Subaru Impreza 2003, Service Manual

Page: 2349 / 3610

ABS-9
ABS (DIAGNOSTICS)
GENERAL DESCRIPTION
3. General Description
A: CAUTION
1. SUPPLEMENTAL RESTRAINT SYSTEM
“AIRBAG”
Airbag system wiring harness is routed near the
ABS wheel speed sensor, ABS control module and
hydraulic control unit.
CAUTION:
• All airbag system wiring harness and con-
nectors are colored yellow. Do not use electri-
cal test equipment on these circuit.
• Be careful not to damage the airbag system
wiring harness when servicing the ABS wheel
speed sensor, ABS control module and hydrau-
lic control unit.
B: INSPECTION
Before performing diagnostics, check the following
items which might affect ABS problems:
1. BATTERY
Measure the battery voltage and specific gravity of
electrolyte.
Standard voltage: 12 V, or more
Specific gravity: Above 1.260
2. BRAKE FLUID
1) Check the brake fluid level.
2) Check the brake fluid leakage.
3. HYDRAULIC UNIT
Check the hydraulic unit.
• With brake tester <Ref. to ABS-9, CHECKING
THE HYDRAULIC UNIT ABS OPERATION WITH
BRAKE TESTER, INSPECTION, ABS Control
Module and Hydraulic Control Unit (ABSCM&H/
U).>
• Without brake tester <Ref. to ABS-8, CHECK-
ING THE HYDRAULIC UNIT ABS OPERATION
BY PRESSURE GAUGE, INSPECTION, ABS
Control Module and Hydraulic Control Unit (AB-
SCM&H/U).>
4. BRAKE DRAG
Check for brake drag.
5. BRAKE PAD AND ROTOR
Check the brake pad and rotor.
• Front <Ref. to BR-27, INSPECTION, Front Brake
Pad.> and <Ref. to BR-30, INSPECTION, Front
Disc Rotor.>
• Rear <Ref. to BR-39, INSPECTION, Rear Brake
Pad.> and <Ref. to BR-40, INSPECTION, Rear
Disc Rotor.> or <Ref. to BR-48, INSPECTION,
Rear Drum Brake Shoe.> and <Ref. to BR-49, IN-
SPECTION, Rear Drum Brake Drum.>
6. TIRE
Check the tire specifications, tire wear and air pres-
sure. <Ref. to WT-2, SPECIFICATIONS, General
Description.>