🏷️ Basic Information

Make:

Subaru

Model:

Impreza

Year:

2004

Generation:

2nd Generation (GD/GG)

Chassis Codes:

GD (Sedan), GG (Wagon)

👋 Introduction

Market Segment:

Compact car, known for its All-Wheel Drive (AWD) system and sporty variants.

Competitors:

Honda Civic, Toyota Corolla, Mazda3, Mitsubishi Lancer, Ford Focus.

Unique Selling Points:

Standard Symmetrical All-Wheel Drive (except for some specific base models), rally-inspired performance (WRX variants), practical hatchback and sedan body styles.

Intended Users:

Professional technicians, DIY enthusiasts, Subaru owners seeking in-depth repair and maintenance knowledge.

📋 Manual Details

Primary Coverage:

Repair and Service for Subaru Impreza 2004 Models

Estimated Page Count:

Over 1500 pages (typical for comprehensive factory service manuals)

Manual Type:

Factory Service Manual (FSM) / Repair Manual

Language:

English

Format:

PDF (Digital Download)

📖 Manual Coverage

Engine Systems:

Engine mechanical, lubrication, cooling, fuel, ignition, emissions control, engine electrical, turbocharger systems (if applicable)

Transmission Systems:

Manual transmission, automatic transmission, clutch, driveshaft, differentials, AWD system

Chassis Systems:

Suspension (front and rear), steering, brakes (front and rear), wheels and tires

Electrical Systems:

Wiring diagrams, lighting, instrument cluster, power accessories, audio system, security system, body control module

Body And Interior:

Exterior body panels, interior trim, seats, airbags, HVAC system, body seals

Maintenance Procedures:

Scheduled maintenance, fluid changes, filter replacements, lubrication, belt inspection and replacement

Repair Procedures:

Component removal and installation, engine overhaul, transmission repair, brake component replacement, suspension component overhaul

Diagnostic Procedures:

Troubleshooting guides, diagnostic trouble codes (DTCs), circuit testing, component testing

Specifications And Tolerances:

Torque specifications, alignment specifications, measurement tolerances, electrical specifications

Depth Of Information:

Comprehensive from basic maintenance to full engine and transmission rebuilds, including electrical diagnostics and body repair.

📊 Manual Specifications

File Type:

PDF

Searchability:

Text-searchable PDF for quick information retrieval.

Image Resolution:

High-resolution images and diagrams for clarity.

Binding Type:

N/A (Digital Download)

Paper Type:

N/A (Digital Download)

⚙️ Engine Specifications

Engine Code Na:

EJ251 (2.5L SOHC Non-Turbo)

Engine Code DOHc Na:

EJ204 (2.0L DOHC Non-Turbo - common in certain markets)

Engine Code Turbo:

EJ205 (2.0L DOHC Turbo - WRX models)

Engine Code Turbo 2.5:

EJ255 (2.5L DOHC Turbo - later WRX models)

Horsepower Na 2.5L:

Approx. 165-175 hp @ 5600-6000 rpm (varies by market and specific engine tune)

Torque Na 2.5L:

Approx. 166-170 lb-ft @ 3600-4000 rpm

Horsepower Turbo 2.0L Wrx:

Approx. 227 hp @ 5600 rpm (WRX)

Torque Turbo 2.0L Wrx:

Approx. 217 lb-ft @ 4000 rpm (WRX)

Fuel Delivery:

Electronic Fuel Injection (EFI)

Fuel Type:

Unleaded gasoline (Octane rating requirements may vary, typically 91+ for turbo models)

Engine Layout:

Horizontally-opposed (Boxer)

Bore Stroke 2.5L:

99.5 mm x 79.0 mm

Compression Ratio Na 2.5L:

9.7:1

🔧 Transmission

Transmission Type Na:

5-speed manual transmission (standard on most non-WRX models)

Transmission Type Auto:

4-speed automatic transmission (optional on most non-WRX models)

Transmission Type Wrx:

5-speed manual transmission (standard on WRX models)

Drivetrain:

Symmetrical All-Wheel Drive (AWD) standard on most models, Front-Wheel Drive (FWD) on some base models in certain markets.

AWD System Type:

Viscous coupling center differential with rear limited-slip differential (for manual transmissions); electronically controlled multi-plate transfer clutch (for automatic transmissions).

