lineage, emphasizing AWD and turbocharged performance.

Generation Context:

This generation (GDB) represented a significant styling and chassis update from the previous GC8 generation, moving to a more modern platform with a longer wheelbase and wider track.

Mid Cycle Refresh:

The 2004 model year marked a significant mid-cycle refresh for the GDB chassis, introducing the new engine (EJ257), updated styling (especially the front fascia and headlights), and revised suspension tuning.

Production Plant:

Ota City, Gunma Prefecture, Japan

Production Years For Generation:

2002-2007

🏆 Awards & Recognition

Performance Magazine Accolades:

Consistently ranked as a top performance car by automotive publications during its production run, lauded for its handling and accessible AWD performance.

Motorsport Success:

The Impreza WRX STI platform has a decorated history in World Rally Championship (WRC), winning multiple driver and manufacturer titles, which significantly bolsters the model's pedigree.