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Sensor Adjustment & Component Testing

How to Test Wheel Speed Sensors

NOTE

At initial installation, no gap must exist between the sensor and the tooth wheel.

After you install a hub, always check that the sensor is adjusted properly.

Operating the trailer can cause a gap to develop between the

sensor and the tooth wheel.

If the gap exceeds 0.040-inch, the system may not function correctly.

To adjust the sensor, twist and push the sensor through the

sensor bracket as far as possible

or until the sensor touches the tooth wheel.

Sensor Test Procedure

1. Disconnect power to the ECU/Valve Assembly.

2. Disconnect the sensor electrical connector from the ECU/Valve

Assembly.

3. Connect the Volt/Ohm meter leads to the two wire component

terminals

inside the disconnected connector.

4. When checking the resistance, the meter must read 50-2000 ohms.

5. Check and replace the sensor and cables as required.

6. Repeat Steps 1-5 for each sensor in the system.

Sensor Output Voltage Test

1. Disconnect power from the ECU/Valve Assembly.

2. Connect the AC Volt/Ohm meter leads to the sensor terminals

inside the connector.

3. Rotate the corresponding wheel at a constant speed of

one-half revolution per second.

4. The output voltage must be greater than 0.2 volts AC.

5. When there is no reading:

a. Trace the cable to verify that the cable

connects to the wheel you turned.

b. Check that you turned the correct wheel.

c. Check that the system is wired correctly.

d. Check that the sensor touches the tooth wheel.

6. If the Volt/Ohm meter still indicates no reading or a low reading

after following the above procedures, check and replace the component

and cables as required.

7. Repeat Steps 1-5 for each sensor in the system.

Check ABS Functions

· Meritor WABCO recommends that you test a vehicle's ABS

after a new installation and after you diagnose, repair and

erase faults in the ABS.

· Perform installation tests and blink code diagnostics using the

blink code diagnostic tool or the MPSI Pro-Link® 9000

(Meritor WABCO Cartridge Model J 38500-404, version 4.0 or higher).

ABS External Modulator Valve

Measure resistance across each valve solenoid coil

terminal and ground on the ABS valve to ensure 4.0 to 8.0 ohms.

Valve and cable pinouts are illustrated in Figure 7.1.

Figure 7.1

· To check the cable and the ABS valve as one unit, measure resistance

         across the pins on the ECU connector of the harness. See Figure 7.2.

- For 2S/1M, 2S/2M, and 2S/4M systems, measure the resistance

    across pins 1 and 3 and pins 2 and 3.

- For 4S/3M systems ("Y" cable connectors), measure across

    pins 3 and 4 and pins 3 and 5.

- Resistance should be between 4.0 and 8.0 ohms for

    each measurement. Figure 7.2.

Figure 7.2

· If the resistance is greater than 8.0 ohms clean the electrical contacts

in the solenoid. Check the resistance again.

Final Test Before Returning a Trailer to Service

For ECU/Valve Assembly Part Number 472 500 011 0

(without external diagnostic connector)

NOTE

If you are testing ECU 472 500 001 0, contact the

Meritor WABCO Customer Support Center

at 800-535-5560.

ABS Electrical/Hardware Installation Test

1. Provide 12 volts DC power (9.5-14 volts is an acceptable range)

to the ECU/Valve Assembly.

- Suggested power source: 12-volt battery.

2. Observe the ABS warning lamp and the blink code lamp on the ECU.

Check the results in Table F.

