DSC comes on at highway speeds on dry pavement. Cruise disengages. Have to manually override with DTC button or it will slow the car to stop.

Your best bet , take your vehicle to a qualified repair shop that has a professional scan tool an service repair info . So it can be diagnosed correctly . The Stop lamp switch is not a old school conventional type . Has three wires , five volt ref. voltage from the BCM ,
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.

Checking for DTC's - diagnostic trouble code's in the BCM would be my first diagnostic step , not guessing an replacing parts .

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
As you can see a number of DTC'S can be set , so do yourself a favor an let a qualified technician check it

Circuit/System Description
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). The stop lamps will not operate unless the ignition is in the ON position.

DTC P0572 : Brake Switch Circuit 1 Low Voltage
DTC P0573 : Brake Switch Circuit 1 High Voltage

It's hard to fix something when you don't have a clue how it works . The CC is also a controlled function of the BCM .
The BCM monitors the signal circuit of the cruise control switches. The BCM relays the cruise control switch status to the ECM via the GMLAN serial data circuit. The ECM uses the status of the cruise control switch to determine when to capture and maintain the vehicle speed. The ECM monitors the vehicle speed signal circuit in order to determine and the desired vehicle speed. The ECM uses the TAC motor in order to maintain the vehicle speed. For further review of the TAC system, refer to Throttle Actuator Control (TAC) System Description for the 2.0L engine or to Throttle Actuator Control (TAC) System Description for the 2.4L engine. Ignition voltage is supplied to the cruise control switch from the 2-amp CRUISE fuse located in the integrated BCM fuse block. The cruise control switches are located on the steering wheel. The cruise control function switches are arranged in a resistive ladder design, with each cruise control function switch having a different resistance value. The BCM detects a specific voltage value that is associated with any cruise control function switch being activated. When the normally open cruise control on/off switch is turned ON, the switch closes and the BCM detects a predetermined voltage signal on the cruise control set/coast and resume/accel switch signal circuit. The BCM sends a GMLAN serial data message to the ECM indicating that the On/Off switch is active. Similarly, when the + RES switch or the - SET switch are pressed, the BCM detects the predetermined voltage signal on the cruise control set/coast and resume/accel switch signal circuit. To engage the cruise control system, ensure that the vehicle speed is above 40.2 km/h (25 mph), turn the cruise On/Off switch ON and momentarily press the - SET switch. The ECM will engage the cruise control system and record the vehicle speed. The ECM sends a GMLAN serial data message via the BCM to the driver information center (DIC) in order to display the CRUISE ENGAGED message. The - SET switch or the + RES switch will remain inactive when the BCM has not received the predetermined voltage signal from the On/Off switch. Pressing the accelerator pedal, while the cruise control system is engaged, will allow the driver to override the cruise control system in order to accelerate the vehicle beyond the current set vehicle speed. When the accelerator pedal is released, the vehicle will decelerate and resume the current set vehicle speed. The driver can also override the current set vehicle speed via the - SET switch and the + RES switch. When the cruise control system is engaged, pressing and holding the - SET switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When the - SET switch is released, the ECM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily pressing the - SET switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the - SET is momentarily pressed, with a minimum vehicle speed of 37 km/h (23 mph). Pressing and holding the + RES switch, when the cruise control system is engaged, will allow the vehicle to accelerate to a greater vehicle speed than the current set vehicle speed. When the + RES switch is released, the ECM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily pressing the + RES switch will allow the vehicle to accelerate at 1.6 km/h (1 mph) increments for each time that the + RES switch is momentarily pressed, with the maximum acceleration total of 16 km/h (10 mph) over the current set vehicle speed. Momentarily pressing the + RES switch after the cruise control system has been disengaged by pressing the brake pedal, will recall the previous set vehicle speed that is recorded in the ECM.

It's probably a problem with cruise control module , located under the hood in engine compartment . Or a bad connection somewhere . Do you know how to do electrical testing ? Is the air bag light lit on the instrument cluster ?

Could have DTC'S - diagnostic trouble code's stored .
DTC P1554
The powertrain control module (PCM) inhibits cruise control operation when certain conditions are not appropriate for cruise control operation. The PCM removes the ground from the cruise control inhibit signal circuit in order to disengage cruise control operation.
DTC P1585
Output driver modules (ODMs) are used by the powertrain control module (PCM) in order to turn on many of the current driven devices that are needed to control various engine and transaxle functions. DTC P1558 set indicates that an improper voltage level has been detected on the signal circuit which controls the cruise control inhibit circuit.
Action Taken When the DTC Sets
• The PCM will not illuminate the malfunction indicator lamp (MIL).
• The PCM will store the conditions present when the DTC set as Failure Records data only.

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions. However, steep grades may cause variations in the selected speeds. The electronic cruise control system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE, and TAP-UP or TAP-DOWN.
The main parts of the cruise control system are:
• The cruise control module assembly
• The function control switches
• The cruise control release switch
• The clutch pedal position switch (CPP), if equipped
• The stop lamp switch assembly
• The vehicle speed sensor
The cruise control system uses the cruise control module assembly to maintain the desired vehicle cruise speed and operation. The cruise control module assembly has an electronic controller and an electric stepper motor to vary the throttle in each different cruise control mode. The electric controller monitors vehicle speed and operates the electric stepper motor. The stepper motor operates in response to the electronic controller, to maintain the desired cruise speed. The electric stepper motor moves a strap that is attached to the cruise control cable which moves the throttle linkage. The cruise control module assembly contains a low speed limit which will prevent system engagement below a minimum speed of 40 km/h (25 mph). The module assembly is not serviceable.

