Segment:
        
        
            Compact Sports Sedan/Wagon
        
     
    
        
            Target Audience:
        
        
            Enthusiasts, DIY mechanics, Subaru owners seeking to perform their own maintenance and repairs.
        
     
    
    
        
            Competitors:
        
        
            Mitsubishi Lancer Evolution, Honda Civic Si, Mazda3 MPS, Volkswagen Golf GTI
        
     
    
    
        
            All Wheel Drive:
        
        
            Symmetrical All-Wheel Drive (standard on most trims)
        
     
    
        
            Performance Variants:
        
        
            Availability of high-performance WRX and STI models with turbocharged engines and enhanced chassis components.
        
     
    
        
            Practicality:
        
        
            Available in sedan and wagon body styles, offering practicality alongside performance.
        
     
 
    
    
    
        
            Primary Coverage:
        
        
            All service and repair procedures for the 2004 Subaru Impreza
        
     
    
        
            Secondary Coverage:
        
        
            Routine maintenance, diagnostics, troubleshooting, component removal/installation, specifications, wiring diagrams, bodywork, interior/exterior components
        
     
    
    
        
            Estimated Page Count:
        
        
            Varies based on specific engine/trim, but comprehensive manuals typically range from 1500-3000+ pages for this generation.
        
     
    
    
        
            Type:
        
        
            Repair Manual / Service Manual
        
     
    
    
    
    
 
    
    
    
        
            Powertrain:
        
        
            Engine, Engine Lubrication, Cooling, Fuel System, Emissions Control, Ignition System, Intake and Exhaust Systems, Turbocharger (if applicable)
        
     
    
        
            Drivetrain:
        
        
            Manual Transmission, Automatic Transmission, Clutch System, Differential, Driveshaft, Axles, AWD System
        
     
    
        
            Chassis:
        
        
            Steering System, Suspension System (Front and Rear), Brakes (including ABS), Wheels and Tires
        
     
    
        
            Electrical:
        
        
            Body Electrical System, Powertrain Control Module (PCM), Engine Control, Lighting, Instrumentation, Audio System, Power Accessories, Supplemental Restraint System (SRS)
        
     
    
        
            Body And Interior:
        
        
            Body Panels, Doors, Windows, Seats, Interior Trim, HVAC System, Climate Control, Body Sealing
        
     
    
    
        
            Routine Maintenance:
        
        
            Oil and filter changes, air filter replacement, cabin air filter replacement, spark plug replacement, fluid level checks and top-offs (coolant, brake fluid, power steering fluid, transmission fluid, differential fluid)
        
     
    
        
            Tune Up And Engine Repair:
        
        
            Valve adjustment, timing belt/chain inspection and replacement (depending on engine variant), cylinder head removal/installation, piston and ring service, crankshaft and bearing service, complete engine rebuilding
        
     
    
        
            Transmission And Drivetrain Repair:
        
        
            Clutch replacement, manual transmission internal repair, automatic transmission overhaul, differential service and repair, driveshaft and CV joint replacement
        
     
    
        
            Suspension And Steering Repair:
        
        
            Shock absorber and strut replacement, control arm service, ball joint replacement, tie rod end replacement, power steering pump and rack and pinion service
        
     
    
        
            Brake System Service:
        
        
            Brake pad and rotor replacement, brake caliper service, brake fluid bleeding, ABS system diagnostics and repair
        
     
    
        
            Electrical Diagnostics:
        
        
            Troubleshooting electrical faults using wiring diagrams, component testing (sensors, actuators, modules), SRS system diagnostics and repair
        
     
    
        
            Body And Trim Repair:
        
        
            Door panel removal, seat removal, bumper repair/replacement, interior trim panel replacement
        
     
    
    
        
            Depth:
        
        
            Comprehensive, covering basic maintenance to complete engine and transmission rebuilds, including detailed diagnostic procedures and troubleshooting trees.
        
     
    
        
            Illustrations:
        
        
            Detailed step-by-step instructions with diagrams and photographic illustrations for clarity.
        
