1990 VOLKSWAGEN CORRADO brake sensor

ANTI-LOCK BRAKE SAFETY PRECAUTIONS
Article Text
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
ARTICLE BEGINNING
GENERAL INFORMATION
Anti-Lock Brake Safety Precautions
* PLEASE READ THIS FIRST *
This article is intended for general information purposes
only. This information may not apply to all makes and models. If
vehicle is equipped with Anti-Lock Brake System (ABS), refer to
appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section for
description, operation, depressurizing, testing, system bleeding,
trouble shooting and servicing of specific system.
WARNING: Failure to depressurize ABS could lead to physical injury.
ANTI-LOCK BRAKE SAFETY PRECAUTIONS
WARNING: Failure to depressurize ABS could lead to physical injury.
* NEVER open a bleeder valve or loosen a hydraulic line
while ABS is pressurized.
* NEVER disconnect or reconnect any electrical connectors
while ignition is on. Damage to ABS control unit may result.
* DO NOT attempt to bleed hyudarulic system without first
referring to the appropriate ANTI-LOCK BRAKE SYSTEM article
in the BRAKES section.
* Only use specially designed brake hoses/lines on ABS equipped
vehicles.
* DO NOT tap on speed sensor components (sensor, sensor rings).
Sensor rings must be pressed into hubs, NOT hammered into
hubs. Striking these components can cause demagnetization or
a loss of polarization, affecting the accuracy of the speed
signal returning to the ABS control unit.
* DO NOT mix tire sizes. Increasing the width, as long as tires
remain close to the original diameter, is acceptable. Rolling
diameter must be identical for all 4 tires. Some
manufacturers recommend tires of the same brand, style and
type. Failure to follow this precaution may cause inaccurate
wheel speed readings.
* DO NOT contaminate speed sensor components with grease. Only
use recommended coating, when system calls for an
anti-corrosion coating.
* When speed sensor components have been removed, ALWAYS check
sensor-to-ring air gaps when applicable. These specifications
can be found in each appropriate article.
* ONLY use rocommended brake fluids. DO NOT use silicone brake
fluids in an ABS equipped vehicle.
* When instlling transmittion devices (CB's, telephones, etc.)
on ABS equipped vehicles, DO NOT locate the antenna near the
ABS control unit (or any control unit).

ANTI-LOCK BRAKE SYSTEM
Article Text
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
ARTICLE BEGINNING
1990-92 BRAKES
Volkswagen Anti-Lock Brake System
Corrado, Jetta, Passat
DESCRIPTION
All models use a Teves Anti-Lock Brake System (ABS). See
Fig. 1. This system reduces the chance of wheel lock-up during heavy
braking. The system consists of 4 wheel speed sensors, Electronic
Control Unit (ECU), hydraulic modulator/pump and solenoid valves,
ANTI-LOCK warning light and BRAKE warning light. There are 2 relays
located at fuse/relay panel, to protect the hydraulic modulator and
ECU.
NOTE: For more information on brake system, see appropriate BRAKE
SYSTEM article.
OPERATION
When pressure is applied to brake pedal, the ECU monitors
input signals from each wheel speed sensor. If ECU measures a rate of
reduction greater than what is programmed in ECU, the ECU will output
a signal to appropriate solenoid valve. Each solenoid valve allows
hydraulic pressure to increase or decrease to the appropriate wheel
cylinder.
If a system failure occurs, the ANTI-LOCK warning light,
located on instrument panel, will come on. System will be deactivated,
but conventional brake system will still operate. If brake fluid level
drops too low, BRAKE warning light, located on instrument panel, will
come on.
ANTI-LOCK BRAKE SAFETY PRECAUTIONS
* NEVER open a bleeder valve or loosen a hydraulic line while
ABS is pressurized,
* NEVER disconnect or reconnect any electrical connectors while
ignition is on. Damage to ABS control unit may result.
* Only use specially designed brake hoses/lines on ABS equipped
vehicles.
* DO NOT tap on speed sensor components (sensor, sensor rings).
Speed rings must be pressed, NOT hammered into hubs. Striking
these components can cause demagnetization or a loss of
polarization, affecting the accuracy of the speed signal
returning to the ABS control unit.
* DO NOT mix tire sizes. Increasing the width, as long as tires
remain close to the original diameter, is acceptable. Rolling
diameter must be identical for all 4 tires (and spare tire
also). Some manufacturers recommend tires of the same brand,

ANTI-LOCK BRAKE SYSTEM
Article Text (p. 2)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:42PM
style and type. Failure to follow this precaution may cause
inaccurate wheel speed readings.
* DO NOT contaminate speed sensor components with grease. Only
use recommended anti-corrosion coating.
* When speed sensor components have been removed, ALWAYS check
sensor-to-ring gap when applicable. These specifications can
be found in WHEEL SPEED SENSOR under ADJUSTMENTS.
* ONLY use recommended brake fluids. DO NOT use silicone brake
fluids in an ABS equipped vehicle.
* When installing transmitting devices (CB's, telephones, ect.)
on ABS equipped vehicles, DO NOT locate antenna near the ABS
control unit or any control unit.
* Disconnect all on-board computers when using electric welding
equipment.
* DO NOT expose the ABS control unit to prolonged periods of
high heat (185øF/85øC for 2 hours is generally considered a
maximum limit).
CAUTION: The ABS system is under extremely high pressure.
Depressurize the brake system before loosening or removing
any hydraulic component.
DEPRESSURIZING BRAKE SYSTEM
Turn ignition off. Depress and release brake pedal 25-35
times, or until there is a noticeable increase in the effort to
depress the brake pedal. Do not turn ignition on until all hydraulic
lines and components are fully tighten.
BLEEDING BRAKE SYSTEM
FRONT BRAKES
Depressurize brake system. See DEPRESSURIZING BRAKE SYSTEM.
Connect a container with hose to left front bleeder screw. Have
assistant depress and release brake pedal a few times. Holding brake
pedal down, open bleeder screw and allow fluid to enter container.
Close bleeder screw and then release brake pedal. Continue this method
until no air is present in fluid. Check master cylinder fluid level to
make sure it does not go below minimum level mark. Use same procedure
for right front brake.
REAR BRAKES
CAUTION: When bleeding rear brakes, accumulator pressure (about 3100
psi) is used to assist in procedure. Use eye protection
when performing this procedure. DO NOT allow pump to run
longer than 2 minutes. See ANTI-LOCK BRAKE SAFETY
PRECAUTIONS in this article.
Attach hose and container to right rear bleeder screw.
Position actuator lever on load-sensing pressure regulator toward rear

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. 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

ELECTRICAL COMPONENT LOCATOR
Article Text (p. 29)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:44PM
Wheel Speed Sensor Mounted near hub assembly.ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ SOLENOIDS & SOLENOID VALVES
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄComponent Component Location
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄIdle Stabilizer Valve Across from throttle valve,
near valve cover.
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ SWITCHES
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄComponent Component Location
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄA/C Pressure Switch In refrigerant line, near left
side of condenser.
Anti-Lock Brake (ABS) Pressure
Warning Switch Mounted in hydraulic modulator
below brake fluid reservoir.
Back-Up Light Switch Mounted near gear selector on
transmission.
Brake Fluid Level Switch In cap on brake fluid
reservoir.