🏷️ Basic Information

Make:

Subaru

Model:

Impreza WRX STI

Year:

2003-2004

Chassis Code:

GD (Sedan) / GG (Wagon)

Engine Code Primary:

EJ257 (2.5L Boxer Turbocharged DOHC)

👋 Introduction

Positioning:

The Subaru Impreza WRX STI of this era (GD/GG chassis) was a dominant force in rally-inspired performance sedans and wagons, targeting enthusiasts seeking high performance, all-wheel-drive capability, and a raw driving experience.

Competitors:

Mitsubishi Lancer Evolution, Ford Focus RS, Volkswagen Golf R, Audi S3

Performance Focus:

Engineered for performance, featuring Subaru's signature Symmetrical All-Wheel Drive, a potent turbocharged boxer engine, and a driver-focused chassis.

Rally Heritage:

Direct lineage from Subaru's highly successful World Rally Championship (WRC) vehicles, translating to exceptional handling and durability under demanding conditions.

Manual Availability:

Offered with both manual and automatic transmissions, though the manual is highly sought after by enthusiasts for its engagement.

📋 Manual Details

Coverage:

Full Service, Repair, Diagnostics, Electrical, Bodywork, Troubleshooting

Estimated Page Count:

2000+ (typical for comprehensive factory manuals)

Type:

Factory Service Manual / Workshop Manual

Language:

English

Format:

Digital (PDF, ePub, etc.) - Instant Download

📖 Manual Coverage

Engine Mechanical:

Engine assembly, cylinder head, block, crankshaft, pistons, camshafts, valve train, timing belt/chain, lubrication system, cooling system

Engine Management:

Fuel injection system, ignition system, emissions control, turbocharger system, sensors (MAF, O2, knock, etc.), ECU diagnosis

Transmission Manual:

Clutch system, gearbox assembly, gear selection, synchronizers, bearings, seals, flywheel, hydraulic system (if applicable)

Transmission Automatic:

Torque converter, planetary gear sets, valve body, hydraulic control, transmission control module (TCM), fluid cooler

Drivetrain:

Front differential, rear differential (Viscous Center Diff/Driver Controlled Center Diff), driveshafts, CV joints, wheel hubs

Suspension:

Front strut assembly, rear multi-link suspension, control arms, bushings, sway bars, coil springs, dampers

Brakes:

Front and rear disc brakes, ABS system, brake calipers, master cylinder, brake lines, parking brake

Steering:

Power steering system, steering rack, tie rods, steering column, steering wheel

Electrical System:

Battery, charging system, starter motor, lighting (headlights, taillights, interior), fuses, relays, wiring diagrams

Body And Interior:

Body panels, doors, hood, trunk, bumpers, seats, dashboard, trim, HVAC system, interior lighting

Safety Systems:

Airbag system, seat belts, SRS module, warning lights

Preventative Maintenance:

Oil changes, filter replacements, fluid checks/changes, spark plug replacement, belt inspection/replacement

Troubleshooting Diagnostics:

Diagnostic Trouble Codes (DTCs), symptom-based diagnostics, wiring diagram interpretation, component testing

Repair Procedures:

Engine overhaul, transmission rebuild, suspension component replacement, brake caliper overhaul, electrical component repair

Installation Replacement:

Component replacement (alternator, starter, radiator, etc.), body panel replacement, interior trim installation

Specifications Data:

Torque specifications, clearances, fluid capacities, diagnostic parameters, component identification

Wheel Alignment:

Specifications and procedures for wheel alignment adjustments.

Exhaust System:

Diagnosis and repair of exhaust components, catalytic converter, mufflers.

Body Repair:

Procedures for minor body panel repairs, dent removal, and alignment.

HVAC System:

Diagnosis and repair of air conditioning, heating, and ventilation systems, including refrigerant handling.

Depth:

Comprehensive: From basic fluid changes to complete engine and transmission rebuilds, including detailed electrical schematics and diagnostic procedures.

📊 Manual Specifications

File Type:

PDF (typically high resolution, searchable text)

Quality:

High-quality digital reproduction of original factory documentation

Binding:

N/A (Digital Download)

Paper:

N/A (Digital Download)

Scope:

Factory Authorized Content - covers all aspects of repair and maintenance as intended by the manufacturer.

⚙️ Engine Specifications

Engine Type:

Horizontally Opposed (Boxer), Turbocharged, Intercooled

Displacement:

2.5 Liters (2457cc)

Valvetrain:

DOHC (Double Overhead Camshafts), 4 valves per cylinder

Bore X Stroke:

99.5 mm x 80.0 mm

Compression Ratio:

8.4:1

Fuel Delivery:

Sequential Multi-Port Fuel Injection (MPI)

Turbocharger:

IHI VF39 (or similar depending on specific market/trim)

Horsepower:

Approx. 300 PS (296 hp; 221 kW) at 6000 rpm (varies by market)

Torque:

Approx. 300 lb-ft (407 Nm) at 4000 rpm (varies by market)

Fuel Type:

Premium Unleaded Gasoline (91 octane or higher recommended)

Fuel Tank Capacity:

60 Liters (15.9 US Gallons)

🔧 Transmission

Manual Transmission:

6-Speed Manual (TY757)

Automatic Transmission:

4-Speed Automatic (4EAT or similar)

AWD System:

Subaru Symmetrical All-Wheel Drive with Driver Controlled Center Differential (DCCD) on manual models, viscous coupling center differential on automatic models.

