Subaru 1997 Impreza - Trouble Code 21 (Front RH); Trouble Code 23 (Front LH); Trouble Code 25 (Rear RH); Trouble 27 (Rear LH)

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Specifications3
Dimensions3
Weight7
General Precautions8
Before Starting Service8
While Working8
Treatment for Used Engine Oil8
Environmental Protection Precautions9
Handling an at Vehicle9
Full-Time AWD MT Models9
Speedometer Test9
Brake Test10
Chassis Dynamometer Test10
Tire Balance Test10
Towing11
Non-Turbo Full Time AWD at Models12
Turbo at Models13
Precaution for Supplemental Restraint System (Airbag)16
Identification Number and Label Locations17
Recommended Fuel, Lubricants, Sealants and Adhesives19
Fuel19
Fuels Containing Alcohol19
Lubricants20
Fluid21
Coolant21
Sealants22
Adhesives22
Tightening Torque of Standard Bolts and Nuts23
Lifting, Towing and Tie-Down Points24
Garage Jack24
Pantograph Jack, Safety Stand and Lift25
Support Locations26
Pantograph Jack26
Lift26
Safety Stand26
Towing and Tie-Down Hooks27
Front Hood Stay Installation28
At the Check and General Maintenance28
When Wider Hood Opening Is Necessary28
Schedule of Inspection and Maintenance Servies29
Drive Belts Inspection31
Drive Belts Replacement31
Front Side Belt32
Rear Side Belt32
Camshaft Drive Belt (Timing Belt) Replacement33
Camshaft Drive Belt (Timing Belt) Installation36
Camshaft Drive Belt (Timing Belt) Inspection36
Engine Oil Replacement38
Engine Oil Inspection40
Engine Oil Filter Replacement41
Replace Engine Coolant and Inspect Cooling System, Hoses and Connections42
Replacement of Coolant42
Relationship of Subaru Coolant Concentration and Freezing Temperature44
Procedure to Adjust the Concentration of the Coolant45
Replace Fuel Filter and Inspect Fuel System, Lines and Connections47
Fuel Piping and Connections48
Air Cleaner Element Replacement49
Spark Plugs Replacement50
Idle Mixture Inspection and Adjustment51
Transmission/Differential Lubricants Replacement53
Front Differential (Automatic Transmission)54
Rear Differential (AWD Model)55
Automatic Transmission Fluid Replacement56
Brake Fluid Replacement57
Disc Brake Pads and Discs/Front and Rear Axle Boots and Axle Shaft Joint Portions59
Disc Brake Pad and Disc Inspection59
Front and Rear Axle Boots60
Brake Lining and Drums61
Rear Drum Brake Inspection61
Parking Brake62
Rear Drum Brake Adjustment63
Parking Brake Adjustment63
Brake Line Inspection64
Service Brake Checking64
Parking Brake System66
Brake Servo System66
Mechanical Clutch Type Inspection and Adjustment67
Hill-Holder68
Hydraulic Clutch Type69
Steering and Suspension System70
Steering Wheel Inspection70
Steering Shaft Joint71
Gearbox71
Tie-Rod72
Power Steering Fluid Level72
Power Steering Fluid for Leaks73
Hoses of Oil Pump for Damages73
Power Steering Pipes for Damage73
Gearbox Boots74
Fitting Bolts and Nuts74
Suspension System74
Front and Rear Wheel Bearing Lubricant Inspection79
Front Wheel Bearing79
Rear Wheel Bearing80
Valve Clearance Inspection81
Emission Control System and Vacuum Fitting82
System Application82
Three-Way Catalyst85
A/F Control System86
Ignition Control System86
Evaporative Emission Control System87
Fuel Cut Valve88
Fuel Cap89
Canister90
Purge Control Solenoid Valve91
Two-Way Valve91
Engine Section93
Engine (DOHC)94
Engine (DOHC) General95
Timing Belt96
Belt Tensioner Adjuster97
Belt Cover98
Camshaft99
Cylinder Head100
Cylinder Block101
Crankshaft101
Piston102
Engine Cooling System103
Engine Cooling System General104
Cooling Lines104
Water Pump Mechanism105
Mechanical Seal106
Thermostat107
Radiator Fan Description108
Engine Cooling System Function109
Fuel Injection System (Turbo Model)113
Air Line General116
Mass Air Flow Sensor116
Throttle Body116
Throttle Position Sensor117
Idle Air Control Solenoid Valve118
Fuel Line General119
Pressure Regulator120
Fuel Injector120
Turbocharger System121
