1997 SUBARU LEGACY battery

B4M0520
U: TROUBLE CODE 42
HIGH VOLTAGE
—Source voltage is high—
DIAGNOSIS:

Power source voltage of the ABS/TCS control module is
more than 18 V.

Faulty ABS/TCS control module

Faulty harness/connector
TROUBLE SYMPTOM:

ABS does not operate.

TCS does not operate.
1. Check generator.

OK
Not OK
Repair generator.
2. Check battery terminal.

OK
Not OK
Repair battery terminal.
3. Check input voltage of ABS/TCS control mod-
ule.

OK
Not OK
Repair harness/connector.
4. Check ground circuit of ABS/TCS control
module.

OK
Not OK
Repair harness/connector.
Replace ABS/TCS control module.




11 2
4-4bBRAKES
10. Diagnostic Chart with Select Monitor

1. Supplemental Restraint System
“Airbag”
Airbag system wiring harness is routed near the ABS con-
trol module, ABS sensor and hydraulic control unit.
CAUTION:

All Airbag system wiring harness and connectors
are colored yellow. Do not use electrical test equip-
ment on these circuit.

Be careful not to damage Airbag system wiring har-
ness when servicing the ABS control module, ABS
sensor and hydraulic control unit.
2. Pre-inspection
Before performing diagnostics, check the following items
which might affect ABS problems:
A: MECHANICAL INSPECTION
1. POWER SUPPLY
1) Measure battery voltage and specific gravity of electro-
lyte.
Standard voltage: 12 V, or more
Specific gravity: Above 1.260
2) Check the condition of the main and other fuses, and
harnesses and connectors. Also check for proper ground-
ing.
2. BRAKE FLUID
1) Check brake fluid level.
2) Check brake fluid leakage.
3. BRAKE DRAG
Check brake drag.
4. BRAKE PAD AND ROTOR
Check brake pad and rotor.
5. TIRE SPECIFICATIONS, TIRE WEAR AND AIR
PRESSURE
Check tire specifications, tire wear and air pressure. to 4-2 [S1A0].>
2
4-4cBRAKES [ABS 5.3 TYPE]
1. Supplemental Restraint System“Airbag”- 2. Pre-inspection

1. Supplemental Restraint System
“Airbag”
Airbag system wiring harness is routed near the ABS con-
trol module, ABS sensor and hydraulic control unit.
CAUTION:

All Airbag system wiring harness and connectors
are colored yellow. Do not use electrical test equip-
ment on these circuit.

Be careful not to damage Airbag system wiring har-
ness when servicing the ABS control module, ABS
sensor and hydraulic control unit.
2. Pre-inspection
Before performing diagnostics, check the following items
which might affect ABS problems:
A: MECHANICAL INSPECTION
1. POWER SUPPLY
1) Measure battery voltage and specific gravity of electro-
lyte.
Standard voltage: 12 V, or more
Specific gravity: Above 1.260
2) Check the condition of the main and other fuses, and
harnesses and connectors. Also check for proper ground-
ing.
2. BRAKE FLUID
1) Check brake fluid level.
2) Check brake fluid leakage.
3. BRAKE DRAG
Check brake drag.
4. BRAKE PAD AND ROTOR
Check brake pad and rotor.
5. TIRE SPECIFICATIONS, TIRE WEAR AND AIR
PRESSURE
Check tire specifications, tire wear and air pressure. to 4-2 [S1A0].>
2
4-4cBRAKES [ABS 5.3 TYPE]
1. Supplemental Restraint System“Airbag”- 2. Pre-inspection

7. Diagnostics Chart for ABS Warning
Light Circuit and Diagnosis Circuit
Failure
A: ABS WARNING LIGHT DOES NOT COME
ON.
DIAGNOSIS:

ABS warning light circuit is open or shorted.
TROUBLE SYMPTOM:

When ignition switch is turned ON (engine OFF), ABS
warning light does not come on.
7A1.Check if other warning lights turn on.
7A2.Check ABS warning light bulb.
7A3.Check wiring harness.
7A4.Check battery short of relay box.
7A5.Check poor contact in connector between
combination meter and ABSCM.




