LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Cadillac >> 1984 >> Cimarron Standard >> Repair and Diagnosis >> Accessories & Equipment >> Cruise Control Systems >> Testing >> Servo Test
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Servo Test

  1. Turn ignition off. Disconnect connector from control module assembly. With an ohmmeter probe between connector cavity pins F (circuit 398) and H (circuit 399). Check for resistance of 20-30 ohms.
  2. If resistance in step 1) is incorrect, disconnect electrical connector from servo. With an ohmmeter, probe between pins D (circuit 399) and B (circuit 398) on the servo assembly.
  3. If resistance in step 2) is 20-30 ohms, check circuits 399 and 398 (pin H of control module to pin B of servo, and pin F of control module to pin D of servo). There should be zero ohms in each circuit. If not repair wiring. If resistance in step 2) is not 20-30 ohms, replace servo.
  4. If resistance in step 1) is correct, turn off ignition. Disconnect connectors from control module and servo assemblies. With an ohmmeter, probe between connector pin cavity C (circuit 403) and ground. Measure resistance of wire.
  5. If continuity is indicated in step 4), find short to ground and repair (circuit 403). If no continuity is indicated, leave ohmmeter connected. Use jumper wire to connect cavity A of servo to ground. Measure resistance.
  6. If resistance measures zero ohms, go to step 7). If resistance does not measure zero ohms, find open in circuit 403 (pin C of control module to pin A of connector). Repair or replace as necessary.
  7. If resistance in step 5) measured zero ohms, remove jumper wire and with ohmmeter connected between control module connector cavity pin K and ground, check for continuity.
  8. If continuity is indicated in step 7), find short to ground and repair. If no continuity is indicated, leave ohmmeter connected and use a jumper wire to connect cavity E of servo connector to ground. Measure resistance.
  9. If resistance is zero ohms, go to step 10). If resistance is not zero ohms, find open in circuit 402 (pin K of control module to pin E of servo). Repair or replace as necessary.
  10. Turn ignition off. Disconnect connector from servo. Probe connector cavity pin C to ground. Measure resistance. If resistance is zero ohms, go to step 13). If resistance is not zero ohms, disconnect electrical connector from control module.
  11. With ohmmeter probe connector cavity J (circuit 150) to ground. If resistance is not zero ohms, find open in circuit 150 (pin J of control module to ground point G202). Repair or replace as necessary.
  12. If resistance in step 11) was zero ohms, find open in circuit 150 (pin C of servo to splice S243). Repair or replace as necessary.
  13. If resistance in step 10) was zero ohms, disconnect linkage, chain or cable to throttle. Make sure the electrical connector to the servo is still disconnected. Start the engine and let idle.
  14. Manually actuate the servo vent and vacuum control valves by connecting jumper wires from positive battery terminal to pins A and E on servo assembly. With another jumper wire, connect one end to pin C on servo and the other end to a known good ground.
  15. With brake (and clutch) pedal in free position, check to see if servo pulls in full stroke. If not, go to step 18). If yes, remove jumper wire from pin E on servo. If servo stays at full stroke, check for proper operation of electrical connector at servo.
  16. If servo does not stay at full stroke position in step 15), remove the larger of the hoses to servo and plug orifice on servo. Reconnect the jumper wire to pin E until servo pulls in full stroke. Remove jumper wire from pin E.
  17. If servo does not stay at full stroke position, replace servo. If it does stay, check brake and/or clutch release valve adjustment. Check valves and hoses for leaks. Repair or replace as required.
  18. If servo did not pull in full stroke in step 15), remove the larger hose from the servo and plug the orifice. Check servo operation. If servo pulls in full stroke, check brake and/or clutch release valve for adjustment. Check for leaks in hose.
  19. If servo did not pull in full stroke, remove smaller vacuum hose from servo and check for vacuum. If vacuum is present, inspect connectors carefully for leaks. If okay, replace servo. If vacuum is not present, check connections between servo and vacuum source for leaks or incorrect connections.
scientia non olet · About LEMON Manuals