Manual Clutch Type:

Hydraulically Actuated, Single Dry Plate

📐 Dimensions

Length:

4415 mm (Sedan) / 4465 mm (Wagon)

Width:

1740 mm

Height:

1440 mm (Sedan) / 1455 mm (Wagon)

Wheelbase:

2625 mm

Ground Clearance:

135 mm

Curb Weight:

Approx. 1470-1520 kg (depending on transmission and body style)

Gross Vehicle Weight Rating:

Not specified in product info, but typically around 1900-2000 kg

🛡️ Safety Features

NHTSA Ratings:

Refer to specific government safety agency reports for individual model year ratings. Generally good for its class and era.

ABS:

Standard Anti-lock Braking System

Traction Control:

Standard Traction Control System (TCS)

E-Diff:

Driver Controlled Center Differential (DCCD) on manual models for torque distribution adjustment.

Airbags:

Front airbags, side airbags (optional/standard depending on trim)

Seat Belts:

Three-point seat belts with pretensioners

Body Structure:

Reinforced body structure with crumple zones

💡 Technology Features

Head Unit:

Factory radio with CD player, potentially cassette player depending on market and original spec. Aftermarket upgrades are common.

Audio System:

Standard speaker system; premium options may have existed.

Cruise Control:

Standard electronic cruise control

Limited Electronics:

This era is relatively free of complex electronic driver aids compared to modern vehicles, focusing on mechanical and driver control.

Aux Input:

May be present, but Bluetooth or USB connectivity is generally absent in factory units.

🔧 Maintenance

Oil Change Interval:

Every 3,000-5,000 miles (5,000-8,000 km) or 3-6 months, depending on driving conditions (severe duty recommended for performance driving).

Spark Plug Replacement:

Typically every 30,000-60,000 miles (48,000-96,000 km) with iridium plugs, check manual for specific type and interval.

Timing Belt Replacement:

105,000 miles (168,000 km) or 7 years for vehicles with a timing belt (EJ257 typically uses a belt, confirm in manual).

Engine Oil:

5W-30 Synthetic, API SG or higher (check manual for exact Subaru spec, e.g., Subaru Extra Vehicle Safe Oil)

Coolant:

Subaru Super Coolant (Blue) or equivalent long-life coolant (50/50 mix with distilled water).

Transmission Fluid Manual:

API GL-5 Gear Oil, SAE 75W-90 (e.g., Subaru Extra Vehicle Safe Gear Oil)

Transmission Fluid Automatic:

Subaru ATF-HP (High Performance) or equivalent approved ATF.

Differentials Fluid:

API GL-5 Gear Oil, SAE 75W-90 for front and rear differentials. Center differential fluid requirements vary; check manual.

Head Gaskets:

While improved over earlier generations, EJ engines can still be susceptible to head gasket leaks, especially if overheated or modified without proper tuning. The EJ257 is generally more robust than earlier EJ25s.

Ringlands:

High-performance tuning without proper supporting modifications (fueling, cooling) can lead to ringland failure in the pistons, particularly on older or higher-mileage engines.

Turbocharger:

The IHI VF39 turbo can be prone to issues if oil is not changed regularly or if debris enters the intake. Wastegate actuator failure is also a possibility.

Clutch Wear:

Aggressive driving can lead to premature clutch wear, especially on manual transmission models.

Suspension Bushings:

Original suspension bushings can wear over time, leading to clunks and imprecise handling.

📚 Vehicle History

Subaru Performance:

Subaru has a strong heritage in motorsports, particularly in the World Rally Championship (WRC), where the Impreza was a dominant force, fostering the WRX and STI brand.

Gd Gg Chassis:

This generation (2000-2007) marked a significant evolution, with the WRX STI becoming a distinct model from the standard Impreza, inheriting more race-bred technology.

2003 Update:

The 2003 model year brought the 'Blobeye' facelift, with redesigned headlights, front bumper, and grille, and technical revisions to the engine and chassis.

2004 Update:

Further refinements were made, including potential minor power bumps and chassis enhancements, leading into the STI's widespread recognition.

Manufacturing Location:

Gunma Prefecture, Japan

🏆 Awards & Recognition

Rally Dominance:

The Impreza WRX STI platform, in general, has achieved significant acclaim and numerous victories in motorsport, particularly WRC. This manual covers a model derived from that lineage.

Performance Reviews:

Consistently praised by automotive media for its exhilarating performance, all-wheel-drive grip, and driver engagement.