Dodge Durango Service ManualSpeed Control System » Description and operation
Speed control servo
Speed control servo
DESCRIPTION
The servo unit consists of a solenoid valve body, and a vacuum chamber. The solenoid valve body contains three solenoids:
- Vacuum
- Vent
- Dump
The vacuum chamber contains a diaphragm with a cable attached to control the throttle linkage.
OPERATION
The Powertrain Control Module (PCM) controls the solenoid valve body. The solenoid valve body controls the application and release of vacuum to the diaphragm of the vacuum servo. The servo unit cannot be repaired and is serviced only as a complete assembly.
Power is supplied to the servo's by the PCM through the brake switch. The PCM controls the ground path for the vacuum and vent solenoids.
The dump solenoid is energized anytime it receives power. If power to the dump solenoid is interrupted, the solenoid dumps vacuum in the servo. This provides a safety backup to the vent and vacuum solenoids.
The vacuum and vent solenoids must be grounded at the PCM to operate. When the PCM grounds the vacuum servo solenoid, the solenoid allows vacuum to enter the servo and pull open the throttle plate using the cable. When the PCM breaks the ground, the solenoid closes and no more vacuum is allowed to enter the servo. The PCM also operates the vent solenoid via ground. The vent solenoid opens and closes a passage to bleed or hold vacuum in the servo as required.
The PCM duty cycles the vacuum and vent solenoids to maintain the set speed, or to accelerate and decelerate the vehicle. To increase throttle opening, the PCM grounds the vacuum and vent solenoids. To decrease throttle opening, the PCM removes the grounds from the vacuum and vent solenoids. When the brake is released, if vehicle speed exceeds 30 mph to resume, 35 mph to set, and the RES/ACCEL switch has been depressed, ground for the vent and vacuum circuits is restored.
Speed control system
Speed control servo
Speed control solenoid circuits
Speed control switches
Brake lamp switch
Servo cable
Vacuum reservoir
Vehicle speed input
Dodge Durango Service Manual
- Lubrication and Maintenance
- Suspension
- Differential and Driveline
- Brakes
- Cooling System
- Battery
- Starting Systems
- Charging System
- Ignition System
- Instrument Panel Systems
- Audio Systems
- Horn Systems
- Speed Control System
- Turn Signal and Hazard Warning Systems
- Wiper and Washer Systems
- Lamps
- Passive Restraint Systems
- Electrically Heated Systems
- Power Distribution System
- Power Lock Systems
- Vehicle Theft/Security Systems
- Power Seat System
- Power Window Systems
- Power Mirror Systems
- Chime/Buzzer Warning Systems
- Overhead Console Systems
- Engine
- Exhaust System
- Frame and Bumpers
- Fuel System
- Steering
- Transmission and Transfer Case
- Tires and Wheels
- Body
- Heating and Air Conditioning
- Emission Control Systems
- Introduction
Categories
0.006