VOLKSWAGEN CORRADO 1990 Repair Manual

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 3)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
of vehicle. Depress brake pedal and turn ignition on. Open bleeder
screw and allow fluid to exit until no air is present in fluid. Close
bleeder screw. Turn ignition off and release brake pedal. Perform same
procedure for left rear brake. Ensure fluid level does not go below
minimum level mark.Fig. 1: Locating ABS Components
Courtesy of Volkswagen United States, Inc.
ADJUSTMENTS
PARKING BRAKE
Raise vehicle and support securely. Release parking brake
lever. Apply brake pedal once. Loosen lock nuts. Tighten each
adjusting nut until lever on respective caliper lifts off stop.
Measure gap between stop and lever. Do not move lever off stop more
than .040" (1 mm). Tighten lock nuts. Ensure wheels lock at 3 notches.
NOTE: No other information on adjustments is available.
TROUBLE SHOOTING
HYDRAULIC MODULATOR/PUMP
Depressurize brake system. See DEPRESSURIZING BRAKE SYSTEM.
Turn ignition on. Hydraulic modulator/pump should operate for 60

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 4)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
seconds maximum and then stop. Depress brake pedal a few times; pump
should operate again for a few seconds. If pump motor does not
operate, check electrical system. If pump motor operates for more than
60 seconds, internal or external hydraulic leak may be indicated.
Check for external leaks. If external leak is not found, further
testing may be needed to check for internal leaks.
ANTI-LOCK WARNING LIGHT
Start engine. ANTI-LOCK warning light should come on, then
turn off after a few seconds. If light does not come on when engine is
started, check electrical system. If light comes on and stays on,
fault has been detected by the ECU and testing will be needed. See
SYSTEM TESTING under DIAGNOSIS & TESTING.
DIAGNOSIS & TESTING
SYSTEM TESTING
NOTE: Check battery condition, brake fluid level, electrical
connections and wiring for damage. If fluid level is
incorrect or battery and/or electrical connections are
faulty, correct problem before preceding. Perform each step,
in sequence, to test entire system, except for ECU. If
faulty ECU is suspected, replace with a known good one, and
retest system. Unplug ECU connector for all test steps.
Power Voltage-To-ECU Test
Turn ignition off. Unplug ECU connector. Turn ignition on.
Using a voltmeter, check voltage between ECU connector terminals No. 1
and 2. See Fig. 2. If voltage is 10 volts or more, go to next test. If
voltage is less than 10 volts, check battery, ground, ABS fuse, relay
and wiring. Repair as necessary.Fig. 2: Identifying ECU Connector Terminals
Courtesy of Volkswagen United States, Inc.
ECU Relay Voltage Test
Connect a jumper wire between ECU connector terminals No. 2
and 8. See Fig. 2. Turn ignition on. Using a voltmeter, check voltage
between ECU connector terminals No. 1 and 3. If voltage is 10 volts or
more, go to next test. If voltage is less than 10 volts, check ABS
fuse. If fuse is faulty, replace and retest. If fuse is okay, check
wiring. If wiring is faulty, repair and retest. If wiring is okay,
replace relay and retest.
Brakelight Switch

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 5)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
Turn ignition on. Apply brakes. Check for 12 volts between
terminals No. 12 and 1. If 12 volts are present, brakelight switch is
okay. If 12 volts are not present, check fuse, brakelight switch and
Black/Red wire from brakelight switch to ECU.
Hydraulic Modulator/Pump Relay Voltage Test
1) Turn ignition off. Unplug hydraulic modulator/pump
connector. Depress brake pedal 25 times. Turn ignition on. Using a
voltmeter, measure voltage between ECU connector terminals No. 1 and
32. See Fig. 2. If voltage is 10 volts or more, go to RIGHT REAR WHEEL
SPEED SENSOR VOLTAGE TEST under SYSTEM TESTING.
2) If voltage is less than 10 volts, check hydraulic
modulator/pump fuse. If fuse is okay, check wiring between ECU
connector terminal No. 32 and hydraulic modulator/pump connector
terminal No. 1 (large gauge Red/Black wire). See Figs. 2 and 4-9. If
wiring is not okay, repair wiring, and retest. If wiring is okay,
replace relay, and retest.
Right Rear Wheel Speed Sensor Voltage Test
Connect an AC voltmeter between ECU connector terminals No. 4
and 22. See Fig. 2. Rotate right rear wheel at one revolution per
second. Measure voltage with wheel rotating. If voltage is 0.075 volt
or more, go to next test. If voltage is less than 0.075 volt, check
wheel speed sensor and/or toothed ring for damage, wear and proper
installation. If damage or wear is found, replace faulty component and
retest. If not properly installed, reposition and retest. If
components are okay, replace wheel speed sensor and retest.
Left Rear Wheel Speed Sensor Voltage Test
Connect an AC voltmeter between ECU connector terminals No. 6
and 24. See Fig. 2. Rotate left rear wheel at one revolution per
second. Measure voltage with wheel rotating. If voltage is 0.075 volt
or more, go to next test. If voltage is less than 0.075 volt, check
wheel speed sensor and/or toothed ring for damage, wear and proper
installation. If damage or wear is found, replace faulty component and
retest. If not properly installed, reposition and retest. If
components are okay, replace wheel speed sensor and retest.
Right Front Wheel Speed Sensor Voltage Test
Connect an AC voltmeter between ECU connector terminals No. 7
and 25. See Fig. 2. Rotate right front wheel at one revolution per
second. Measure voltage with wheel rotating. If voltage is 0.075 volt
or more, go to next test. If voltage is less than 0.075 volt, check
wheel speed sensor and/or toothed ring for damage, wear and improper
installation. If damage or wear is found, replace faulty component,
and retest. If component is improperly installed, reposition
component, and retest. If components are okay, replace wheel speed
sensor, and retest.
Left Front Wheel Speed Sensor Voltage Test
Connect an AC voltmeter between ECU connector terminals No. 5
and 23. See Fig. 2. Rotate left front wheel at one revolution per

