Ford F150 Pickup. Instruction — part 361

Fig. 2: Torque Specifications (2 Of 2)
Courtesy of FORD MOTOR CO.

DESCRIPTION & OPERATION

ANTI-LOCK CONTROL

The Rear Anti-Lock Brake System (RABS) consists of the following components:

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Anti-lock brake control module (2C018)

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Rear Anti-Lock Brake System (RABS) valve (2B373)

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Rear anti-lock brake sensor (2L373)

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Rear anti-lock brake sensor indicator (2C189)

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RABS warning indicator

DIAGNOSIS & TESTING

ANTI-LOCK CONTROL

Refer to ANTI-LOCK BRAKES .

Special Tool(s)

2003 Ford Pickup F150

2003 BRAKES Anti-Lock Control-Rear - F150 Pickup

Fig. 3: Identifying Anti-Lock Control Special Tool
Courtesy of FORD MOTOR CO.

Principles Of Operation

The anti-lock brake control module carries out system tests during start-up and normal operation. The RABS
valve, rear anti-lock brake sensor (2L373), and fluid level circuits are monitored for proper operation. If a
concern is found, the anti-lock brake control module deactivates and the Yellow ABS warning indicator
illuminates.

Most concerns cause the Yellow ABS warning indicator to stay illuminated until the ignition is turned OFF, at
which time the anti-lock brake control module retains the Diagnostic Trouble Code (DTC) in memory (also
referred to as Keep Alive Memory or KAM). At any time while the ignition is turned on, a DTC may be
obtained. DTC 16 indicates that the system is operating normally. However, those concerns associated with loss
of power to the anti-lock brake control module cause the system to be deactivated and the Yellow ABS warning
indicator to be illuminated, but do not cause a DTC.

The Brake Pedal Position (BPP) switch, when activated, signals the anti-lock brake control module that a
braking condition is occurring.

The Rear Anti-Lock Brake System (RABS) continuously monitors rear wheel speed with a rear anti-lock brake
sensor. When the teeth on the rear anti-lock brake sensor indicator, pass the RABS sensor pole piece, an AC
voltage is induced in the sensor circuit with a frequency proportional to the average rear wheel speed. In the
event of an impending lockup during braking, at vehicle speeds above approximately 8 km/h (5 MPH), the anti-
lock brake control module senses the drop in rear wheel speed. If the rate of deceleration is excessive, the anti-
lock brake control module activates the RABS valve, causing the isolation valve to close. With the isolation
valve closed, the rear wheel cylinders (2261) are isolated from the brake master cylinder (2140) and the rear
brake fluid pressure cannot increase. If the rate of deceleration is still excessive, the anti-lock brake control
module will energize the dump solenoid with a series of rapid pulses to bleed the rear brake caliper fluid into an
accumulator built into the RABS valve. This reduces the brake fluid pressure to the rear brake caliper and

2003 Ford Pickup F150

2003 BRAKES Anti-Lock Control-Rear - F150 Pickup

allows the rear wheels to spin at vehicle speed. The anti-lock brake control module pulses the dump and
isolation solenoids in a manner that will keep the rear wheels rotating while still maintaining rapid deceleration
during braking.

Once stopped, the operator releases the brake pedal (2455), the isolation valve de-energizes and any fluid in the
accumulator returns to the brake master cylinder. Normal brake operation resumes.

Inspection & Verification

1. Verify the customer concern by applying brakes under different conditions.

2. Visually inspect for obvious signs of mechanical and electrical damage. Refer to the following chart:

Fig. 4: Visual Inspection Chart
Courtesy of FORD MOTOR CO.

3. If the fault is not visually evident, verify the symptom and proceed to Self Test.

NOTE:

Ensure the integrity of all connectors and their associated harnesses.

2003 Ford Pickup F150

2003 BRAKES Anti-Lock Control-Rear - F150 Pickup

System Pre-Check

The system pre-check screens a vehicle for relatively simple diagnostic repairs, such as loose connectors, blown
fuses, etc. However, the system pre-check also prepares the vehicle for further diagnostics. In addition, warning
indicator concerns are diagnosed in this system pre-check.

The RABS module uses the Yellow ABS warning indicator and under some conditions the Red brake warning
indicator to alert the driver to a system malfunction. Both lights must be working properly to assist in diagnosis.
The steps below must be followed prior to beginning the RABS diagnostic procedure.

Vehicle Setup

For 4WD vehicles, shift into 2WD. Drive the vehicle to a level area, and place the shift lever in PARK for
automatic transmissions (7003) and NEUTRAL for instruction transmissions. Turn the ignition off, set the parking
brake, and turn on the running lamps. Place blocks behind the rear wheels and in front of the front wheels.
Release the parking brake.

Warning Indicator Lamp

The Red BRAKE warning indicator is constantly monitored by the anti-lock brake control module. If the Red
BRAKE warning indicator illuminates, the anti-lock brake control module will disable the RABS system and
turn on the Yellow ABS warning indicator. For this reason, diagnosing and resolving any base brake concerns
illuminating the Red BRAKE warning indicator will, in most cases, resolve a perceived RABS concern.

Warning Indicator Self-Check

The Red BRAKE warning indicator is used to indicate a low fluid level condition or parking brake applied
condition. To check this light, insert the key in the ignition switch (11572) and turn it to the START position.
The warning indicator should illuminate in this position. If the Red brake warning indicator fails to illuminate,
go to the SYMPTOM CHART .

Allow the key to spring back from the START position to the RUN position. At this time, the Red BRAKE
warning indicator should turn off. If it does not turn off, recheck the parking brake switch to make sure that it is
fully disengaged. In the event that the Red BRAKE warning indicator remains on, go to the SYMPTOM
CHART .

Yellow ABS Warning Indicator

The Yellow ABS warning indicator is used to indicate a malfunction and a deactivation of the RABS system.
To check this indicator, first follow the procedure for Red BRAKE Warning Indicator Self-Check, and allow

NOTE:

Carry out this procedure first. Failure to do so may result in incorrect diagnosis
of the problem and improper replacement of components.

WARNING:

Place blocks behind the rear wheels (1007) and in front of the front
wheels to prevent the vehicle from moving while the system pre-check is
being done.

2003 Ford Pickup F150

2003 BRAKES Anti-Lock Control-Rear - F150 Pickup