Table F - ECU Part Number 472 500 011 0

If	Status	Action
Trailer ABS warning lamp does not come ON. OR Blink code lamp on ECU does not come ON.	Minimum power requirement not met or wiring problem exists.	Check electrical connections and power source. Make necessary repairs.
Trailer ABS warning lamp comes ON. AND Blink code lamp on ECU continues to flash	Hardware fault code	Identify fault location. Make necessary repairs to the installation: # Blinks Location Sensor YEl (curbside) Sensor YE2 (roadside) ECU/Valve Assembly Power Supply 15 ECU Failure
Trailer ABS warning lamp comes ON and stays ON. AND ECU clicks twice. AND Blink code lamp on FCU comes ON briefly, then goes OFF.	Proper hardware installation	Perform Sensor Installation Test
Trailer ABS warning lamp comes ON for 3 seconds, then goes OFF. AND ECU clicks twice. AND Blink code lamp on ECU comes ON briefly, then goes OFF.	Proper hardware installation. Proper sensor installation.	None required

ABS Sensor Installation Test (ECU Part Number 472 500 011 0)

1. Remove power.

2. Raise both sensed wheels off of the ground.

Apply air to emergency line to fill air tanks and release parking brake.

3. Provide 12 volts DC power (9.5-14 volts is an acceptable range) to ECU/Valve Assembly.

(Make sure trailer ABS warning lamp and ECU blink code lamp operate correctly,

as described in "ABS Electrical/Hardware Installation Test".)

4. Rotate the sensed wheels - ONE AT A TIME -at a rate of 1/2 revolution per second.

5. Check Table G - Sensor Installation Test,

"Sensor Installation Test."

Table G - Sensor Installation Test

If Status Action

Trailer ABS warning lamp goes OFF. ECU senses proper speed.Sensors properly installed. No further testing required.

Trailer ABS warning lamp does not go OFF.
AND

There is no blink code flashing on ECU.
There is a sensor gap problem.
Adjust sensor gap. Push sensor into its holder until it contacts the tooth wheel.

Measure the AC voltage output.

Value should be 0.2 volts AC when

wheel is rotated at a rate of 1/2

revolution per second.

Make necessary repairs.

Trailer ABS warning lamp does not go OFF.

AND

Blink code is on and flashing on the ECU.

System fault exists. Count the number of flashes. This is the blink code.
Using Table H - Blink Code Table, identify the blink code. Make necessary repairs.

Table H - Blink Code Table

Blink

Code

Problem

Area

Action

4

Sensor YE1 (curbside sensor)

Check sensor installation. Make necessary repairs.

6

Sensor YE2 (roadside sensor)

Check sensor installation. Make necessary repairs.

10

ECU/Valve Assembly

Verify proper installation. If blink code continues, contact Meritor WABCO for assistance.

14

Power Supply

Verify proper electrical installation. Check power supply. Make necessary corrections.

15

ECU Failure

Verify proper installation. If code continues, contact Meritor WABCO for assistance.

After making the necessary corrections, repeat the sensor installation

test to verify proper sensor installation.

For ECU/Valve Assembly Part Numbers 472 500 012 0 and

S 472 500 013 0

(Units with External Diagnostic Connector)

NOTE

If you are testing ECU Part Number 472 500 001 0, contact the Meritor WABCO

Customer Support Center at 800-535-5560.

ABS Electrical/Hardware Installation Test

Provide 12 volts DC (9.5-14 volts is an acceptable range) to the ECU/Valve Assembly. Suggested power source: 12-volt battery.

Observe the ABS warning lamp and the blink code lamp on the ECU. Check the results in Table I.

Table I

If

Status

Action

Trailer ABS warning lamp does not come ON. OR

Blink code lamp on ECU does not come ON.

Minimum power requirement not met or wiring problem exists.

Check electrical connections and power source. Make necessary repairs.

Trailer ABS warning lamp comes ON. AND

Blink code lamp on ECU continues to flash.

Hardware fault code.

Identify fault location. Make necessary repairs to the installation:

# Blinks Location

3 Sensor BU1

4 Sensor YE1

5 Sensor BU2

6 Sensor YE2

7 External Modulator (Red) 4S/3M only

9 External Modulator (BU)

10 ECU Modulator (YE)

14 System Configuration or Power Supply

15 ECU (contact Meritor WABCO)

Trailer ABS warning lamp comes ON and stays ON.

