Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD1999MUSTANG GT, 2D CONVERTIBLE, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)EXTERNAL PAGESDIFFERENT CARSECTION 53 (ENGINE CONTROLS - TROUBLE SHOOTING - NO CODES - EEC-V - DIESEL)SYMPTOMSCRUISE (SPEED) CONTROL CONCERNS
1999 Ford Mustang GT, 2D Convertible, Standard
Cruise (Speed) Control Concerns
1999 Ford Mustang GT, 2D Convertible, StandardSECTION Cruise (Speed) Control Concerns
WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 2002 Ford RV Cutaway, 2002 Ford Pickup, 2002 Ford F550 Super Duty, 2002 Ford F450 Super Duty, and 2002 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.
- Check ABS Light
Turn ignition on and observe ABS light. ABS light should illuminate for a couple of seconds, then turn off (bulb check). If ABS light operates as specified, turn ignition off and go to next step. If ABS stays on, service ABS system as necessary. See appropriate ANTI-LOCK article in BRAKES. - Check Brake Warning Light
Turn ignition on and observe BRAKE warning light. Brake warning light should illuminate for a couple of seconds, then turn off (bulb check). If BRAKE warning light operates as specified, go to next step. If BRAKE warning light remains illuminated, see TEST FF: PARKING BRAKE APPLIED SWITCH in SELF-DIAGNOSTICS - EEC-V - DIESEL article. - Perform KOEO On-Demand Self-Test
Perform KOEO ON-DEMAND SELF-TEST under QUICK TEST in SELF-DIAGNOSTICS - EEC-V - DIESEL article. If no DTCs are present, go to next step. If any DTCs are present, see go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - EEC-V - DIESEL article and perform appropriate SYSTEM TESTS. - Perform KOER Switch Self-Test
Perform KOER SWITCH SELF-TEST under QUICK TEST in SELF-DIAGNOSTICS - EEC-V - DIESEL article. If no DTCs are present, go to next step. If any DTCs are present, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - EEC-V - DIESEL article and perform appropriate SYSTEM TESTS. - Road Test
Using scan tool, access and monitor PBA, BPA, CPP, BOO, SCCS_M, VSS and VS SET PIDs from PID/DATA MONITOR & RECORD menu. See PARAMETER IDENTIFICATION MODE and DRIVER OPERATED CONTROLS CHECK under ADDITIONAL SYSTEM FUNCTIONS in SELF-DIAGNOSTICS - EEC-V - DIESEL article. Drive vehicle and operate speed control system. Compare VSS PID value to speedometer value. If scan tool displays the correct PID value for each PID selected, go to next step. If scan tool displays an incorrect PID value for any PID selected, perform appropriate test listed in PARAMETER IDENTIFICATION VALUES table under DRIVER OPERATED CONTROLS CHECK under ADDITIONAL SYSTEM FUNCTIONS in SELF-DIAGNOSTICS - EEC-V - DIESEL article. - Check Speed Control
If speed control drops out while driving up hills, engine power is not adequate to hold hill, go to next step. If speed control does not drop out when climbing hills, go to RUNS ROUGH, MISSES, BUCKS OR JERKS, HESITATION, STUMBLES, SURGES (ON ACCELERATION OR CRUISE), LACK OR LOSS OF POWER, OR POOR FUEL ECONOMY symptom. - Check Vehicle Load
If vehicle is too heavy to hold hills, vehicle speed dropped 10 MPH below set speed causing speed control disengagement. Confirm condition with scan tool. Access and monitor VSS and VS SET PIDs. If vehicle is able to hold hills, see RUNS ROUGH, MISSES, BUCKS OR JERKS, HESITATION, STUMBLES, SURGES (ON ACCELERATION OR CRUISE), LACK OR LOSS OF POWER, OR POOR FUEL ECONOMY symptom.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.