I had the problem with my 99 Explorer. As it happens, the problem was the deactivator switch on the brake master cylinder. It's the unit at the very front of the master cylinder with the electrical connector and a common failure. I've copied a test procedure from the Ford Workshop Manual for a 96. Hope it helps.
Section 10-03A: Speed Control System, Electronic, Ranger, Explorer 1996 Ranger and Explorer Workshop Manual
DIAGNOSIS AND TESTING
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Pinpoint Tests
PINPOINT TEST A: SPEED CONTROL INOPERATIVE
A1 VERIFY THERE IS POWER TO SPEED CONTROL SERVO
Disconnect harness connector from the speed control servo.
Use Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to make the specified measurements at the harness connector. To avoid terminal damage, use Rotunda Terminal Adapter Kit 105-00025 or equivalent.
With the ignition switch in RUN, measure voltage between Pin 7 (Circuit 1003) and Pin 10 (Circuit 676).
Is there battery voltage (12v nom.)?
Yes No
GO to A2 . GO to B1 .
A2 CHECK FOR STUCK STOPLIGHT SWITCH
With no brakes applied, measure the voltage between Pin 4 (Circuit 306) and Pin 10 (Circuit 676).
Is the battery voltage (12v nom.)?
Yes No
Stoplight switch is stuck on. REPLACE stoplight switch. Stoplight switch is OK. GO to A3 .
A3 CHECK BRAKE/CLUTCH CIRCUIT
With the ignition switch in OFF position, measure the resistance between Pin 4 (Circuit 306) and Pin 10 (Circuit 676).
Is resistance less than 20 ohms?
Yes No
Brake input Circuit OK. GO to A4 . Brake light bulbs blown or brake circuit open. SERVICE circuit including clutch pedal position switch.
A4 CHECK DEACTIVATOR SWITCH CIRCUIT
Turn the ignition switch to RUN position.
With no brakes applied, place a 12-volt circuit test light between Pin 9, Circuit 307 (BK/Y) and Pin 10, (GND, Circuit 676 PK/O).
Is the light illuminated?
Yes No
GO to A7 . GO to A5 .
A5 VERIFY POWER AT DEACTIVATOR SWITCH HARNESS CONNECTOR
Remove wiring harness connector from deactivator switch.
Place 12-volt circuit test light between Circuit 1003 (GY/Y) of deactivator switch connector and chassis ground.
Is the light illuminated?
Yes No
GO to A6 . SERVICE blown fuse 11 or open Circuit 1003 (GY/Y).
A6 CHECK FOR OPEN CIRCUIT BETWEEN DEACTIVATOR SWITCH AND SPEED CONTROL SERVO
Measure resistance of Circuit 307 (BK/Y) from deactivator switch connector to Pin 9 of speed control servo connector.
Is resistance less than 1 ohm?
Yes No
REPLACE deactivator switch. SERVICE open Circuit 307 (BK/Y) in harness.
A7 CHECK FOR STUCK "ON" SPEED CONTROL ACTUATOR SWITCH ASSEMBLY
With no steering wheel switches pressed, measure voltage between Pin 5 (Circuit 151 [LB/BK]) and Pin 10 (GND, Circuit 676 [ PK/O]).
Is there battery voltage?
Yes No
REPLACE left (ON/OFF) speed control actuator switch. GO to A8 .
A8 CHECK ON SWITCH OPERATION
With steering wheel ON switch pressed, measure voltage between Pin 5 (COMMAND, Circuit 151) and Pin 10 (GND, Circuit 676).
Is there battery voltage (12v nom.)?
Yes No
GO to A12 . GO to A9 .
A9 VERIFY POWER AT AIR BAG SLIDING CONTACT CONNECTOR AT BASE OF STEERING COLUMN
Disconnect air bag sliding contact at 6-pin connector at the base of steering column.
Measure voltage between Circuit 6 (Y/LG) at air bag sliding contact connector on instrument panel harness and Pin 10 (Circuit 676) of speed control servo connector.
Is there battery voltage?
Yes No
GO to A10 . CHECK fuse in the engine compartment fuse panel. Circuit 460 (Y/LB) horn relay and Circuit 6 (Y/LG). SERVICE as necessary.
A10 CHECK AIR BAG SLIDING CONTACT FOR HIGH RESISTANCE
Disconnect speed control actuator switch 5-pin connector from air bag sliding contact.
Measure resistance across each of the air bag sliding contact windings between the air bag sliding contact connector at the base of steering column and speed control switches connector in steering wheel.
Is each resistance reading less than 1.0 ohm?
Yes No
GO to A11 . REPLACE air bag sliding contact.
A11 CHECK FOR OPEN CIRCUIT IN STEERING WHEEL WIRING HARNESS
Reconnect air bag sliding contact assembly at base of steering column.
Disconnect connector at ON/OFF switch.