Turbocharger Unit122
Lubrication of Turbocharger123
Cooling of Turbocharger123
Regulation of Supercharging Pressure124
Basic Function of the Wastegate Valve124
Concept of the Wastegate Valve Control125
Intercooler126
Wastegate Control Solenoid Valve126
Pressure Sensor127
Pressure Sources Switching Solenoid Valve127
Air By-Pass Valve128
Sensor and Switch129
Oxygen Sensor129
Engine Coolant Temperature Sensor131
Crankshaft Position Sensor131
Camshaft Position Sensor132
Knock Sensor133
Vehicle Speed Sensor133
Control System General134
Control System Input and Output Signals134
Fuel Injection Control135
Fuel Injection Characteristics135
Correction Coefficients136
Air-Fuel Ratio Feedback Coefficient "Alpha"139
Learning Control System139
Ignition System Control140
Idle Air Control142
Canister Purge Control142
Radiator Fan Control143
Fuel Pump Control143
A/C Cut Control144
Power Supply Control144
On-Board Diagnosis System145
Function of On-Board Diagnosis145
Basic Operation of On-Board Diagnosis System146
Fail-Safe Function146
Trouble Codes and Fail-Safe Operation147
Fuel Pump150
Fuel Filter151
Fuel Injection System153
Supplemental Restraint System "Airbag"154
Pre-Inspection154
Power Supply154
Caps and Plugs154
Intake Manifold Vacuum Pressure155
Fuel Pressure155
Engine Grounding155
Electrical Unit Location156
Sensor and Solenoid Valve156
Module and Relay159
Schematic161
Control Module I/O Signal163
Diagnostics Chart for On-Board Diagnosis System165
Basic Diagnostics Procedure165
How to Read Trouble Code166
List of Trouble Code167
Read Memory Mode168
D-Check Mode169
Clear Memory Mode170
Diagnostics Chart for Engine Starting Failure171
Basic Diagnostics Chart171
Control Unit Power Supply and Ground Line172
Check Main Relay173
Check Power Supply Circuit of ECM173
Check Ground Circuit of ECM173
Crankshaft Position Sensor Circuit174
Camshaft Position Sensor Circuit175
Check Ignition System for Sparks178
Check each Spark Plug Cord178
Check Power Supply Circuit for Ignition Coil178
Check Ignition Coil178
Check Harness Connector between Ignitor and Ignition Coil179
Check Input Signal for Ignitor179
Check Harness Connector of Ignitor Ground Circuit179
Check Harness Connector between ECM and Ignitor179
Fuel Pump Circuit181
Check Operating Sound of Fuel Pump183
Check Ground Circuit of Fuel Pump183
Check Power Supply to Fuel Pump183
Check Harness Connector between Fuel Pump and Fuel Pump Relay183
Check Harness Connector between ECM and Fuel Pump Relay184
Fuel Injector Circuit185
Check Operation of each Fuel Injector187
Check Power Supply to Fuel Injector187
Check each Fuel Injector187
Check Harness Connector between ECM and each Fuel Injector187
Check Input Signal for ECM.191
Check Harness Connector between ECM and Crankshaft Position Sensor191
Check Crankshaft Position Sensor192
Starter Switch193
Check Operation of Starter Motor195
Check Harness Connector between ECM and Ignition Switch195
Check Harness Connector between ECM and Camshaft Position Sensor198
Check Camshaft Position Sensor199
Engine Coolant Temperature Sensor Trouble Codes200
Check Engine Coolant Temperature Sensor202
Check Harness Connector between ECM and Engine Coolant Temperature Sensor202
Trouble Code (22)203
Knock Sensor Diagnosis203
Input Signal for ECM205
Check Knock Sensor205
Check Harness Connector between ECM and Knock Sensor205
Trouble Code (23)206
Mass Air Flow Sensor Diagnosis206
Check Input Signal for ECM208
Check Power Supply to Mass Air Flow Sensor208
Check Harness Connector between ECM and Mass Air Flow Sensor208
Trouble Code (24)209
Idle Air Control Solenoid Valve Diagnosis209
Check Idle Air Control Solenoid Valve210
Check Power Supply Line to Idle Air Control Solenoid Valve210
Trouble Code (31)211
Throttle Position Sensor Diagnosis211
Check Harness Connector between ECM and Throttle Position Sensor213
Check and Adjust Throttle Position Sensor214