14
4-4cBRAKES [ABS 5.3 TYPE]
7. Diagnostics Chart for ABS Warning Light Circuit and Diagnosis Circuit Failure

7A2
CHECK ABS WARNING LIGHT BULB.
1) Turn ignition switch to OFF.
2) Remove combination meter.
3) Remove ABS warning light bulb from combination
meter.
: Is ABS warning light bulb OK?
: Go to step7A3.
: Replace ABS warning light bulb.
B4M0791A
7A3
CHECK WIRING HARNESS.
1) Disconnect connector from ABSCM.
2) Disconnect connector (F50) from relay box.
3) Turn ignition switch to ON.
4) Measure voltage between connector (F49) and chassis
ground.
: Connector & terminal
(F49) No. 54 (+) — Chassis ground ():
Is voltage 12 V?
: Go to next step.
: Repair broken wire in harness or connector.
5) Turn ignition switch to OFF.
6) Measure voltage between ABSCM connector (F49) and
chassis ground.
: Connector & terminal
(F49) No. 54 (+) — Chassis ground ():
Is voltage less than 3 V?
: Go to step7A4.
: Repair battery short of harness.
16
4-4cBRAKES [ABS 5.3 TYPE]
7. Diagnostics Chart for ABS Warning Light Circuit and Diagnosis Circuit Failure

B4M0792B
7A4CHECK BATTERY SHORT OF RELAY
BOX.
1) Disconnect connector from relay box.
2) Turn ignition switch to ON.
3) Measure voltage between relay box and chassis
ground.
: Connector & terminal
To (F50) No. 2 (+)—Chassis ground ():
Is voltage 0 V?
: Go to next step.
: Replace relay box.
4) Turn ignition switch OFF.
5) Measure voltage between relay box and chassis
ground.
: Connector & terminal
To (F50) No. 2 (+)—Chassis ground ():
Is voltage 0 V?
: Go to step7A5.
: Replace relay box.
7A5CHECK POOR CONTACT IN CONNEC-
TOR BETWEEN COMBINATION METER
AND ABSCM.
: Is there poor contact in connectors between
combination meter and ABSCM?
: Repair connector.
: Replace ABSCM.
17
4-4cBRAKES [ABS 5.3 TYPE]
7. Diagnostics Chart for ABS Warning Light Circuit and Diagnosis Circuit Failure

B: ABS WARNING LIGHT DOES NOT GO
OFF.
DIAGNOSIS:

ABS warning light circuit is open or shorted.
TROUBLE SYMPTOM:

When starting the engine and while ABS warning light is
kept ON.
7B1.Check installation of ABSCM connector.
7B2.Check generator.
7B3.Check battery terminal.
7B4.Check power supply of ABSCM.
7B5.Check ground circuit of ABSCM.
7B6.Check wiring harness.
7B7.Check relay box.
7B8.Check valve relay.
7B9.Check hydraulic control unit.
7B10.Check diagnosis terminal.
7B11.Check diagnosis line.
7B12.Check poor contact in ABSCM connector.











18
4-4cBRAKES [ABS 5.3 TYPE]
7. Diagnostics Chart for ABS Warning Light Circuit and Diagnosis Circuit Failure

B4M0430
7B2
CHECK GENERATOR.
1) Start the engine.
2) Idle the engine.
3) Measure voltage between generator and chassis
ground.
: Terminal
Generator B terminal (+)—Chassis ground
():
Is voltage 10—15 V?
: Go to step7B3.
: Repair generator.
7B3
CHECK BATTERY TERMINAL.
Turn ignition switch to OFF.
: Is there poor contact at battery terminal?
: Repair battery terminal.
: Go to step7B4.
B4M0796A
7B4
CHECK POWER SUPPLY OF ABSCM.
1) Disconnect connector from ABSCM.
2) Start engine.
3) Idle the engine.
4) Measure voltage between ABSCM connector and chas-
sis ground.
: Connector & terminal
(F49) No. 28 (+)—Chassis ground ():
Is voltage 10—15 V?
: Go to step7B5.
: Repair ABSCM power supply circuit.
20
4-4cBRAKES [ABS 5.3 TYPE]
7. Diagnostics Chart for ABS Warning Light Circuit and Diagnosis Circuit Failure