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MERITORWABCO           TABLE OF CONTENTS

Section 6

Component Replacement

WARNINGS

! To prevent serious eye injury, always wear safe eye protection when you perform 

vehicle maintenance or service.

! Block the wheels to prevent the vehicle from moving. Support the vehicle with safety stands. 

Do not work under a vehicle supported only by Jacks. Jacks can slip and fall over. 

Serious personal injury can result.

! The ABS is an electrical system. When you work on the ABS, take the same precautions

 that you must take with any electrical system to avoid serious personal injury. 

As with any electrical system, the danger of electrical shock or sparks exists that can 

ignite flammable substances. You must always disconnect the battery ground cable before 

working on the electrical system.

NOTE

Disconnect power from the ECU/VaIve Assembly before you remove any components. 

Failure to disconnect power from the ECU can cause faults to be recorded and stored in ECU memory.

! CAUTION

Use the following procedures to avoid damage to the electrical system and ABS components.

When welding on an ABS-equipped vehicle it is necessary, disconnect the 

power connector from the ECU.

Wheel Speed Sensor

How to Remove a Sensor

    1. Follow the vehicle manufacturer’s instructions to back off the slack 

      adjuster and remove the tire, wheel and drum.

       
    2. Hold the sensor, not the cable, and use a twisting motion to 

      pull the sensor out of its mounting block.

       
    3. Remove the spring clip from the mounting block.
    4. Remove any fasteners that hold the sensor cable to other components.
    5. Disconnect the sensor cable from the extension cable.

How to Install a Sensor

Sensor locations vary according to suspension types. Typically, a spring suspension

 has sensors on the forward axle, and an air suspension has sensors on the rear axle.

  1. Apply a mineral oil-based grease that contains molydisulfide to the sensor spring clip and to the body of the sensor. The grease must be anti-corrosive and contain adhesive properties that will continuously      endure temperatures from –40º to 300ºF (-40º to 150ºC).
  2. Push the spring clip into the sensor holder from the inboard side, until the spring clip tabs are against the sensor holder. Push the sensor into the spring clip as far as possible. Refer to Figure 6.1.
  3. Route the sensor cable toward the brake chamber, over the brake spider, and behind the axle. Secure the cable to the axle between the brake spider and the suspension brackets. Continue to route the sensor cable behind the spring seats. Secure the cable to the axle one inch from the molded sensor plug. Refer to Figure 6.2.

 

Figure 6.1

Figure 6.2

4. Install the wheel hub carefully, so that the tooth wheel pushes against the 

sensor as you adjust the wheel bearings. After installation there should be no gap 

between the sensor and the tooth wheel. During normal operation a gap

of 0.04-inch is allowable.

5. Sensor Output Voltage Test: Use a Volt/Ohm meter to check the 

AC output voltage of the sensors while rotating the wheel at approximately 

one-half revolution per second. Minimum output must be greater than 0.2 volts AC.

If minimum output is less than 0.2 volts AC, push the sensor toward the tooth wheel. 

Recheck the sensor output.

ABS Relay Valve

Figure 6.3

! WARNING

Release all pressure from the air system before you disconnect any components. 

Pressurized air can cause serious personal injury.

How to Remove a Standard ABS Relay Valve

  1. Release all pressure from the air system.
  2. Disconnect the cable from the valve.
  3. Attach labels to identify all of the air lines.
  4. Disconnect the air lines from the valve.
  5. Remove the mounting fasteners if the valve is not nipple-mounted

     directly to the air tank.

  6. Remove the valve.

How to Install a Standard ABS Relay Valve

! CAUTION

You must use Schedule 80 pipe nipple (3/4-inch NPT) to nipple-mount the 

ABS relay valve securely to the reinforced air tank to avoid possible serious

 personal injury and damage to components.
  1. Install the valve with two lock nuts and washers as required. Tighten the hex nuts to a torque of 18 lb-ft (24 N·m) or nipple-mount the valve directly to the air tank with Schedule 80 pipe nipple (3/4-inch NPT). Т
  2. Connect the air lines to the ports according to the labels installed when the air lines were disconnected.
  3. Connect the cable to the valve.
  4. Pressurize the brake system. Apply the brakes and verify there are no air leaks.