Trouble Code (32)215
Check Harness Connector between ECM and Oxygen Sensor217
Check Oxygen Sensor Heater Circuit217
Check Oxygen Sensor217
Trouble Code (33)218
Vehicle Speed Sensor Diagnosis218
Check Ground Circuit of Vehicle Speed Sensor 2220
Check Power Supply Circuit of Vehicle Speed Sensor 2221
Trouble Code (38)222
Torque Control Signal Diagnosis222
Check Output Signal from ECM223
Check Harness Connector between ECM and TCM223
Trouble Code (44)224
Wastegate Control Solenoid Valve Diagnosis224
Trouble Code (45)226
Pressure Sensor, Pressure Sources Switching Solenoid Valve Diagnosis226
Check Input and Output Signals on ECM228
Check Rubber Hose to Contact Intake Manifold Pressure228
Check Pressure Sensor228
Check Pressure Sources Switching Solenoid Valve228
Check Harness Connector between ECM and Pressure Sensor229
Check Harness Connector between ECM and Pressure Sources Switching Solenoid Valve229
Check Power Supply to Pressure Sources Switching Solenoid Valve229
Trouble Code (51)230
Neutral Position Switch Diagnosis230
Check Neutral Position Switch231
Check Harness Connector between ECM and Neutral Position Switch231
Park/Neutral Position Switch (AT) Diagnosis232
Check Harness Connector between ECM and Inhibitor Switch233
Check Inhibitor Switch Ground Circuit233
Clutch Outline235
Clutch Operation236
Hydraulic Application Type237
Manual Transmission and Differential238
Reverse Check Mechanism Construction238
Reverse Check Mechanism Operation239
When 5Th and Reverse Side Is Selected239
When Shift Is Made to 5Th240
When Shift Is Made from 5Th to Reverse240
When Shift Is Made to Reverse241
Center Differential Construction242
Center Differential Mechanism of Viscous Coupling243
Torque Characteristics243
"Hump" Phenomenon244
During Turns at Low Speeds245
Acceleration During Standing Starts on a "Low" Road245
Driving on Rough Roads246
AWD System T-Type247
Limited Slip Differential (LSD)248
AWD System Operation249
When Right and Left Wheels Turn at Equal Speed249
When Right and Left Wheels Turn at Different Speeds250
Service Procedures for LSD250
Front Suspension251
Rear Suspension252
Front Axle General253
Front Drive Shaft254
AWD Turbo Model255
Rear Drive Shaft256
Tilt Steering Column257
Tilt Mechanism257
Imbedded Ball Type Energy-Absorbing Mechanism257
Vehicle Without Airbag257
Vehicles with Airbag258
Steering Support Beam258
Power Steering System259
Hydraulic System259
Gearbox Assembly260
Power Cylinder260
Control Valve261
Oil Pump & Tank265
Vane Pump266
Flow Control Valve266
Disc Brake271
Pad Wear Indicator271
Frictional Material of Brake Pads271
Master Cylinder272
Brake Fluid Level Indicator272
Brake Booster273
Brake Booster "Off"273
Brake Booster "ON"274
Brake Booster under Medium Load274
Brake Booster under Full-Load Conditions275
Brake Booster Released275
Brake Booster with no Vacuum276
Proportioning Valve277
Operation During Normal Conditions277
Operation in Case of Circuit Failure278
Failure of Primary Circuit278
Failure of Secondary Circuit278
Proportioning Valve (with ABS Models)279
Anti-Lock Brake System (ABS) Feature281
Functions of Sensors and Actuators282
Theory of ABS Control284
ABS Sensor285
ABS Control Module (ABSCM)285
ABS Control Cycle Curves286
ABS Warning Light287
G Sensor288
Hydraulic Control Unit (H/U)289
During Normal Braking290
Pressure "Decrease" Action with ABS in Operation291
Pressure "Hold" Action with ABS in Operation292
Pressure "Increase" Action with ABS in Operation293
Parking Brake (Rear Disc Brake)294
Set Parking Brake295
Release Parking Brake295
Parking Brake (Rear Drum Brake)296
Brakes297
Mechanical Inspection298
Warning Light Illumination Patterm299
Electrical Components Location300
Brakes Schematic302
I/O Signal Voltage303
I/O Signal Diagram305
Check List for Interview307
Inspection Mode310
Trouble Codes310
Calling up a Trouble Code310
