When your ABS and brake lights illuminate simultaneously, this indicates an urgent
problem in your braking system that poses serious danger while driving. This could
be caused by faulty sensors, blown fuses or another issue with your vehicle’s wiring.
To address this, first reset your ABS and brake warning lights by switching your
ignition on, disconnecting power for several minutes, and reconnecting.
Check Brake Fluid Levels
Normal wear-and-tear effects of wearing brake pads will lead to some decreases in
brake fluid levels; if they drop too low, however, an ABS controller could become
confused and activate an indicator light. To check this properly, view your reservoir
closely – most should feature a scale with minimum and maximum marks – the fluid
should ideally fall near or be within these marks.
An ABS indicator lamp may also be activated by a malfunctioning wheel speed
sensor. These sensors inform the ABS controller about how fast each wheel is
turning, which allows them to control power allocation accordingly. When these
sensors become dirty or defective, however, their ability to relay this data is
compromised and thus it cannot reach the computer for processing.
Sensors may also become damaged by air in the hydraulic system, which could be
the result of either an electronic component not functioning as intended or using
improper type of brake fluid. If this occurs, drain and refill with proper DOT 3 or DOT
4 fluid.
Check the ABS Sensor
Most modern cars contain sensors on each wheel that send signals to an ABS
computer to indicate whether or not a wheel has lost traction and needs braking, or
can gauge how quickly a car is slowing. When one fails, its ABS light illuminates, as
well as sometimes also lighting up other indicators like stability control lights or
traction control indicators.
First, disconnecting the battery. Next, using jack and jack stands, raise your vehicle
while simultaneously applying parking brakes. Remove electrical connector from
ABS sensor harness. Unbolt sensor from mounting bracket if applicable and
disconnect retaining bolt. Test continuity using multimeter in the 20k Ohms range; if
all seems well replace sensor and install new harness connector. Reconnect ABS
sensor before lowering vehicle and clear any diagnostic codes related to ABS with
scan tool.
Check the ABS Module
When your ABS light comes on, it indicates a problem with reading wheel speed
sensors. As soon as this occurs, check both its fuse (which could be located either in
the engine bay or passenger compartment), as well as conducting a visual
inspection of its unit itself. Furthermore, consult a repair manual for more
information regarding how your ABS module functions.
If the fuse appears to be functional and unplugging and replugging the main harness
does not dim the light, it may be time to use a multimeter to measure voltages and
resistance values on sensor connections. Since some signals on these wires only
require millivolts of voltage for transmission, even small amounts of resistance can
prevent their signals from reaching their destination.
If the sensors cannot pinpoint any issues, you can also use an ABS controller scanner
to scan for fault codes that will reveal whether the problem lies with one of them or
with the ABS module itself. This will give a much clearer idea as to where exactly to
begin your investigation.
Check the Wiring
Whenever the ABS light illuminates in your F-150 while driving, this indicates a
malfunction with its anti-lock braking system. Often this is caused by a defective
sensor not providing accurate speed information to the ABS control unit or when the
hydraulic component of an ABS pump malfunctions and causes brake pressure levels
in certain wheels to drop – both situations which are potentially dangerous when
driving on steep or winding roads.
Check and replace the fuse in your ABS system as necessary. Fuses regulate
electrical circuits, so if one becomes blown it could have detrimental effects on its
performance. Make sure to purchase one with an amp rating appropriate to avoid
damage to other components; once this step has been accomplished you can
proceed to inspect other aspects of your ABS system.