     
    
        
            Special Tools:
        
        
            Identification of required special tools for specific repair procedures.
        
     
    
        
            Troubleshooting:
        
        
            Inclusion of diagnostic trouble codes (DTCs), symptom-based troubleshooting guides, and repair procedures for common issues.
        
     
 
    
    
    
        
            Engine Code Non Turbo:
        
        
            EJ253 (2.5L SOHC Boxer), EJ20 (various versions, e.g., EJ205 for WRX)
        
     
    
        
            Engine Code Turbocharged:
        
        
            EJ205 (2.0L Turbocharged Boxer for WRX), EJ257 (2.5L Turbocharged Boxer for STI)
        
     
    
    
        
            Displacement 2 5I:
        
        
            2.5 Liters (2457 cc)
        
     
    
        
            Horsepower 2 5I:
        
        
            Approx. 173 hp @ 5600 rpm
        
     
    
        
            Torque 2 5I:
        
        
            Approx. 166 lb-ft @ 4000 rpm
        
     
    
    
        
            Displacement Wrx:
        
        
            2.0 Liters (1994 cc)
        
     
    
        
            Horsepower Wrx:
        
        
            Approx. 227 hp @ 6000 rpm
        
     
    
        
            Torque Wrx:
        
        
            Approx. 217 lb-ft @ 4000 rpm
        
     
    
    
        
            Displacement Sti:
        
        
            2.5 Liters (2457 cc)
        
     
    
        
            Horsepower Sti:
        
        
            Approx. 300 hp @ 6000 rpm
        
     
    
        
            Torque Sti:
        
        
            Approx. 300 lb-ft @ 4000 rpm
        
     
    
    
        
            Fuel Delivery:
        
        
            Multi-point Fuel Injection (MPI)
        
     
    
        
            Recommended Fuel:
        
        
            Unleaded gasoline (87 octane for non-turbo, 91+ octane for WRX/STI)
        
     
 
    
    
    
        
            Length:
        
        
            Approx. 4415 mm (173.8 in)
        
     
    
        
            Width:
        
        
            Approx. 1740 mm (68.5 in)
        
     
    
        
            Height:
        
        
            Approx. 1410 mm (55.5 in)
        
     
    
    
        
            Length:
        
        
            Approx. 4465 mm (175.8 in)
        
     
    
        
            Width:
        
        
            Approx. 1740 mm (68.5 in)
        
     
    
        
            Height:
        
        
            Approx. 1445 mm (56.9 in)
        
     
    
    
        
            Curb Weight:
        
        
            Varies by trim and body style, typically ranging from 2900 to 3400 lbs.
        
     
    
        
            Wheelbase:
        
        
            2535 mm (99.8 in)
        
     
    
        
            Track Width Front:
        
        
            Approx. 1480 mm (58.3 in)
        
     
    
        
            Track Width Rear:
        
        
            Approx. 1475 mm (58.1 in)
        
     
    
    
        
            Ground Clearance Sti:
        
        
            Approx. 135 mm (5.3 in) (Lowered for performance)
        
     
 
    
    
    
        
            NHTSA Front Impact:
        
        
            5-Star (for driver and passenger)
        
     
    
        
            NHTSA Side Impact:
        
        
            4-Star (for front and rear passengers)
        
     
    
    
        
            ABS:
        
        
            Anti-lock Braking System (ABS)
        
     
    
        
            E Brake:
        
        
            Electronic Brake-force Distribution (EBD) (often integrated with ABS)
        
     
    
        
            Traction Control:
        
        
            Available Traction Control System (TCS)
        
     
    
    
        
            Airbags:
        
        
            Driver and front passenger airbags, available side airbags
        
     
    
        
            Srs:
        
        
            Supplemental Restraint System (SRS) including airbag system and pre-tensioner seatbelts
        
     
    
        
            Rollover Protection:
        
        
            Reinforced passenger compartment structure
        
     
 
    
    
    
        
            Oil Change Interval:
        
        
            Typically every 3,750 to 7,500 miles (6,000 to 12,000 km) or 6 months, whichever comes first, depending on driving conditions. Consult the manual for specific recommendations based on oil type used.
        