Clearing Memory311
Diagnostics Chart for ABS Warning Light Circuit and Diagnosis Circuit Failure312
ABS Warning Light Does Not Come on312
Check if Other Warning Lights Turn on314
Check ABS Warning Light Bulb314
Check Wiring Harness314
Check Battery Short of Relay Box315
Check Poor Contact in Connectors315
ABS Warning Light Does Not Go off316
Check Installation of ABSCM Connector318
Check Generator318
Check Battery Terminal318
Check Ground Circuit of ABSCM.319
Check Relay Box319
Check Contact Point of Valve Relay320
Check Hydraulic Control Unit321
Check Diagnosis Terminal321
Check Diagnosis Line321
Check Poor Contact in ABSCM Connector322
Trouble Code Does Not Appear323
Diagnostics Chart with Trouble Code by ABS Warning Light326
Trouble Code 21 (Front RH)327
Trouble Code 23 (Front LH)327
Trouble Code 25 (Rear RH)327
Trouble 27 (Rear LH)327
Check ABS Sensor329
Check Battery Short of ABS Sensor329
Check Harness/Connector between ABSCM and ABS Sensor330
Check Battery Short of Harness331
Check Installation of ABS Sensor331
Check Installation of Tone Wheel332
Check ABS Sensor Gap332
Check Hub Runout332
Check ABSCM333
Check any Other Trouble Codes Appearance333
Trouble Code 22 (Front RH)334
Trouble Code 24 (Front LH)334
Trouble Code 26 (Rear RH)334
Trouble Code 28 (Rear LH)334
Check ABS Sensor Signal337
Check Contamination of ABS Sensor of One Wheel338
Check Damage of ABS Sensor or Tone Wheel338
Check Resistance of ABS Sensor339
Check Ground Short of ABS Sensor339
Trouble Code 29344
Abnormal ABS Sensor Signal344
Check if the Wheels Have Turned Freely for a Long Time346
Check Tire Specifications346
Check Tire Pressure346
Trouble Code 31 (Front RH)350
Trouble Code 33 (Front LH)350
Trouble Code 35 (Rear RH)350
Trouble Code 37 (Rear LH)350
Trouble Code 32 (Front RH)356
Trouble Code 34 (Front LH)356
Trouble Code 36 (Rear RH)356
Trouble Code 38 (Rear LH)356
Trouble Code 41362
Abnormal ABS Control Module362
Trouble Code 44368
A Combination of at Control Abnormal368
Trouble Code 46373
Abnormal G Sensor Power Supply Voltage373
Trouble Code 51378
Abnormal Valve Relay378
Trouble Code 52393
Abnormal Motor And/Or Motor Relay393
Trouble Code 54406
Abnormal Stop Light Switch406
Trouble Code 56409
Abnormal G Sensor Output Voltage409
Pedal System and Control Cables415
Pedal Effort Reducing Mechanism415
Hydraulic Clutch Pedal System416
Heater System417
Switch Function418
Mode Selector Switch and Air Flow419
Air Distribution Ratio420
System Flow420
Blower System421
Air Conditioning Cycle422
Compressor423
Air Conditioning System: Suction424
Air Conditioning System: Compression424
Air Conditioning System: Discharge425
Trigger Valve426
When Compressor Is Stopped427
When Compressor Is Restarted427
When Compressor Is in Regular Operation427
Compressor Saving Sensor428
Magnet Clutch429
When Compressor Starts or When Load Is Low433
Check Valve434
Lubrication434
Temperature Sensor435
Condenser Mechanism436
Receiver Drier437
Abnormal Low-Pressure Operation440
Abnormal High-Pressure Operation441
Evaporator445
Expansion Valve446
Compressor Clutch "ON" Delay System449
Compressor Control System449
Thermo Control Amplifier450
Acceleration Cut System450
F.I.C.D.451
Fan Control452
Sunroof454
Tilt-Up Mechanism454
Sunroof Motor455
Limit Switch455
Slide Operation456
Open Operation456
Closed Operation457
Drain Tube Layout459
Door Checker460
Door Construction460
Window Glass461
Rear Gate461
Supplemental Restraint System463
SRS Airbag System Installation463
SRS Airbag System Function464
Airbag Control Module466
Front Sensor466
Safety Sensor467
Airbag Module468
Airbag Connector469
Connector Coupled to Airbag Control Module469
Connector between Harnesses469
Steering Roll Connector470
Airbag Warning Light470
Wire Harness470
Electrical Component Location471
Tools for Diagnostics473
Test Harness C475
Airbag Resistor476
Diagnostics Chart for On-Board Diagnostic System477