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 6)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
second. Measure voltage with wheel rotating. If voltage is 0.075 volt
or more, go to next test. If voltage is less than 0.075 volt, check
wheel speed sensor and/or toothed ring for damage, wear and proper
installation. If damage or wear is found, replace faulty component and
retest. If not properly installed, reposition and retest. If
components are okay, replace wheel speed sensor and retest.
ECU Relay Continuity Test
Turn ignition off. Using an ohmmeter, check for continuity
between ECU connector terminals No. 1 and 3, and between terminals No.
1 and 20. See Fig. 2. If there is continuity at both test points, go
to next test. If there is no continuity at either or both test points,
check wiring. If wiring is faulty, repair and retest. If wiring is
okay, replace relay and retest.
Solenoid Valves Ground Circuit Continuity Test
1) Turn ignition off. Remove jumper wire from previous test.
Using an ohmmeter, check for continuity between ECU connector
terminals No. 1 and 11. See Fig. 2. If there is continuity, go to next
step.
2) If continuity does not exist, check for continuity between
ECU connector terminal No. 1 and valve block housing and between
hydraulic modulator and valve block housing. If continuity does not
exist between ECU connector terminal No. 1 and valve block housing,
repair wiring, and retest. If continuity does not exist between
housings, repair as necessary.
3) Reconnect jumper wire between ECU connector terminals No.
1 and 11. Check for continuity between ECU connector terminal No. 11
and valve block connector terminal No. 1 (Brown wire). See Figs. 2, 4-
9. If there is no continuity, repair wiring and retest.
Hydraulic Modulator/Pump Relay Ground Circuit Test
Turn ignition off. Reconnect pressure switch connector.
Depress brake pedal 20 times. Using an ohmmeter, check for continuity
between ECU connector terminals No. 1 and 14. If continuity exists, go
to next test. If continuity does not exist, check for continuity
between pressure switch terminals No. 1 (Brown wire) and 4 (Red/Yellow
or White wire). See Figs. 1 and 4-9. If continuity does not exist,
replace pressure switch, and retest. If continuity exists, check
wiring between ECU terminal No. 14 and pressure switch terminal No. 4.
Repair wiring, and retest.
Low Pressure Warning Switch Test
Turn ignition off. Ensure brake fluid level is okay and fluid
level sensor switch float is in correct position (switch is in closed
position). Ensure accumulator is fully charged and pump is not
operating. Using an ohmmeter, check for continuity between ECU
connector terminals No. 9 and 10. See Fig. 2. If there is continuity,
switch is okay. If contiuity does not exist, check wiring. If wiring
is okay, replace switch, and retest.
Right Rear Wheel Speed Sensor Resistance Test