The ECU/Valve Assembly

! WARNING TABLE OF CONTENTS

Release all pressure from the air system before you disconnect any components.

 Pressurized air can cause serious personal injury.

! CAUTION

The ECU and valve assembly are sealed together as one unit. 

To ensure product integrity and avoid possible damage to the components, 

do not attempt to separate the ECU from the valve.

How to Remove the ECU/VaIve Assembly

1. Release all pressure from the air system.

2. Attach labels to identify all air lines.

3. Disconnect the air lines from the ECU/Valve Assembly.

4. Disconnect the power cable, diagnostic cable, additional relay valve cable (if used), and all sensor cables from the ECU/Valve Assembly. Refer to Figure 6.4.

5. Remove the ECU/Valve Assembly from its mounting location:

    1. Bracket-mounted: Loosen and remove the two mounting bolts and lock nuts that hold the assembly to the mounting bracket. Remove the assembly
    2. Nipple-mounted to Air Tank: Unscrew the assembly from the air tank.

6. If the assembly being replaced is under warranty, please return it to the trailer OEM for replacement.

How to Install the ECU/VaIve Assembly

NOTE

The ECU/VaIve Assembly is supplied with black protective caps on each sensor connector.

When a sensor cable is not plugged into a sensor connector the black cap 

must remain on the connector to protect it from dirt and contamination. See Figure 6.4.

Figure 6.4

Figure 6.5

! CAUTION

You must use a Schedule 80 pipe nipple (3/4 inch NPT) to nipple mount the ECU/Valve Assembly securely to the air tank to avoid possible serious personal injury and damage to components.

1. Attach the ECU/Valve Assembly to the vehicle:

  1. Bracket-mounted: Use two 3/8-inch Grade 8 bolts with prevailing torque nuts to attach the assembly to the mounting bracket. Tighten to 18 lb-ft (24 N·m). T

Plug unused supply port (Port 1). Refer to Figure 6.5.

 

b. Nipple-mounted to air tank: Attach the ECU/Valve Assembly to the air tank, using a Schedule 80 pipe nipple (3/4-inch NPT). Tighten securely with exhaust port facing down. Do not over tighten.

Plug unused supply port (Port 1). Refer to Figure 6.6.

 

 

Figure 6.6

2. Connect the air lines to the ports. Follow the label markers installed when the air lines were disconnected.

3. Connect the sensor cables, external relay valve cable (if used), diagnostic cable, and power cable to the ECU/Valve Assembly. Use the black protective connector caps included with the replacement assembly to cover unused cable connectors.

4. Test the installation using blink code diagnostics

5. Perform the "Final Test Before Returning A Trailer to Service" test in Section 7.

How to Install the Blink Code Diagnostic Tool into the SAE J1587 Diagnostic Connector

NOTE

The blink code switch and LED lamp are sealed against dust and contaminants. The red dust cap protects the switch and lamp during use but is not an integral part of the diagnostic tool.

1. Remove the gray protective cap from the SAE J1587 diagnostic connector. Figure 6.7.

a. Turn the cap counterclockwise.

b. Pull off the cap.

2. Install the diagnostic tool into the diagnostic connector.

a. Align the notch on the diagnostic tool with the notch on the diagnostic connector. Refer to Figure 6.8.

b. Push the diagnostic tool firmly into the connector. Refer to Figure 6.8

 

Figure 6.7

NOTE

You must replace the gray protective cap if you remove the diagnostic tool from the diagnostic connector. Dirt and contaminants can damage the connector.

c. Rotate the gray ring on the diagnostic tool to securely lock the diagnostic tool into the plug.

Figure 6.8

 

3. If the diagnostic tool will remain permanently installed into the connector:

a. Remove the protective cap and guide wire that are attached to the mounting bracket.

b. Attach the diagnostic tool and guide wire to the mounting bracket.

 

 
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