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Servo Test

  1. Turn ignition off. Disconnect connector from control module assembly. Using an ohmmeter, probe between connector and cavity pins "F" (circuit 398) and "H" (circuit 399). Resistance should be between 20-30 ohms.
  2. If reading is 20-30 ohms, continue test on step 5). If reading is not within specifications, disconnect servo electrical connector from servo. With ohmmeter probes between pins "B" (circuit 399) and "D" (circuit 398) on servo assembly. Resistance should be between 20-30 ohms.
  3. If reading is not within specifications, replace servo. If reading is 20-30 ohms, check circuit 399 between pin "H" of control module and pin "B" of servo for loose connections or open wires. Repair or replace as necessary.
  4. Check circuit 398 between pin "F" of control module and pin "D" of servo for loose connections or open wires. Repair or replace as necessary, continue test.
  5. Using ohmmeter, probe between control module connector cavity pin "C" (circuit 430) and ground. Resistance should be infinity (open circuit). If continuity is indicated, locate short to ground and repair circuit 430 as necessary.
  6. If no continuity is indicated, leave ohmmeter connected as is. Using a jumper wire, connect cavity "A" of servo connector to ground. Resistance should be 0 ohms.
  7. If reading is not within specifications, locate open in circuit 430 between pin "C" of control module to pin "A" of servo. Repair or replace as necessary. If reading is within specifications, remove jumper wire and continue test.
  8. Using an ohmmeter, probe between control module cavity pin "K" (circuit 402) and ground. Resistance should be infinity. If continuity is indicated, locate short to ground and repair circuit 402.
  9. If no continuity is indicated, leave ohmmeter connected as is. Using a jumper wire, connect cavity "E" of servo connector to ground. Resistance should be 0 ohms.
  10. If reading is not within specifications, locate open in circuit 402 between pin "K" of control module to pin "E" of servo. Repair or replace as necessary. If reading is within specifications, continue test.
  11. Using an ohmmeter, probe connector cavity pin "C" (circuit 150) and ground. Resistance should be 0 ohms. If reading is 0 ohms, continue test on step 14).
  12. If reading is not within specifications, disconnect electrical connector from control module. Using an ohmmeter, probe connector cavity "J" (circuit 150) and ground. Resistance should be 0 ohms.
  13. If reading is not within specifications, locate open in circuit 150 between pin "J" of control module to ground (point G202). Repair or replace as necessary. If reading is 0 ohms, locate open in circuit 150 between pin "C" of servo to (S253) splice. Repair or replace as necessary.
  14. Disconnect linkage, bead chain or cable from servo to throttle. Ensure electrical connector to servo is still disconnected. Start engine and let idle. Manually actuate servo vent and vacuum control valves by connecting jumper wires from battery positive post to pins "A" and "E" on servo assembly
  15. Connect another jumper wire between pin "C" of servo and ground. With brake and clutch pedal (M/T) in free position, servo should fully pull in. If servo fails to pull in, go to step 18).
  16. If servo pulls in, remove jumper wire from pin "E" on servo. Servo should stay in position. If servo stays in position, check connection of electrical connector at servo. If servo fails to remain in position, remove larger of two hoses and plug orifice of servo.
  17. Reconnect jumper wire to pin "E" until servo fully pulls in, then remove jumper wire. If servo fails to stay in position, replace servo. If servo stays in position, check brake and/or clutch release valve for adjustment. Check hoses and valves for leaks, repair or replace as necessary. Check for proper system operation.
  18. Remove larger of two hoses and plug orifice of servo. Servo should pull in. If servo fails to pull in, remove smaller hose from servo and check for vacuum. If vacuum is present, inspect connectors for leaks. If okay, replace servo.
  19. If no vacuum is present, check connectors between servo and vacuum source. Repair or replace as necessary. If servo pulls in, check brake and/or clutch release valve for adjustment. Check hoses and valves for leaks, repair or replace as necessary.
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