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 7)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
Turn ignition off. Using an ohmmeter, measure resistance
between ECU connector terminals No. 4 and 22. See Fig. 2. If
resistance is 800-1400 ohms, go to next test. If resistance is not as
specified, check resistance at right rear wheel speed sensor. If
resistance is correct, repair wiring and retest. If resistance is not
correct, replace wheel speed sensor and retest.
Left Rear Wheel Speed Sensor Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 6 and 24. See Fig. 2. If resistance is 800-1400 ohms, go
to next test. If resistance is not as specified, check resistance at
left rear wheel speed sensor. If resistance is correct, repair wiring
and retest. If resistance is not correct, replace wheel speed sensor,
and retest.
Right Front Wheel Speed Sensor Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 7 and 25. See Fig. 2. If resistance is 800-1400 ohms, go
to next test. If resistance is not as specified, check resistance at
right front wheel speed sensor. If resistance is correct, repair
wiring and retest. If resistance is not correct, replace wheel speed
sensor and retest.
Left Front Wheel Speed Sensor Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 5 and 23. See Fig. 2. If resistance is 800-1400 ohms, go
to next test. If resistance is not as specified, check resistance at
left front wheel speed sensor. If resistance is correct, repair
wiring, and retest. If resistance is not correct, replace wheel speed
sensor, and retest.
Right Rear Wheel Speed Sensor Shielding Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 4 and 1. See Fig. 2. If resistance is 20,000 ohms or
more, go to next test. If resistance is less than 20,000 ohms, check
shielding wire for damage. Replace harness if damage is found and
retest.
Left Rear Wheel Speed Sensor Shielding Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 6 and 1. See Fig. 2. If resistance is 20,000 ohms or
more, go to next test. If resistance is less than 20,000 ohms, check
shielding wire for damage. Replace harness if damage is found and
retest.
Right Front Wheel Speed Sensor Shielding Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 7 and 1. See Fig. 2. If resistance is 20,000 ohms or
more, go to next test. If resistance is less than 20,000 ohms, check
shielding wire for damage. Replace harness if damaged, and retest.
Left Front Wheel Speed Sensor Shielding Resistance Test

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 8)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
Using an ohmmeter, measure resistance between ECU connector
terminals No. 5 and 1. See Fig. 2. If resistance is 20,000 ohms or
more, go to next test. If resistance is less than 20,000 ohms, check
shielding wire for damage. Replace harness if damaged, and retest.
ECU Relay Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 1 and 8. See Fig. 2. If resistance is 50-100 ohms, go to
next test. If resistance is not as specified, check wiring. If wiring
is faulty, repair and retest. If wiring is okay, replace relay and
retest. See Fig. 3.Fig. 3: Locating Relays
Courtesy of Volkswagen United States, Inc.
ABS Main Valve Resistance Test
Using an ohmmeter, measure resistance between terminals at
ABS main valve terminals. See Figs. 1 and 4-9. If resistance is 2-5
ohms, ABS main valve is okay. If resistance is not 2-5 ohms, replace
hydraulic modulator.
ABS Main Valve Continuity Test
Using an ohmmeter, check for continuity between ABS main
valve terminal No. 1 (Black wire) and ECU connector terminal No. 18,
and between ABS main valve terminal No. 2 (Brown wire) and ground. See

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 9)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
Figs. 1, 2, 4-9. There should be continuity at both test points. If
there is no continuity at both test points, repair wiring and retest.
Rear Hydraulic Modulator Inlet Valve Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 11 and 17. See Fig. 2. If resistance is 5-7 ohms, go to
next test. If resistance is not 5-7 ohms, measure between hydraulic
modulator block terminals No. 1 (Brown wire) and 5 (Gray wire). See
Fig. 4-9. If resistance is 5-7 ohms, check wiring between hydraulic
modulator and ECU for open circuit. If resistance is not 5-7 ohms,
replace hydraulic modulator.
Right Front Hydraulic Modulator Inlet Valve Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 11 and 15. See Fig. 2. If resistance is 5-7 ohms, go to
next test. If resistance is not 5-7 ohms, measure between hydraulic
modulator terminals No. 1 (Brown wire) and 2 (Yellow wire). See
Fig. 4-9. If resistance is 5-7 ohms, check wiring between hydraulic
modulator and ECU for open circuit. If resistance is not 5-7 ohms,
replace hydraulic modulator.
Left Front Hydraulic Modulator Inlet Valve Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 11 and 35. See Fig. 2. If resistance is 5-7 ohms, go to
next test. If resistance is not 5-7 ohms, measure between hydraulic
modulator terminals No. 1 (Brown wire) and 7 (Blue or Black/Green
wire). See Figs. 4-9. If resistance is 5-7 ohms, check wiring between
valve block and ECU for open circuit. If resistance is not 5-7 ohms,
replace hydraulic modulator.
Rear Hydraulic Modulator Outlet Valve Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 11 and 33. See Fig. 2. If resistance is 3-5 ohms, go to
next test. If resistance is not 3-5 ohms, measure between valve block
terminals No. 1 (Brown wire) and 4 (White wire). See Fig. 4-9. If
resistance is 3-5 ohms, check wiring between hydraulic modulator and
ECU for open circuit. If resistance is not 3-5 ohms, replace hydraulic
modulator.
Right Hydraulic Modulator Block Outlet Valve Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 11 and 34. See Fig. 2. If resistance is 3-5 ohms, go to
next test. If resistance is not 3-5 ohms, measure between hydraulic
modulator terminals No. 1 (Brown wire) and 3 (Green wire). See Fig. 4-
9. If resistance is 3-5 ohms, check wiring between hydraulic modulator
and ECU for open circuit. If resistance is not 3-5 ohms, replace
hydraulic modulator.
Left Front Hydraulic Modulator Outlet Valve Resistance Test
Using an ohmmeter, measure resistance between ECU connector
terminals No. 11 and 16. See Fig. 2. If resistance is 3-5 ohms, go to
next test. If resistance is not 3-5 ohms, measure between hydraulic

