DTC light keeps coming on and applying my brakes when driving slow and in a straight line, is it expensive to fix?

Stop Lamps
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). Ground for the right rear stop lamp and CHMSL is applied at G402. Ground for the left rear stop lamp is applied at G400. The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.

Do you know what DTC'S - diagnostic trouble codes are ?
DTC B3903 02: Stop Lamp Relay Circuit Short to Ground
DTC B3903 05: Stop Lamp Relay Circuit Open or Short to Voltage

DTC C0277 06: Brake Pedal Position Sensor Circuit Short to Ground or Open
DTC C0277 07 : Brake Pedal Position Sensor Circuit Voltage Above Threshold
DTC C0277 09 : Brake Pedal Position Sensor Circuit Rate of Change Above Threshold
DTC C0278 00: Brake Pedal Position Sensor Not Calibrated
DTC C0870 03 : Device Voltage Reference Output 1 Circuit Voltage Below Threshold
DTC C0870 07 : Device Voltage Reference Output 1 Circuit Voltage Above Threshold

Your best bet mite be to take it to a qulaified repair shop .

ABS code not check engine light code .
DTC C0201 00: Antilock Brake System (ABS) Enable Relay Contact Circuit
The solenoid relay, located within the electronic brake control module (EBCM), supplies battery voltage to all of the valve solenoids.
Circuit/System Verification
With scan tool installed, clear the DTCs then drive the vehicle in a straight line at a speed greater than 20 km/h (13 mph). If the DTC did not set as a current DTC see diagnostic aids.
Circuit/System Testing
Test for an open or a short to ground in the battery positive voltage circuit to the EBCM. Verify no open or a short to ground is found.
Test the EBCM ground circuit, an open or high resistance.
? If an open or a short to ground is found, repair the circuit.
Replace the EBCM assembly.

DTC C0201 (Equal to or over 8600 GVW)
The system relay, located within the electronic brake control module (EBCM), supplies battery voltage to all of the valve solenoids and to the Antilock Brake System (ABS) pump motor. When the relay contacts close, the EBCM monitors the voltage supplied to the valve solenoids and compares this voltage to monitored ignition voltage.
Action Taken When the DTC Sets
• The EBCM disables the ABS/DRP.
• The ABS indicator turns ON.
• The brake warning indicator turns ON

What's wrong with it ? Need more info . Light on ? The first thing to do would be to have the vehicle checked for DTC'S - diagnostic trouble codes ! Get a diagnostic direction , not just replacing parts . Need a professional grade scan tool . Plus reading how stabilitrak works would also be a good Idea . StabiliTrak General Motors Stability Control

Vehicle Stability Enhancement System (VSES)
The vehicle stability enhancement system (VSES) adds an additional level of vehicle control to the electronic brake control module (EBCM).
Yaw rate is the rate of rotation about the vehicle's vertical axis. The lateral accelerometer measures the sideways acceleration of the vehicle. The VSES is activated when the EBCM determines that the desired yaw rate and lateral forces do not match the actual attitude of the vehicle.
The desired attitude of the vehicle are calculated from the following inputs:
• The position of the steering wheel
• The speed of the vehicle
• The lateral, or sideways acceleration of the vehicle
• Yaw rate of the vehicle
• Master cylinder brake pressure
The difference between the desired yaw rate and the actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM attempts to correct the vehicle's yaw motion by applying differential braking to the appropriate wheel. The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error.
The VSES activations generally occur during aggressive driving, in turns, or on poor road conditions, without much use of the accelerator pedal. When braking during VSES activation, the pedal pulsations feel different than the ABS pedal pulsations. The brake pedal pulsates at a higher frequency during VSES activation.

There a number of DTC'S that can set .
DTC C0035-C0050
DTC C0110
DTC C0131
DTC C0161
DTC C0179
DTC C0186
DTC C0196
DTC C0201
DTC C0242 or P0856
DTC C0245
DTC C0292
DTC C0558
DTC C0561
DTC C0563
DTC C0710

Do you know what DTC'S are , and a diagnostic flow chart ?

1. I would not be concerned because if there was a failure in the ABS you would definitely get an ABS warning light and the ABS and most likely the stability control/traction control systems (with added warning lights) will all switch off .