Measure voltage between Pin 5 (Circuit 151) and chassis ground ( steering wheel).
Is there battery voltage?
Yes No
REPLACE left (ON/OFF) speed control actuator switch. REPLACE steering wheel wiring harness.
A12 CHECK FOR STUCK COMMAND SWITCHES
With no steering wheel switches pressed, measure resistance between Pin 5 (Circuit 151) and Pin 6 (COMMAND RTN, Circuit 848).
Is resistance greater than 3k Ohms?
Yes No
GO to A13 . If resistance is less than 100 ohms, REPLACE left (ON/OFF) switch. If greater than 100 ohms, REPLACE right (RSM/SET/COAST) switch.
A13 CHECK SET/ACCEL SWITCH OPERATION
With the SET/ACCEL switch pressed, measure the resistance between Pin 5 (COMMAND, Circuit 151) and Pin 6 (COMMAND RTN, Circuit 848).
Is resistance between 646 and 714 ohms?
Yes No
GO to A14 . REPLACE right (RSM/SET/COAST) speed control actuator switch.
A14 CHECK COAST SWITCH OPERATION
With COAST switch pressed, measure resistance between Pin 5 (Circuit 151 [ LB/BK]) and Pin 6 (Circuit 848 [DG/O]).
Is resistance between 114 and 126 ohms?
Yes No
GO to A15 . REPLACE right (RSM/SET/COAST) speed control actuator switch.
A15 CHECK RESUME SWITCH OPERATION
Disconnect harness connector from speed control servo assembly.
With RSM switch pressed, measure resistance between Pin 5 (Circuit 151 [ LB/BK]) and Pin 6 (Circuit 848 [DG/O]).
Is resistance between 2090 and 2310 ohms?
Yes No
GO to A16 . REPLACE right (RSM/SET/COAST) speed control actuator switch.
A16 CHECK OFF SWITCH OPERATION
Disconnect harness connector from speed control servo. With OFF switch pressed, measure resistance between Pin 5 (Circuit 151 [ LB/BK]) and Pin 6 (Circuit 848 [DG/O]).
Is resistance less than 4 ohms?
Yes No
GO to A17 . REPLACE left (ON/OFF) speed control actuator switch.
A17 CHECK COMMAND SWITCH RETURN CIRCUIT
Measure resistance between Pin 6 (Circuit 848 [ DG/O]) and Pin 10 (GND, Circuit 676 [PK/O]).
Is resistance greater than 1 ohm?
Yes No
GO to A18 . SERVICE short in Circuit 848 (DG/O). RECONNECT speed control servo.
A18 CHECK VSS CIRCUIT
Measure resistance between Pin 3 (Circuit 679 [ GY/BK]) and Pin 10 (Circuit 676 [PK/O]).
Is resistance between 200 and 300 ohms?
Yes No
GO to A20 . GO to A19 .
A19 CHECK VSS
Remove VSS connector.
Measure resistance across VSS terminals.
Is resistance between 200 and 300 ohms?
Yes No
CHECK for opens or shorts in Circuit 679 (GY/BK) and 676 (PK/O). REPLACE vehicle speed sensor.
A20 ROAD TEST VEHICLE
Road test vehicle and observe speedometer needle.
Does the needle waver?
Yes No
REPLACE vehicle speed sensor. Vehicle speed sensor checks OK. GO to A21 .
A21 CHECK FOR BROKEN OR BINDING CABLE
Remove speed control actuator cable from speed control servo assembly.
Check for broken or binding cable by pulling on cable ball slug to ensure throttle moves freely.
Is cable OK?
Yes No
REPLACE speed control servo assembly. REPLACE speed control actuator cable.
PINPOINT TEST B: NO POWER TO SERVO
B1 CHECK IGNITION CIRCUIT
Make sure Step A1 has been done.
With ignition switch in the RUN position, measure the voltage between Pin 7 (Circuit 1003) and ground point on the chassis.
Is there battery voltage (12v nom.)?
Yes No
Ignition circuit OK. GO to B2 . Ignition input is open circuit. REPLACE fuse or SERVICE as required.
B2 CHECK MODULE GROUND CIRCUIT
With ignition switch in OFF position, measure the resistance between Pin 10 (GND, Circuit 676) and ground point on the chassis.
Is resistance less than 1 ohm?
Yes No
Module power OK. REPEAT Step A1 . GND circuit open. SERVICE as required.
PINPOINT TEST C: SET SPEED FLUCTUATES
C1 CHECK THE CONDITION OCCURS ONLY WHILE USING SPEED CONTROL
Verify that engine is properly tuned.
Verify that condition does not occur when driving without speed control.
Does condition occur without speed control?
Yes No
SERVICE engine as required. GO to C2 .
