Ram B1500, B2500, B3500, 1999-2003

4-Wheel Anti-Lock Brake System (ABS)

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Bleeding the ABS System



ABS system bleeding requires conventional bleeding methods plus use of the DRB scan tool. The procedure involves performing a base brake bleeding, followed by use of the scan tool to cycle and bleed the HCU pump and solenoids. A second base brake bleeding procedure is then required to remove any air remaining in the system.

  1. Perform base brake bleeding. Refer to the appropriate section.
  2.  
  3. Connect the scan tool to the data link connector beneath the dashboard.
  4.  
  5. Select "Antilock Brakes" followed by "Miscellaneous", then "Bleed Brakes". Follow the instructions displayed until the unit displays "Test Complete", then disconnect the scan tool and proceed.
  6.  
  7. Perform a base brake bleeding a second time.
  8.  
  9. Top up the master cylinder.
  10.  

Description & Operation



The four-wheel Antilock Brake System (ABS) is designed to prevent wheel lock-up during braking under virtually any road surface conditions. This allows the driver to retain greater control of the vehicle during braking.

The major components of the system are:



Controller Antilock Brakes (CAB)
 
Hydraulic Control Unit (HCU)
 
Wheel speed sensors
 
ABS warning light
 

The four-wheel ABS has a three-channel design. The front brake antilock valve provides two-channel pressure control of the front brakes. Each front wheel brake unit is controlled separately. Two solenoid valves are used in each control channel.

The rear brake antilock valve controls the rear wheel brakes in tandem. The rear brake valve contains two solenoid valves.

The front and rear antilock valves contain electrically operated solenoid valves. The solenoid valves modulate brake fluid apply pressure during antilock braking. The antilock electronic module operates the valves.

The antilock electrical system is separate from other electrical circuits in the vehicle. A specially programmed electronic control module is used to operate the system components.

Some models have Electronic Brake Distribution (EBD) designed into the system which eliminates the combination/proportioning valve.

The ABS electronic control module monitors wheel speed sensor inputs continuously while the vehicle is in motion. The module will not activate the ABS system as long as sensor inputs indicate normal braking.



Click image to see an enlarged view

Fig. ABS schematic-typical

During normal braking, the master cylinder, power booster and wheel brakes units all function as they would in a vehicle without ABS. The solenoid valves are not activated.

The wheel speed sensors converts wheel speed into electrical signals. These signals are transmitted to the module for processing and determine wheel lock-up and deceleration rate. When a wheel speed sensor signal indicates the onset of wheel lock-up the ABS braking is activated.

The antilock system retards the lockup conditions by modulating fluid apply pressure to the wheel brake units. The pressure is modulated according to wheel speed, degree of lock-up and rate of deceleration. The solenoid valves are cycled continuously to modulate pressure. Solenoid cycle time in antilock mode can be measured in milliseconds.

Diagnosis & Testing



Diagnosis of base brake conditions, which are mechanical in nature, should be performed first. This includes brake noise, lack of power assist, parking brake, or vehicle vibration during normal braking.

The static and dynamic checks occur at ignition start up. During the dynamic check, the CAB briefly cycles the pump and solenoids to verify operation. An audible noise may be heard during this self-check.

If an ABS component exhibits a fault during initialization, the CAB illuminates the amber warning light and registers a fault code in the memory.



Click image to see an enlarged view

Fig. 4-wheel ABS DTC chart

Wheel Speed Sensor Rings (Toothed Rings)



Removal & Installation

The "tone wheel" works in conjunction with the front wheel speed sensors as part of the ABS. There is one on each wheel.

The tone wheel is located on the hub/bearing, on the axle outer stub shaft or inside the hub/bearing housing, depending on model and equipment.

This component is not serviceable or removable and if damaged, the assembly of which it is a part must be replaced.