2. You can test if the ABS is operational. On a very quiet damp surface, straight, wide road( with NO other cars around), apply your brakes hard from a very low speed - up to 20 mph ONLY driving in a straight line - until the car stops. The front brakes should attempt to lock up under hard braking and if the ABS is operational you will feel it kick in and the brake pedal will pulsate as the ABS constantly allows brake pressure and then releases it to prevent the wheels from locking up on the damp road. If the ABS does not kick in be ready to release the brake pedal quickly to allow the wheels to rotate so you can steer the car safely. Without the ABS the front wheels should begin to lock up on the damp road surface due to the low level of tire grip. ONLY test this at very low speed and ONLY when driving in a straight line on a straight section of wide road with no other vehicles around.

Have you checked the master cylinder for leaks and around the brake booster? You may have a bad brake light switch.

ABS on ? DTC'S - diagnostic trouble code's are probably stored in the ABS control module . 4X4 an ABS are not related . To fix , take it to a qualified repair shop.
SERVICE 4WD: Refer to Transfer Case Circuit Description in

Transfer Case Shift Control Module
The transfer case shift control module uses the VIN information for calculations that are required for the different calibrations used based on axle ratio, transmission, tire size, and engine. The system does not know which calibration to use without this information. The transfer case shift control module monitors the speed of the front and rear propshafts in order to detect wheel slippage. When wheel slippage is detected, the module applies a clutch pack contained in side the transfer case. This clutch pack is used to lock-in and apply the front propshaft, transferring torque to the front wheels. The clutch pack is applied by a motor/encoder assembly. When slip is no longer detected by the transfer case shift control module, the clutch is no longer applied.

These are all code's for 4X4 Do you know what a DTC is ? diagnostic trouble code
DTC B0770
DTC B0775
DTC B0780
DTC B0785
DTC B0790
DTC B2725
DTC C0300
DTC C0305
DTC C0306
DTC C0321
DTC C0327
DTC C0359
DTC C0374
DTC C0379
DTC C0550

ABS DTC'S
DTC C0221-C0227 or C021
DTC C0229 or C029
DTC C0235-C0237, C035-C037, or P1504
DTC C0238 or C038
DTC C0241-C0254 or C041-C054
DTC C0265 or C0266 and C065 or C066
DTC C0267 or C0268 and C067 or C068
DTC C0269 or C0274 and C069 or C074
DTC C0271-C0273, C0284
DTC C0279
DTC C0281 or C081
DTC C0283 (w/NW7)
DTC C0287, P1644, or P1689
DTC C0290 or C0292
DTC C0291
DTC C0297
DTC C0298 or P1571

bleed the system, this is a sign of air somewhere in the lines bleeding is the easiest and least expensive option to try first.

The "pulsating" you refer to is Normal for a vehicle with ABS (Anti-Lock Brake Systems). It keeps the vehicle braking in a straight line and monitors each wheel with a sensor as to how fast it's turning while braking. The "pulsations" you feel is the ABS Computer turning each individual brake on and off to prevent a lock-up or skid. Perhaps if you road test the vehicle and apply your brakes lightly as in coming up on a stop sign in a residential neighborhood, you'll feel what you consider to be, "normal braking." Pulsations usually come at higher speeds and as to how much pressure you're putting on the brake pedal. You're safer than most now knowing that braking, even in snow, rain or gravel, that your vehicle will stop in a straight line instead of sliding to one side or the other.

If unhappy with ABS Braking, you can always remove the fuse to the ABS computer rendering it inoperative, so you have both choices as to what you'd like to do, right here.

I hope this helps,

~00 Buck~

"Still Living on the Right Side of Dirt..."

If the brake warning light comes on when you apply the brakes, or is on continuously, it means that hydraulic pressure has been lost in one side of the brake system or that the fluid level in the master cylinder is dangerously low (due to a leak somewhere in the brake system). In either case, the fluid level in the master cylinder should be checked. Adding brake fluid to the master cylinder reservoir may temporarily solve the problem. But if there's a leak, the new fluid will soon be lost and the warning light will come back on.
Brake fluid leaks are serious because they may cause the brakes to fail! So avoid driving the vehicle until the system can be inspected to determine what's wrong. Leaks can occur in brake hoses, brake lines, disc brake calipers, drum brake wheel cylinders or the master cylinder itself. Wet spots at hose or line connections would indicate a leak that needs to be fixed.
Leaking brake fluid can also contaminate the brake linings, causing them to slip or grab. The uneven braking action that results may cause the vehicle to veer to one side when the brakes are applied. Brake shoes or pads that have been contaminated with brake fluid cannot be dried out and must be replaced.

go to ford dealership and have them scan your truck with a scan tool