Pinpoint Test B: The Set Speed Fluctuates
- B1 CHECK THE SPEED CONTROL CABLE/THROTTLE BODY LINKAGE
- Key in OFF position.
- Visually inspect the speed control cable connections, the throttle body linkage, and the speed control actuator pulley cover.
- Are the speed control cable connections, the throttle body linkage, and the speed control actuator pulley cover OK?
Yes : GO to B2.
No : INSTALL a new speed control cable or REPAIR the throttle body linkage. To INSTALL a new speed control cable, REFER to SPEED CONTROL CABLE in this article. TEST the system for normal operation. For repair of the throttle body linkage, REFER to FUEL SYSTEM-GENERAL INFORMATION . TEST the system for normal operation. For repair of the speed control actuator pulley cover, INSTALL the cover correctly. TEST the system for normal operation.
- B2 CHECK THE SPEEDOMETER OPERATION
- Drive the vehicle and observe the speedometer operation.
- Does the speedometer needle fluctuate?
Yes : REFER to INSTRUMENT CLUSTER to continue diagnosis of the speedometer.
No : GO to B3.
- B3 CHECK FOR A BASE ENGINE CONCERN
- Drive the vehicle and determine if there is a base engine concern.
- Is a base engine concern present?
Yes : REFER to the INTRODUCTION - GASOLINE or INTRODUCTION -- HYBRID ESCAPE & HYBRID MARINER article to continue diagnosis of the base engine concern.
No : GO to B4.
- B4 CHECK THE VEHICLE SPEED SIGNAL VOLTAGE CAUTION: Make sure the vehicle is secured correctly before attempting to place the transmission range selector lever in DRIVE or in first gear if equipped with a manual transmission.
- Disconnect: Speed Control Actuator C122.
- Connect: ABS Module C155.
- Disconnect: Active Torque Coupling C3254.
- Jack up the drive wheels and chock the other wheels.
- Start the vehicle, place the transmission in DRIVE and with the engine at idle allow the drive wheels to spin.
- Measure and record the AC voltage between the speed control actuator C122-3, circuit 679 (GY/BK), harness side and ground with the vehicle drive wheels spinning a minimum of 8 km/h (5 mph) and the speedometer registers a speed.
- Apply the brakes until the drive wheels come to a stop. Place the transaxle in PARK, fully engage the parking brake and turn the engine off.
- Is the AC voltage greater than 4.5 volts?
NOTE: For vehicles with a manual transaxle, place the transaxle into first gear.Yes : GO to B5.
No : GO to B6.
- B5 CHECK THE VEHICLE SPEED SIGNAL FREQUENCY CAUTION: Make sure the vehicle is secured correctly before attempting to place the transmission range selector lever in DRIVE or in first gear if equipped with a manual transmission.
- Start the vehicle, place the transmission in DRIVE and with the engine at idle allow the drive wheels to spin.
- Measure and record the frequency between the speed control actuator C122-3, circuit 679 (GY/BK), harness side and ground with the vehicle drive wheels spinning a minimum of 8 km/h (5 mph) and the speedometer registers a speed. Record the speedometer reading.
- Apply the brakes until the drive wheels come to a stop. Place the transaxle in PARK, fully engage the parking brake and turn the engine off.
- Divide the frequency reading by 2.2 to get a mph result and compare this to the reading of the speedometer.
- Does the frequency reading result match the speedometer reading?
NOTE: For vehicles with a manual transaxle, place the transaxle into first gear.Yes : INSTALL a new speed control actuator. REFER to SPEED CONTROL ACTUATOR in this article. TEST the system for normal operation.
No : GO to B6.
- B6 CHECK FOR CORRECT ABS MODULE OPERATION
- Disconnect the ABS module connector.
- Check for:
- corrosion
- pushed-out pins
- Connect the ABS module connector and make sure it seats correctly.
- Operate the system and verify the concern is still present.
- Is the concern still presents?
Yes : INSTALL a new ABS module. REFER to VEHICLE DYNAMIC SYSTEMS . TEST the system for normal operation.
No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.