Click image to see an enlarged view

Fig. The tone wheel is not replaceable by itself-2WD shown

  1. Remove the differential case from the axle housing.
  2.  
  3. Clamp the differential case in a soft-jaw vise.
  4.  
  5. Remove and discard the ring gear bolts.
  6.  
  7. Tap the ring gear off with a rawhide or plastic mallet.
  8.  
  9. Remove the exciter ring with a soft-faced hammer.
  10.  

To install:

  1. Be sure to align the exciter ring tab with the slot in the differential case.
  2.  
  3. Invert the differential case and start two ring gear bolts. This will provide case to ring gear bolt hole alignment.
  4.  
  5. Press the exciter ring onto the differential case using the ring gear as a pilot.
  6.  
  7. Install new ring gear bolts and tighten in a cross pattern as follows:

    For 8 1 / 4 in. axles, 75 ft. lbs. (102 Nm)
     
    For 9 1 / 4 in. axles, 115 ft. lbs. (157 Nm)
     
    For 248 and 267 RBI axles, 130 ft. lbs. (180 Nm)
     
    For 286 RBI axles, 220 ft. lbs. (300 Nm)
     

  8.  

Wheel Speed Sensors



Front Wheel Speed Sensors
Removal & Installation
2-Wheel Drive
  1. Raise and support the vehicle.
  2.  
  3. Remove the wheel.
  4.  
  5. Remove the brake caliper and rotor.
  6.  
  7. Remove the sensor attaching bolts.
  8.  
  9. Disconnect the wire and remove the sensor from the vehicle.
  10.  

To install:

  1. Tighten the bolts to 18 ft. lbs. (23 Nm).
  2.  


NOTE
Use the original or replacement sensor bolts only. The bolt is special and must not be substituted.



Click image to see an enlarged view

Fig. Front wheel sensor position: 1997-99 Ram 2WD

  1. Raise and support the vehicle.
  2.  
  3. Remove the sensor bolt from the steering knuckle and remove the sensor.
  4.  
  5. Disconnect the ABS wheel speed sensor wire and detach the wire from securing clips.
  6.  

To install:

  1. Tighten the sensor bolt to 17 ft. lbs. (23 Nm).
  2.  


NOTE
Use the original or replacement sensor bolt only. The bolt is special and must not be substituted.

  1. The remainder of the procedure is the reverse of removal.
  2.  



Click image to see an enlarged view

Fig. Front wheel sensor location-Dakota, Durango

4-Wheel Drive Models
  1. Raise and support the vehicle.
  2.  
  3. Remove the wheel.
  4.  
  5. Remove the brake caliper.
  6.  
  7. On 8-stud wheels, remove the rotor hub bearing assembly and separate the rotor from the hub bearing.
  8.  
  9. On other wheels, remove the rotor.
  10.  
  11. Remove the sensor attaching bolts.
  12.  
  13. Disconnect the wire and remove the sensor from the vehicle.
  14.  

To install:

  1. Tighten the bolts to 13 ft. lbs. (18 Nm).
  2.  


NOTE
Use the original or replacement sensor bolts only. The bolts are special and must not be substituted.

  1. The remainder of the procedure is the reverse of removal.
  2.  



Click image to see an enlarged view

Fig. Front wheel speed sensor installation-4WD

Rear Wheel Speed Sensors
Removal & Installation
  1. Raise the vehicle.
  2.  
  3. Remove the brake line mounting nut, if fitted, and remove the brake line from the sensor stud.
  4.  
  5. Remove the mounting stud from the sensor and shield.
  6.  
  7. Remove the sensor and shield from the differential housing.
  8.  
  9. Disconnect the wire and remove the sensor.
  10.  

To install:

  1. Connect harness to sensor. Be sure the seal is securely in place between the sensor and wiring connector.
  2.  
  3. Install O-ring on sensor if removed.
  4.  
  5. Install sensor on differential; housing, sensor shield, mounting stud. Tighten to 18 ft. lbs. (24 Nm).
  6.  
  7. Install the brake line on the sensor stud and install the nut.
  8.  


NOTE
Use the original or replacement sensor bolt only. The bolt is special and must not be substituted.

  1. Lower the vehicle.
  2.  

 
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