On-Board Diagnostic478
Clear Memory478
Diagnostics Chart with Trouble Code484
How to Read Trouble Codes485
Trouble Code 02486
Front Sensor and Harness Inspection487
Airbag Main Harness Inspection487
Trouble Code 03488
Front Sensor (LH and RH) Inspection488
Trouble Code 04489
Trouble Code 11490
Airbag Control Module Inspection490
Fuse No. 8 Inspection491
Trouble Code 12492
Trouble Code 13493
Trouble Code 14494
Double Lock Inspection for Connectors (AB9) and (AB10)495
Airbag Control Module Double Lock Inspection at Connectors (AB4) (AB5) (AB6)495
Roll Connector Double Lock Inspection at Connectors (AB2) and (AB7)495
Trouble Code 21496
Trouble Code 22497
Trouble Code 23498
Front Sensor Inspection499
Trouble Code 24500
Trouble Code 31501
Trouble Code 32503
Airbag Warning Light Remains off507
Airbag Warning Light Unit Inspection508
Warning Light Indicated Trouble Code, then Normal Code509
Selection of Check Parts510
Engine Electrical System515
Starter515
Generator515
Main Fuse and Relay Box517
Joint Box518
Ignition Switch Description519
Front Wiper520
Front Washer System520
Rear Wiper521
Rear Washer System521
Combination Meter522
Warning and Indicator Light522
Telltale (Graphic Monitor)524
Tachometer525
Water Temperature Gauge526
Fuel Gauge527
Power Window529
Power Door Lock530
Vehicle Speed Sensor 2531
Immobiliser System532
Malfunction Indicator Light Blinks536
Immobiliser Indicator Light Remains off537
Diagnostics Chart for Indicator Light540
Check Immobiliser Indicator Light Comes on541
Check IMM ECM Circuit541
Check Combination Meter Circuit542
Check Immobiliser Indicator Light Circuit in Combination Meter543
Diagnostics Chart with Select Monitor546
Wiring Diagram548
Wiring Diagram General Description549
How to Determine an Open Circuit556
How to Determine a Short-Circuit556
How to Use Wiring Diagram559
Connector Sketch560
Wire Tracing on Extended Wiring Diagrams560
Symbols of Wire Connection and Crossing560
Power Supply Routing560
How to Use Super Multiple Junction (SMJ)561
Explanation of SMJ Shown in the Wiring Diagram562
Anti-Lock Brake System567
Charging System Wiring Diagram571
Combination Meter Wiring Diagram572
Door Lock System Wiring Diagram573
Engine Electrical System Wiring Diagram574
Front Log Light System Wiring Diagram578
Front Wiper and Washer System Wiring Diagram579
Fuel Gauge System Wiring Diagram580
Full Time Dual-Range System Wiring Diagram581
Horn and Cigarette Lighter System Wiring Diagram582
Headlight Beam Leveler System Wiring Diagram583
Headlight Washer System Wiring Diagram584
Immobiliser System Wiring Diagram585
Lighting (Headlight) System Wiring Diagram586
Oil Pressure and Temperature Gauge System Wiring Diagram589
Parking Brake and Brake Fluid Level Warning System Wiring Diagram590
Power Window System Wiring Diagram591
Radiator Fan System Wiring Diagram593
Rear Fog Light System Wiring Diagram594
Rear Window Defogger System Wiring Diagram595
Rear Wiper and Washer System Wiring Diagram596
Remote Control Rearview Mirror System Wiring Diagram597
Spot Light, Room Light, Luggage and Trunk Room Light System Wiring Diagram598
SRS (Airbag System) Wiring Diagram599
Starting System Wiring Diagram600
Stop Light System Wiring Diagram601
Sunroof System Wiring Diagram602
Turn Signal and Hazard System Wiring Diagram603
Front Wiring Harness and Ground Point Wiring Diagram604
Bulkhead Wiring Harness and Ground Point (in Engine Room)606
Engine Wiring Harness, Transmission Cord and Ground Point608
Bulkhead Wiring Harness (in Compartment)610
Instrument Panel Wiring Harness and Ground Point612
Rear Wiring Harness and Ground Point614

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Subaru 1997 Impreza - Trouble Code 21 (Front RH); Trouble Code 23 (Front LH); Trouble Code 25 (Rear RH); Trouble 27 (Rear LH)

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