AND

ECU clicks twice.

AND

Blink code lamp on ECU comes ON briefly then goes OFF or flashes 14 times, then goes out.

Proper hardware installation.

Perform Sensor Installation Test.

Trailer ABS warning lamp comes ON for 3 seconds, then goes OFF.

AND

ECU clicks twice.

AND

Blink code lamp on ECU comes ON briefly, then goes OFF.

Proper hardware installation. Proper sensor installation.

None required.

Sensor Installation Test (ECU Part Numbers 472 500 012 and 472 500 013 0)

Purpose of Test: To verify proper sensor gap, sensor hook-up to the ECU,

ABS valve operation, and pneumatic plumbing connections of the

Meritor WABCO Easy-Stop™ ABS on a new trailer.

1. Remove power from the ABS.

2. Raise sensed wheels so that they may be rotated.

3. Go to the diagnostic tool. Reapply power to the ABS.

· If there is no diagnostic tool on the trailer, temporarily

install one for this test. You must use a diagnostic tool ------

to complete the Sensor Installation Test.

4. Check the diagnostic tool to verify the status of the yellow LED. Figure 7.3.

· If LED comes ON and stays ON, go to Step 5.

· If LED does not light, verify adequate power is applied to the system.

Make the necessary repairs.

Figure 7.3

5. Press and release the blink code switch three times for Sensor Installation

        Test Mode, one second each time, separated by a release time of one second.

· The LED should display eight rapid flashes. This indicates the Sensor

Installation Test Mode. Then, the LED will continuously display the

system configuration code:

-2 Flashes = 4S/3M

-3 Flashes = 4S/2M

-4 Flashes = 2S/2M

-5 Flashes = 2S/1M

· If this does not occur, repeat Step 4.

· Attach the emergency and control air lines to the trailer.

    Fill air tanks to release the spring brakes.

6. Rotate each sensed wheel - ONE AT A TIME -at a rate of 1/2 revolution

    per second. Apply control pressure to activate the brakes. Refer to Figure 7.4.

Figure 7.4

7. Observe the automatic slack adjuster on the rotated wheel. It must move

in and out as the ABS valve cycles. This indicates a proper installation.

· If the slack adjuster on the rotated wheel does not move -

    but the slack adjuster on the opposite wheel does move -

    the sensor leads are reversed or the air line is plumbed wrong.

    Correct the installation.

· If the slack adjuster on the rotated wheel does not move,

    there may be a sensor gap problem. Check the sensor gap and make

    the necessary repairs.

8. Repeat Steps 6 and 7 on the remaining sensed wheels.

9. If you installed a diagnostic blink code tool for this test, remove it.

     Replace the protective cap over the connector.

Trailer Identification

An Easy-Stop™ Trailer ABS warning label is generally affixed to the trailer near the

ABS trailer warning lamp.

If this label is not on the trailer, let your supervisor know.

Labels are available from Meritor WABCO. Ask for Part Number TP-95172.

For additional assistance, contact the Meritor Customer Support Center at 800-535-5560.

Before calling the Meritor Customer Support Center, be prepared to provide

the following information about the trailer you are working on:

1. Trailer make and model year.

2. What is the symptom/complaint? What is the component doing or not doing?

3. What is the ABS blink code or MPSI Pro-Link® 9000 reading?

4. Have any resistance and/or voltage measurements been taken?

5. What is the result of visual inspection of connectors, harness and components?

6. When does the symptom occur (vehicle moving, compressor unloading, etc.)?

7. Does the trailer have any unusual characteristics

    (for example, mismatched tires or larger than normal air consumption)?

8. Were maintenance manuals available? If so, which ones were used?

9. What is the part number of the ECU/Valve Assembly? What is the system configuration?

By having the above information ready when you call, your

customer support technician will be better equipped to assist you.

Meritor Customer Support Center, 800-535-5560

Copyright © 2000 Ranco Trailers