📐 Dimensions

Length Sedan:

Approx. 177.0 inches

Length Wagon:

Approx. 175.0 inches

Width:

Approx. 68.1 inches

Height Sedan:

Approx. 56.1 inches

Height Wagon:

Approx. 57.1 inches

Wheelbase:

Approx. 103.0 inches

Curb Weight:

Varies by model and configuration, typically 2900-3200 lbs for non-WRX, 3100-3300 lbs for WRX.

🛡️ Safety Features

NHTSA Frontal Crash Rating:

4 stars (driver and passenger) - based on 2004 testing.

IIHS Front Offset Crash Rating:

Good (for models tested)

ABS:

Standard on most models, optional on some base trims.

E Brake Force Distribution:

Electronic Brake-force Distribution (EBD) often integrated with ABS.

Airbags:

Front airbags standard. Side curtain airbags and front side airbags available on higher trims.

Seatbelts:

Three-point seatbelts with pretensioners for front occupants.

💡 Technology Features

Audio System:

Factory standard radios typically featured AM/FM with CD player. Higher trims might offer premium sound systems.

Display Systems:

Basic climate controls and instrument cluster displays. No advanced infotainment screens typical of modern vehicles.

Cruise Control:

Available on most models.

Traction Control:

Vehicle Dynamics Control (VDC) system available on select models, especially higher trims and WRX variants.

Auxiliary Input:

Not commonly found in factory systems of this era. Aftermarket solutions often required.

🔧 Maintenance

Oil Change Interval:

Typically 3,750 miles or 3 months (severe driving) / 7,500 miles or 6 months (normal driving), refer to manual for exact specifications.

Spark Plug Replacement:

Platinum-tipped spark plugs usually around 60,000-100,000 miles. Refer to manual for exact type and interval.

Timing Belt Replacement:

For EJ251 engines, typically 105,000 miles or 105 months. Crucial for these engines to prevent catastrophic damage. WRX models with EJ205/EJ255 may have different intervals or timing chains.

Engine Oil Spec:

SAE 5W-30 or 5W-40, API SG or higher (refer to manual for specific viscosity and API service classification, especially for turbo models).

Coolant Type:

Subaru Genuine Coolant or equivalent silicate-free, long-life coolant (typically blue).

Transmission Fluid Manual:

API GL-5, SAE 75W-90 Gear Oil.

Transmission Fluid Automatic:

Subaru Genuine ATF-HP or equivalent Dexron III/Mercon compatible fluid (check manual for exact specification).

Differential Fluid Rear:

API GL-5, SAE 75W-90 or 75W-90 LS (Limited Slip) if equipped with LSD.

Head Gaskets:

While less prevalent than in some earlier Subaru EJ engines, some EJ251 engines can still develop head gasket leaks over time, especially with age and heat cycles. Proper torque sequences and quality gaskets are crucial during replacement.

Wrx Ring Land Failure:

Early EJ205 engines in WRX models can be susceptible to ring land failure, particularly when modified or driven hard. The manual will detail engine internals and torque specs important for engine building/rebuilding.

Oil Consumption:

Some EJ engines can exhibit oil consumption. This manual will provide specifications for piston ring end gap and oil control ring clearances, vital for diagnosing and addressing this.

Clutch Wear:

Clutch wear is dependent on driving style, but replacement procedures and specifications for flywheel resurfacing are detailed.

📚 Vehicle History

Subaru Heritage:

Subaru has a long history of producing robust and reliable vehicles, with a particular focus on AWD technology and boxer engines, stemming from its aviation roots.

Impreza Evolution:

The 2004 Impreza represents the second generation (GD/GG), which debuted globally in late 2000. This generation brought a more rounded styling compared to the first generation, and introduced the iconic WRX model to many markets, solidifying its place in performance compact car segments.

Production Location:

Japan (Ota, Gunma Prefecture)

Production Years:

2000-2007 (for the 2nd Generation, with facelift variations occurring mid-cycle)

🏆 Awards & Recognition

Wrx Motorsport Legacy:

The WRX variant is deeply connected to Subaru's successful rally heritage, having achieved multiple World Rally Championship (WRC) driver and manufacturer titles in previous eras, which continued to influence public perception of the model's performance capabilities.

Car And Driver 10Best:

The WRX version of the Impreza was frequently lauded by automotive publications like Car and Driver for its exhilarating performance and handling, often appearing on '10Best' lists in its category during its production run.