🏷️ Basic Information

Make:

Subaru

Model:

Impreza WRX STi

Year:

2004

Chassis Code:

GDB-E (Applicable to later 2004 models, specifically the 'E' generation)

Engine Code Primary:

EJ257

👋 Introduction

Market Niche:

High-performance, rally-bred compact sedan, positioned as a driver's car with AWD capabilities and potent turbocharged engine.

Key Competitors:

Mitsubishi Lancer Evolution, Ford Focus RS, Volkswagen Golf GTI (though the WRX STi is generally positioned higher in performance).

Performance Focus:

Emphasis on turbocharged power, Symmetrical All-Wheel Drive, and performance-oriented chassis tuning.

Rally Heritage:

Direct lineage and technology derived from Subaru's successful World Rally Championship campaigns.

📋 Manual Details

Coverage:

Comprehensive service, maintenance, repair, and troubleshooting for the 2004 Subaru Impreza WRX STi.

Page Count:

Estimated 2000+ pages (typical for a complete factory service manual of this era and detail level)

Manual Type:

Factory Service Manual (FSM) / Professional Repair Manual

Language:

English

Format:

Digital (likely PDF, as indicated by 'ma......' suggesting a manual file)

📖 Manual Coverage

Engine System:

Detailed diagnostics, overhaul procedures, component testing, fuel injection, ignition system, emissions control, cooling system, lubrication system.

Transmission System:

Manual transmission (TY856 6-speed), clutch system, driveline components, differentials (front, center DCCD, rear).

Braking System:

Hydraulic system, ABS, brake component inspection and replacement (discs, pads, calipers), bleeding procedures.

Suspension Coverage:

Front and rear suspension geometry, strut assembly, control arms, bushings, alignment specifications, wheel bearing service.

Electrical Coverage:

Wiring diagrams, component locations, fuse and relay identification, diagnostic trouble codes (DTCs), ECU functions, lighting, power accessories.

Body Chassis Coverage:

Body panel removal and installation, interior trim, exterior lighting, chassis lubrication, frame specifications.

HVAC Coverage:

Air conditioning system diagnosis, refrigerant handling, heater core, climate control unit.

Fuel System Coverage:

Fuel pump, injectors, fuel pressure regulator, evaporative emission control (EVAP).

Scheduled Maintenance:

Oil changes, filter replacements, spark plug replacement, fluid flushes, belt inspections and replacements.

Troubleshooting:

Diagnostic flowcharts, symptom-based troubleshooting, common fault identification.

Engine Rebuild:

Detailed disassembly, inspection, repair, and reassembly of the EJ257 engine, including torque specifications for all critical fasteners.

Transmission Overhaul:

Complete teardown, inspection, and reassembly of the TY856 6-speed manual gearbox.

Drivetrain Service:

CV axle replacement, driveshaft inspection, differential fluid changes, DCCD (Driver's Control Center Differential) system service.

Brake Service:

Brake pad and rotor replacement, caliper overhaul, brake line replacement, ABS bleeding.

Suspension And Steering:

Strut replacement, ball joint service, tie rod end replacement, power steering system diagnosis.

Electrical Diagnostics:

Wiring harness repair, sensor testing, actuator testing, ECM/PCM troubleshooting.

Depth Level:

Expert; covers from basic maintenance to complete engine and transmission rebuilds, including advanced diagnostics and component-level repair.

📊 Manual Specifications

Digital Format:

PDF (Searchable text is highly probable for a professional manual)

Print Quality Suitability:

Suitable for professional printing or digital viewing; contains detailed diagrams and schematics.

Binding Type:

N/A (Digital format)

Paper Type:

N/A (Digital format)

⚙️ Engine Specifications

Engine Type:

2.5-liter, DOHC, turbocharged, intercooled horizontally opposed flat-four (Boxer engine)

Horsepower:

300 bhp @ 6000 rpm (approximate, often rated slightly higher in real-world dyno tests for the STi variant)

Torque:

300 lb-ft @ 4000 rpm (approximate, often rated slightly higher in real-world dyno tests for the STi variant)

Fuel Injection:

Multi-point fuel injection with Denso top-feed 650cc injectors.