Cruise control only maintains speed by utilizing the accelerator. To speed up it increases it and during slowing is removes it. The cruise control will not apply brakes in the event of a steep downhill run. In this case the vehicle will start to accelerate in the same manner as if the cruise control was not engaged. But in theses cases, most cruise controls, once the speed exceeds a certain amount above the set speed, will auto-disengage as a safety feature.

Usually a front speed sensor/wheel hub going bad. is there a humming noise from the front end area while driving at highway speeds? If there is, try to isolate which side it is, and have that hub bearing replaced and make darn sure the axle nut is torqued to the proper spec, or it will fail. To many auto techs just tighten them up withan impact gun, and say its good.

I suggest check the easy things first. Vacuum lines, could cause a lean condition, fuel filter restricting the fuel flow lean condition. Carefully clean throttle body with proper cleaner. I'm a shade tree mechanic but these simple things work sometimes. You didn't mention if you have the cvt trans. If you do and you are going 75 80 on the highway coming to a hill will cause it to race that high. Then when the hill is crested it will slow down, I don't like it either but it is the nature of the beast. I often cancel the cruise on big hills on the highway so it doesn't do that.

Hi,
Yes, this is normal while in four wheel drive on pavement.
I will try and explain why.
In four wheel drive the front and rear drive axles are linked together by a chain in the transfer case and gears in both axles. This is a direct link with very little play between the front and rear axles.
When cornering a rear wheel will spin faster, or slower depending on the direction of the turn. this causes a binding in the drive line because the drive line wants all the wheels to turn at the same speed. So the wheel "skipping" going in reverse, is the drive lines way of compensating for the different speed of the wheels turning.
Never should a four wheel drive be used on dry pavement. I could cause a break in one of the drive line components. On a slippery surface , snow, mud, gravel, grass, There is enough slippage in the surface to aloow the driveline to compensate for the different speeds of tire rotation.
So do not try at highway speeds on dry pavement.
Your four wheel drive system is working just fine.
Wayne

It Sounds Like Your ABS Channels, Its A Separate Hydraulic Circuit That Feeds Out To One Or More Wheel Cylinders Or Caliper Pistons.Anti-Lock Brake Systems Can Have From One To Four Channels.

Start with the simple and check the fuses and the Stop lamp switch. Check your brake lights, if they're not working, the cruise won't work either. If they're not working, check the fuse for them, if the fuse is fine, then take it into the dealer, there's been a recall issued on the brake switch, so it should get fixed for free.
Cruise Control Disengaged
The powertrain control module (PCM) disengages the cruise control operation based on the signals from the following switches:

* The stop lamp switch
* The TCC brake/cruise release switch
* The clutch release switch, if equipped
* The cruise control On/Off switch

The TCC brake/cruise release switch and the stop lamp switch are mounted on the brake pedal bracket. When the brake pedal is applied, the normally closed TCC brake/cruise release switch opens and the normally open stop lamp switch closes. The PCM detects a low signal voltage on the TCC brake/cruise release switch signal circuit and a high signal voltage on the stop lamp switch signal circuit. When the clutch pedal is applied, the normally closed clutch release switch opens and the PCM detects zero voltage on the CCP switch signal circuit. The vehicle speed stored in the memory of the PCM will be erased when the cruise control On/Off button is turned OFF, or the ignition switch is turned OFF.

The Cruise Control System will disengage when the PCM detects that a driver override function has been active for approximately 60 seconds .

When the Cruise Control System is disengaged, the PCM sends a class 2 message to the instrument panel cluster (IPC) in order to deactivate the cruise control indicator.

Cruise Control Inhibited
The powertrain control module (PCM) inhibits the cruise control operation when any of the following conditions exist:

* A cruise control related DTC has been set.
* The vehicle speed is less than 40.2 km/h (25 mph) .
* The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear.
* The engine RPM is too low.
* The engine RPM is too high, with fuel cut off.
* The vehicle speed is too high, with fuel cut off.
* The system voltage is not between 9 volts and 16 volts .
* The Traction Control System (TCS) is active for more than 2 seconds .
Thank you for using Fixya and start with replacing the stop lamp switch. Even though the brake light work, it;s been known for that switch to cause your issue. that's way there was a recall for it.

Hello,
First the vehicle has to be operating at least 35mph. There will be two sets of switches, one set is to the left and the other set is to the right of the horn on the steering wheel. The switches on the left will be labeled on/off, the ones on the right we be labeled Coast/Accel/Resume..

At a steady highway speed press the ON switch, (at the left hand side of the horn) This will activate and turn the speed control system ON...

Then you have to set and adjust your desired speed...

To SET YOUR DESIRED speed , press and hold the accel switch (Right side of Horn) until your desired speed has been reached and then release the switch.. Speed control will now be on, activated and set, you will be in cruise mode..

If you need to coast due to possible traffic, press and hold the coast switch as long as you need to.. This is like taking your foot off of the accelerator pedal.. When you let go of the coast switch you will return to you set cruising speed.

Stepping on the brake pedal at any time will deactivate the system.. If you step on the brake, and then want to return to your previous set cruising speed... All you have to do is press resume...

I hope this has helped you? You can find detailed speed control activation instructions in your 2005 Ford Focus Owners manual.. If you did not receive your owners manual when you bought the vehicle.. You can purchase one at your local Ford, Lincoln or Mercury dealership..

Bill Andrade Ford Master Technician/Shop Foreman

If set at a specific speed and you have to slow down by hitting the brakes, The brakes turn off the cruise control. Pressing resume automatically turns the cruise control back on and accelerates to the previous speed setting. You can also use it to accelerate and by releasing it the new speed will be set.