     
    
        
        Service Intervals Filters
    
 
    
        
            Air Filter Replacement:
        
        
            Every 15,000 to 30,000 miles (24,000 to 48,000 km) or as needed based on inspection.
        
     
    
        
            Cabin Filter Replacement:
        
        
            Typically every 15,000 to 30,000 miles (24,000 to 48,000 km).
        
     
    
        
        Service Intervals Spark Plugs
    
 
    
        
            Spark Plug Replacement:
        
        
            For standard EJ253: ~60,000 miles. For EJ205/EJ257: Varies, often with specialized spark plugs recommended.
        
     
    
    
        
            Coolant Replacement:
        
        
            Initial change at 30,000 miles, then every 30,000 miles thereafter. (Subaru Super Coolant is often recommended).
        
     
    
        
            Transmission Fluid Manual:
        
        
            Check periodically, change typically around 60,000-100,000 miles (check manual for exact recommendation).
        
     
    
        
            Transmission Fluid Automatic:
        
        
            Check periodically, change typically around 30,000-60,000 miles depending on use. (Use Dexron III or equivalent).
        
     
    
        
            Differential Fluid Front Rear:
        
        
            Check periodically, change typically around 30,000-60,000 miles.
        
     
    
    
        
            Engine Oil Non Turbo:
        
        
            SAE 5W-30 or 10W-30 (API SG, SH, or SJ classification). Consult manual for specific viscosity based on climate.
        
     
    
        
            Engine Oil Turbocharged:
        
        
            SAE 5W-30 or 5W-40 (API SJ, SL, or SM classification) - often a higher quality synthetic is recommended.
        
     
    
        
            Coolant:
        
        
            Subaru Super Coolant (Blue) or equivalent. 50/50 mix with distilled water.
        
     
    
        
            Brake Fluid:
        
        
            DOT 3 or DOT 4
        
     
    
        
            Power Steering Fluid:
        
        
            Subaru Genuine ATF or Dexron III/Mercon equivalent
        
     
    
        
            Manual Transmission Fluid:
        
        
            GL-5 Gear Oil (SAE 75W-90 recommended)
        
     
    
        
            Automatic Transmission Fluid:
        
        
            Dexron III or equivalent
        
     
    
    
        
            Head Gaskets:
        
        
            While less common on EJ253 (SOHC) engines compared to earlier EJ25D (DOHC), head gasket leaks can still occur. Subaru used multiple revisions of head gaskets.
        
     
    
        
            Turbo Failure Wrx Sti:
        
        
            Turbocharger failures can occur, especially with improper maintenance, oil starvation, or aggressive driving without adequate cool-down periods.
        
     
    
        
            Clutch Wear:
        
        
            Clutch wear is generally considered normal for performance applications, but premature wear can result from abuse or towing.
        
     
    
        
            Suspension Components:
        
        
            Worn suspension bushings, ball joints, and wheel bearings are common wear items, particularly on performance models driven hard.
        
     
    
        
            Oil Consumption:
        
        
            Some EJ engines, especially with higher mileage, may exhibit increased oil consumption.
        
     
 
    
    
    
        
            Subaru Heritage:
        
        
            Subaru, a division of Subaru Corporation (formerly Fuji Heavy Industries), is known for its boxer engines and standard All-Wheel Drive systems, particularly in its rally-bred performance vehicles.
        
     
    
    
        
            Second Gen Introduction:
        
        
            The second generation (GD/GG) Impreza debuted for the 2002 model year, with the 2004 model representing a significant update with revised styling and performance enhancements, especially for the WRX and STI models.
        
     
    
        
            Performance Heritage:
        
        
            The Impreza WRX and STI have a strong heritage in motorsports, particularly in the World Rally Championship (WRC), where they achieved significant success and influenced the development of production models.
        
     
    
    
        
            Manufacturing Location:
        
        
            Japan