🏷️ Basic Information Identification Make: Subaru Model: Impreza Year: 2004 Engine Variant: 2.5L (gasoline) Codes Chassis Code: GDA/GDB (WRX/STI variants), GGA (Wagon) Engine Code: EJ253 (Naturally Aspirated), EJ255/EJ257 (Turbocharged) 👋 Introduction Market Position Segment: Compact/Subcompact Sedan and Wagon, known for its sporty handling and All-Wheel Drive (AWD) capability. Target Audience: Enthusiast drivers, DIY mechanics, and owners seeking comprehensive repair and maintenance information. Competitive Analysis Key Competitors: Honda Civic, Toyota Corolla, Mazda3, Mitsubishi Lancer. Unique Selling Proposition: Standard Symmetrical All-Wheel Drive (on most models), Subaru's boxer engine configuration, rally-inspired WRX and STI variants. Key Features Powertrain Options: Naturally aspirated 2.5L boxer engine and turbocharged 2.0L/2.5L boxer engines (WRX/STI). Drivetrain: Symmetrical All-Wheel Drive (standard on most trims). 📋 Manual Details Coverage Areas Primary Coverage: 2004 Subaru Impreza 2.5L (gasoline) Trim Level Coverage: All trim levels including RS, Outback Sport, WRX (turbocharged 2.0L/2.5L) and potentially STI (2.5L turbocharged) depending on specific manual variations. Page Count Estimated Page Count: Over 2000 pages (typical for a comprehensive factory service manual) Manual Type Type: Factory Service Repair Manual Language Language: English Format Format: Digital (PDF), potentially printable sections 📖 Manual Coverage Systems Covered Engine Management: ECU diagnosis, sensor inputs/outputs, fuel control, ignition timing, emission control systems (EVAP, EGR), drive-by-wire throttle control (if applicable to specific trims). Engine Mechanical: Engine assembly/disassembly, cylinder head, block, crankshaft, pistons, connecting rods, valve train, timing belt/chain, oil pump, cooling system, lubrication system. Fuel System: Fuel pump, fuel filter, fuel injectors, fuel lines, fuel pressure regulator, fuel tank, EVAP system. Transmission Manual: Clutch system, gearshift linkage, transmission disassembly/assembly, gear ratios, shift forks, synchronizers, bearings. Transmission Automatic: Torque converter, transmission fluid control, valve body, planetary gear sets, clutches, bands, electronic controls, shift solenoids. Drivetrain: Front and rear differentials, transfer case (AWD systems), driveshafts, CV joints, wheel bearings. Suspension: Front MacPherson struts, rear multi-link suspension, control arms, sway bars, bushings, springs, shock absorbers. Steering: Power steering system (hydraulic/electric), steering rack, tie rods, steering column, wheel alignment specifications. Brakes: Front and rear brake systems (disc/drum), ABS system, brake fluid, master cylinder, calipers, rotors, brake lines, parking brake. Electrical System: Battery, alternator, starter motor, wiring diagrams, fuses, relays, lighting system, horn, ignition system. HVAC: Air conditioning system (compressor, condenser, evaporator, refrigerant), heater core, blower motor, climate control system. Body And Interior: Body panels, doors, hood, trunk, windows, seats, dashboard, trim components, body sealing. Safety Systems: Airbag system, seatbelt pretensioners, SRS warning lights and diagnosis. Procedures Included Routine Maintenance: Oil changes, filter replacements, fluid checks and changes, spark plug replacement, air filter replacement. Engine Repair: Complete engine overhaul, cylinder head gasket replacement, piston ring replacement, bearing replacement, timing belt replacement. Transmission Service: Clutch replacement, transmission fluid flush and replacement, internal transmission repairs. Brake Service: Brake pad and rotor replacement, caliper servicing, brake bleeding, ABS component replacement. Suspension And Steering Repair: Ball joint replacement, tie rod end replacement, control arm bushing replacement, strut and shock absorber replacement, power steering pump replacement. Electrical Diagnostics: Troubleshooting electrical faults using wiring diagrams, component testing, diagnostic trouble codes (DTCs). HVAC Repair: Refrigerant recharge, compressor replacement, blower motor replacement, leak detection. Bodywork And Trim: Panel replacement, door alignment, interior trim removal and installation. Troubleshooting: Systematic diagnostic procedures for common and uncommon vehicle issues. Technical Depth Diagnostic Capability: Advanced diagnostic procedures, including component testing, circuit analysis, and use of diagnostic scan tools. Repair Scope: Covers everything from basic maintenance to complete engine and transmission rebuilds, including specialized procedures for AWD systems and turbocharged engines. Specification Detail: Provides precise torque specifications, clearances, fluid capacities, and electrical resistance values for all major components. 📊 Manual Specifications File Format Digital Format: PDF (Portable Document Format) Print Quality Diagram Clarity: High-quality, clear diagrams and illustrations. Text Readability: Easy-to-read text sections, optimized for digital viewing and printing. Binding Type Digital Access: Downloadable file, accessible on computers, tablets, and smartphones. Paper Type Digital Nature: N/A (Digital Format) ⚙️ Engine Specifications Primary Engine Engine Type: Naturally Aspirated Boxer-4 Cylinder (EJ253) Displacement: 2.5 Liters (2457 cc) Bore X Stroke: 99.5 mm x 79.0 mm Compression Ratio: 9.7:1 Valve Train: DOHC, 16 Valves Performance Horsepower Na: Approximately 165-175 hp @ 5600-5800 rpm (varies slightly by specific model/trim) Torque Na: Approximately 166-170 lb-ft @ 4000 rpm (varies slightly by specific model/trim) Horsepower Turbo: WRX: Approx. 227-230 hp @ 5600 rpm; STI: Approx. 300 hp @ 6000 rpm Torque Turbo: WRX: Approx. 235-237 lb-ft @ 3600-4000 rpm; STI: Approx. 300 lb-ft @ 4000 rpm Fuel System Fuel Delivery: Electronic Fuel Injection (EFI) Fuel Type: Unleaded gasoline (87 octane recommended for NA, 91+ octane for WRX/STI) Ignition System: Distributorless Ignition System (DIS) with coil-on-plug 🔧 Transmission Standard Transmission Type: 5-speed Manual (all models) Optional Transmission Type: 4-speed Automatic (available on non-WRX models) Features AWD Integration: Symmetrical All-Wheel Drive with viscous coupling center differential (manual) or electronically controlled AWD (automatic). Sti Transmission: 6-speed manual transmission with DCCD...