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Home >> GMC >> 1983 >> Jimmy 6.2 C >> Repair and Diagnosis >> Accessories & Equipment >> Cruise Control Systems >> Description & Operation >> Servo Check

Servo Check

  1. Disconnect the electrical connector at the servo. Make sure the connector and pins are free of corrosion. Check resistances. Resistances should be as follows. If not, replace servo unit.
    SERVO PIN RESISTANCES

    Pin Number Ohms
    A-C 10
    E-C 10
    B-D 5
  2. Turn off ignition switch then disconnect the body harness connector from the Vehicle Speed Sensor buffer amplifier. Connect a Speedometer Signal Generator (J-33431) to amplifier connector. Disconnect the servo throttle linkage at the servo unit. Set the signal generator to 54 MPH and 30 Hertz square wave position. Start the engine and move mode switch slider to "ON" position.
  3. Depress and release "SET/COAST" switch. Servo should pull to approximately 28-42% of servo position travel and hold. Move cruise lever and slider to "RESUME ACCEL" position and hold for 3 seconds. Servo will pull to the full stroke position and hold.
  4. After releasing slider from the "RESUME ACCEL" position, the servo will return to 28-42% of the travel position. Momentarily move the CRUISE lever slider to "RESUME ACCEL" position. Servo will pull to the 28-42% position of travel and hold.
  5. If tests in steps 3) and 4) do not perform as indicated, check the harness for defects, then make electrical and pneumatic tests as needed. If steps 3) and 4) do perform as indicated, a buffer amplifier or pulse modulator generator defect is indicated.
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