C2 CHECK FOR BINDING IN SPEED CONTROL ACTUATOR CABLE AND THROTTLE BODY LINKAGE
Check for binding or sticking of speed control cable or throttle linkage and throttle plate.
Make sure throttle cable bracket and speed control servo bracket are not loose.
Are components OK?
Yes No
GO to C3 . SERVICE as required.
C3 CHECK VSS CIRCUIT
Measure resistance between Pin 3 (Circuit 679 [ GY/BK]) and Pin 10 (Circuit 676 [PK/O]).
Is resistance between 200 and 300 ohms?
Yes No
GO to C5 . GO to C4 .
C4 CHECK VSS
Remove VSS connector.
Measure resistance across VSS terminals.
Is resistance between 200 and 300 ohms?
Yes No
CHECK for opens or shorts Circuit 679 (GY/BK) and 676 (PK/O). REPLACE vehicle speed sensor.
C5 ROAD TEST VEHICLE
Road test vehicle and observe speedometer needle.
Does the needle waver?
Yes No
REPLACE vehicle speed sensor. Vehicle speed sensor checks OK. GO to C6 .
C6 CHECK SPEED CONTROL SERVO ASSEMBLY
Substitute know good speed control servo.
Test vehicle for proper operation.
Does system operate properly?
Yes No
REPLACE speed control servo assembly. CHECK MAP sensor and EGR valve position (EVP) sensor and speed control cable adjustment.
PINPOINT TEST D: SPEED CONTROL DOES NOT DISENGAGE WHEN BRAKES ARE APPLIED
D1 CHECK DEACTIVATOR SWITCH CIRCUIT
Turn ignition switch to RUN.
Disconnect harness connector from the speed control servo.
With no brakes applied, place a 12 Volt Circuit Test Light between Pin 9 (Circuit 307 [BK/Y]) and Pin 10 (GND, Circuit 676 [ PK/O]).
Is the light illuminated?
Yes No
GO to D2 . REFER to Pinpoint Test A — Speed Control Inoperative.
D2 CHECK DEACTIVATOR SWITCH OPERATION
Leave ignition switch in RUN.
Fully apply brakes with the 12-Volt Circuit Test Light still between Pin 9 (Circuit 307 [BK/Y]) and Pin 10 (GND, Circuit 676 [ PK/O]).
Does the light turn off?
Yes No
GO to D3 . REPLACE deactivator switch.
D3 CHECK STOPLIGHT SWITCH CIRCUIT
With brakes applied, measure voltage between Pin 4 (Circuit 306 [ T/LB]) and Pin 10 (GND Circuit 676 [ PK/O]).
Is there battery voltage?
Yes No
GO to D4 . SERVICE stoplight switch, Fuse 11, or open in Circuit 306 (T/LB). RECONNECT speed control servo.
D4 CHECK FOR BINDS IN SPEED CONTROL ACTUATOR CABLE AND THROTTLE BODY ATTACHMENT
Remove speed control actuator cable from speed control servo.
Check for broken or binding cable by pulling on cable ball slug to ensure throttle moves freely.
Is cable OK?
Yes No
REPLACE speed control servo. SERVICE as required. RECONNECT speed control servo.
PINPOINT TEST E: SPEED CONTROL INDICATOR DOES NOT TURN ON
E1 CHECK VOLTAGE AT SPEED CONTROL SERVO ASSEMBLY CONNECTOR
Disconnect harness connector from speed control servo.
With ignition switch in RUN, measure voltage between Pin 1 (Circuit 203 [ O/LB]) and Pin 10 (GND Circuit 676 [ PK/O]).
Is voltage approximately battery voltage?
Yes No
GO to E3 . GO to E2 .
E2 CHECK CIRCUIT CONTINUITY
Measure resistance of Circuit 203 (O/LB) from Pin 1 of speed control servo connector to instrument cluster connector.
Is resistance less than one ohm?
Yes No
Go to E3 . SERVICE open in Circuit 203 (O/LB).
E3 DISPLAY TURN ON TEST
With ignition switch in RUN, connect Pin 1 (Circuit 203 [ O/LB]) to Pin 10 (GND, Circuit 676 [ PK/O]).
Does Speed Control display turn on?
Yes No
REPLACE speed control servo and REPEAT test. SERVICE instrument cluster. REFER to Section 13-00 or Section 13-01 .
PINPOINT TEST F: SPEED CONTROL INDICATOR DOES NOT TURN OFF
F1 CHECK CIRCUIT 203
Check for short to ground in Circuit 203 (O/LB).
Is there a short?
Yes No
SERVICE Circuit 203 (O/LB). SERVICE instrument cluster. REFER to Section 13-00 or Section 13-01 .
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As for the key in ignition buzzer there is a switch in the steering column attached to the ignition switch that senses the key is in the lock. Mine is also troublesome. Sometimes it works, sometimes not. The cure is to replace the switch.