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 10)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
modulator terminals No. 1 (Brown wire) and 6 (Black/Blue wire). See
Fig. 4-9. If resistance is 3-5 ohms, check wiring between hydraulic
modulator and ECU for open circuit. If resistance is not 3-5 ohms,
replace hydraulic modulator.
Hydraulic Modulator/Pump Relay Resistance Test
Turn ignition off. Unplug pressure switch connector from
hydraulic modulator. Using an ohmmeter, measure resistance between ECU
connector terminals No. 2 and 14. See Fig. 2. If resistance is 50-100
ohms, go to next test. If resistance is not 50-100 ohms, check wiring.
If wiring is faulty, repair wiring and retest. If wiring is okay,
replace relay and retest.
ABS Main Valve Function Test
Connect a jumper wire between ECU connector terminals No. 2
and 18. See Fig. 2. Depress brake pedal. Turn ignition on. Brake pedal
should rise slightly. If brake pedal did not rise slightly, check
wiring between terminals and hydraulic modulator. If wiring is okay,
replace hydraulic modulator.
Hydraulic Modulator/Pump Test
Turn ignition off. Depress brake pedal 25 times. Turn
ignition on. BRAKE and ANTI-LOCK lights should come on for 2-60
seconds. Pump should operate for 2-60 seconds, then turn off. If
lights do not come on, check wiring and warning light bulbs, and
retest. Also check bulb(s). If lights come on, then turn off, and pump
operates for 60 seconds maximum, then turns off, go to next test. If
pump does not operate and all other preceding tests have been
performed, replace hydraulic modulator/pump.
CAUTION: During VALVE BLOCK FUNCTION TESTS, DO NOT turn ignition on
longer than 60 seconds during any test.
Rear Valve Block Function Test
Connect a jumper wire ECU between ECU connector terminals No.
2, 17 and 33. See Fig. 2. Depress brake pedal. Rear wheels should be
locked up. Turn ignition on. Rear wheels should rotate. If wheels do
not rotate, replace hydraulic modulator. Turn ignition off.
Right Front Valve Block Function Test
Connect a jumper wire ECU between ECU connector terminals No.
2, 15 and 34. See Fig. 2. Depress brake pedal. Right front wheel
should be locked up. Turn ignition on. Right front wheel should
rotate. If wheel do not rotate, replace hydraulic modulator. Turn
ignition off.
Left Front Valve Block Function Test
Connect a jumper wire ECU between ECU connector terminals No.
2, 16 and 35. See Fig. 2. Depress brake pedal. Left front wheel should
be locked up. Turn ignition on. Left front wheel should rotate. If
wheel do not rotate, replace hydraulic modulator. Turn ignition off.

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 11)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
REMOVAL & INSTALLATION
HYDRAULIC MODULATOR/PUMP
Removal & Installation
1) Depressurize brake system. See DEPRESSURIZING BRAKE
SYSTEM. Disconnect negative battery cable. Unplug all electrical
connectors from hydraulic modulator/pump. Identify and disconnect all
hydraulic lines from hydraulic modulator/pump. Plug all line openings.
2) From inside passenger compartment, remove push rod clevis
pin. Remove hydraulic modulator/pump retaining nuts. Remove hydraulic
modulator/pump. To install, reverse removal procedure. Tighten all
fittings to specification. See TORQUE SPECIFICATIONS TABLE at end of
article. Bleed brake system. See BLEEDING BRAKE SYSTEM.
WHEEL SPEED SENSORS
NOTE: To protect magnetic part of sensor, always leave new wheel
speed sensor in special packaging until ready for
installation.
Removal & Installation
Remove bolt retaining wheel speed sensor. Unplug connector.
Remove wheel speed sensor. To install, apply Lubricant (G-000-650) to
sensor. Install sensor, and tighten retaining bolt to 84 INCH lbs. (10
N.m).
TORQUE SPECIFICATIONS
TORQUE SPECIFICATIONS TABLEÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄApplications Ft. Lbs. (N.m)
Brake Lines-To-Hydraulic Modulator/Pump ............... 11 (15)
Hydraulic Modulator/Pump Retaining Nuts ............... 18 (25)
INCH Lbs. (N.m)
Wheel Sensor Retaining Bolt .......................... 84 (9.5)
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ WIRING DIAGRAMS

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 12)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PMFig. 4: Corrado ABS Wiring Diagram (1991)