Internals:

Forged pistons and connecting rods, sodium-filled exhaust valves, reinforced crankshaft.

Radiator Type:

High-performance aluminum radiator, often requiring specific Subaru coolant.

Oil Type And Capacity:

SAE 5W-30 synthetic oil recommended, approximately 5.8 quarts (5.5 liters) capacity with filter. Check manual for exact specification.

🔧 Transmission

Transmission Type:

6-speed manual transmission (TY856)

Optional Transmissions:

None (STi models were exclusively manual)

Dccd:

Driver's Control Center Differential (DCCD) allowing manual adjustment of front/rear torque split, or automatic mode.

Transmission Fluid:

Manual transmission fluid (MTF) for the gearbox and front differential, typically 75W-90 GL-5. Rear differential fluid 75W-90 GL-5. Refer to manual for exact Subaru specifications and capacities.

📐 Dimensions

Length:

4,405 mm (173.4 in)

Width:

1,740 mm (68.5 in)

Height:

1,425 mm (56.1 in)

Wheelbase:

2,625 mm (103.3 in)

Curb Weight:

Approx. 1,440 kg (3,175 lbs)

Trunk Volume:

Approx. 0.326 m³ (11.5 cu ft)

🛡️ Safety Features

NHTSA Ratings:

Likely achieved good ratings for its time, but specific NHTSA ratings for the 2004 WRX STi may vary. Refer to official archives for precise data.

AWD System:

Subaru Symmetrical All-Wheel Drive with DCCD and viscous center differential.

ABS:

Standard Anti-lock Braking System.

Airbags:

Front driver and passenger airbags, potentially side airbags depending on trim.

Body Structure:

Reinforced chassis and crumple zones.

💡 Technology Features

Head Unit:

Standard AM/FM/CD player with potential for premium audio system depending on trim. Manual may cover head unit removal and speaker replacement.

Dccd Control:

Key technological feature for torque distribution management, covered in detail for operation and troubleshooting.

Connectivity Features:

Limited by 2004 standards; typically basic audio input/output. No advanced Bluetooth or USB connectivity in stock form.

🔧 Maintenance

Oil Change Interval:

Typically every 3,000-5,000 miles (5,000-8,000 km) or 6 months, especially for performance driving. Refer to manual for precise Subaru recommendation.

Timing Belt Replacement:

Every 105,000 miles (168,000 km) or 7 years. Crucial due to interference engine design. Include tensioner and idler pulleys.

Coolant Type:

Subaru Super Coolant (Blue) or equivalent silicate-free long-life coolant. Capacity approx. 8.7 quarts (8.2 liters).

Brake Fluid Type:

DOT 3 or DOT 4 brake fluid. Capacity approx. 0.7-1.0 quart (0.7-0.9 liters) for a full flush.

Ring Land Failure:

A known potential issue in EJ257 engines under high load or with poor tuning, particularly on modified vehicles. Manual will detail proper maintenance and diagnostics.

Clutch Wear:

Can wear faster than average due to performance driving and the STi's power delivery. Manual covers clutch inspection and replacement.

Suspension Bushings:

Wear in control arm and sway bar bushings can lead to noise and handling degradation over time.

📚 Vehicle History

Subaru Motorsports:

Deep roots in rallying, with numerous WRC championships and a reputation for durable, capable performance vehicles.

Gdb Chassis Generation:

This 2004 model falls into the 'GDB-E' generation (or final update of the GD chassis), featuring distinctive 'bug eye' headlights and specific STi enhancements.

Manufacturing Location:

Japan

🏆 Awards & Recognition

Performance Accolades:

Consistently praised by automotive media for its performance, handling, and AWD capabilities, often winning 'Best Performance Car' categories in its segment during its production run.

Driving Dynamics:

Renowned for exceptional handling, steering feedback, and braking performance, especially in adverse conditions due to AWD.

Emissions Compliance:

Designed to meet emissions standards for its respective market. Manual will detail emission control systems and diagnosis.