Sport trac cruise control works off and on

First thing , knowing what all is involved in the cruise control system helps
Speed Control The speed control system is designed to maintain vehicle speed between 48 and 200 km/h (30 and 125 mph).
Normally, when the brake pedal is applied, the speed control module deactivates the speed control system. Under increased brake pedal effort, the deactivator switch, a normally closed switch, will open and remove power to the speed control actuator clutch, releasing the throttle independently of the speed control module.

Principles of Operation
The brake pedal position (BPP) switch is normally closed to ground. When the brake pedal is applied with the speed control system engaged, the BPP switch closes (to battery voltage), putting the speed control in stand-by mode.
NOTE: A redundant brake deactivator (BPA) switch is provided as an additional safety feature.
NOTE: The speed control module is integral to the powertrain control module (PCM).
The clockspring provides the electrical interface between the steering column wiring and the speed control switches in the steering wheel.
The inputs to the powertrain control module (PCM) required to operate the speed control system are the:

• anti-lock brake (ABS) module
• digital transmission range (TR) sensor
• speed control deactivator switch
• speed control switches
• vehicle speed signal (VSS)

The inputs to the speed control actuator come from the powertrain control module (PCM).
The outputs of the speed control actuator go to the speed control cable controlled throttle position sensor.

Special Tool(s) 73III Automotive Meter
105-R0057 or equivalent Worldwide Diagnostic System (WDS)
418-F224,

New Generation STAR (NGS) Tester
418-F052, or equivalent diagnostic tool with appropriate adapter cable
Inspection and Verification

1. Verify the customer concern.

1. Verify the speedometer operates correctly without using the speed control by test driving the vehicle. If the speedometer does not operate correctly, refer to Section 413-00 .

1. Verify the stoplamps operate correctly with the ignition switch in the OFF position. If the stoplamps do not operate correctly, refer to Section 417-01 .

1. Verify the parking brake is not applied and is operating correctly. If the parking brake is not operating correctly, refer to Section 206-00 .

1. Visually inspect for obvious signs of mechanical and electrical damage.

Visual Inspection Chart Mechanical Electrical

• Speed control cable
• Throttle lever
• Speed control actuator

• Battery junction box (BJB) fuse 40 (15A)
• Circuitry
• Powertrain control module (PCM)

1. If the concern remains after the inspection, connect the diagnostic tool to the data link connector (DLC) and select the vehicle to be tested from the diagnostic tool menu. If the diagnostic tool does not communicate with the vehicle:
   • check that the program card is correctly installed.
   • check the connections to the vehicle.
   • check the ignition switch position.

1. If the diagnostic tool still does not communicate with the vehicle, refer to the diagnostic tool operating manual.

1. Carry out the diagnostic tool data link test. If the diagnostic tool responds with:
   • SCP or ISO circuit fault; all electronic control units no response/not equipped, refer to Section 418-00 .
   • No response/not equipped for PCM, Go To Pinpoint Test A .
   • System passed, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and carry out the KOEO Test.

1. If the DTCs retrieved are related to the concern, go to the Powertrain Control Module (PCM) Diagnostic Trouble Code (DTC) Index to continue diagnostics.

1. If no DTCs related to the concern are retrieved, proceed to the Symptom Chart to continue diagnostics.

NOTE: DTC P0703 and DTC P1572 must be repaired before any other DTC.

Powertrain Control Module (PCM) Diagnostic Trouble Code (DTC) Index DTCs Description Source Action P0500 Vehicle Speed Error PCM REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual. P1565 Speed Control Command Switches High/Out of Range PCM Go To Pinpoint Test A . P1566 Speed Control Command Switches Low/Out of Range PCM Go To Pinpoint Test B . P1567 Speed Control Output Circuit PCM Go To Pinpoint Test C . P1568 Speed Control Unable to Hold Speed PCM Go To Pinpoint Test D . P1572 Brake On/Off Failure PCM Go To Pinpoint Test E . P0703 Brake Switch Input Malfunction PCM Go To Pinpoint Test E . IF thier are no codes go to the Symptom Chart

Symptom Chart Condition Possible Sources Action

• No communication with the powertrain control module (PCM)

• Battery junction box (BJB) fuse(s):
  • 11 (40A)
  • 40 (15A).
• Circuitry.
• PCM.

• REFER to Section 418-00 to continue communication diagnostics.

• The speed control switch is inoperative - no DTCs

• Speed control switch.

• INSTALL a new speed control switch. REFER to Speed Control Switch - With Remote Audio/Climate Controls or Speed Control Switch - Without Remote Audio/Climate Controls in this section.

• The speed control is inoperative - no DTCs

• Low battery voltage.
• Circuitry.
• Digital transmission range (TR) sensor (automatic transmission only).
• Parking brake switch.

• Go To Pinpoint Test F .

• The speed control indicator lamp is always on

• Circuitry.
• Instrument cluster.
• Powertrain control module (PCM).

• Go To Pinpoint Test G .