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Home >> Jeep >> 1998 >> Cherokee Classic, 2.5 P >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - Engine Performance >> Self-Diagnostic Tests >> Test TC-25A: Idle Air Control Motor Circuits

Test TC-25A: Idle Air Control Motor Circuits

NOTE: For connector terminal identification, see CONNECTOR IDENTIFICATION . For component location and wiring diagram, see WIRING DIAGRAMS article.
  1. On AB body, go to step 4)  . On all other bodies, ensure ignition is off for at least 10 seconds. Start engine and allow it to idle for 20 seconds. If engine will not idle, hold throttle slightly open to keep engine running. Go to next step.
  2. Using scan tool, actuate Idle Air Control (IAC) motor to 1400 RPM. If engine speed is not 1300-1500 RPM, go to step 10)  . If engine speed is as specified, go to next step.
  3. Using scan tool, actuate IAC motor to 900 RPM. If engine speed is not 800-1000 RPM, go to step 8)  . If engine speed is as specified, go to step 6)  .
  4. Using scan tool, read DTCs. If DTC SPECIFIC GOOD TRIPS counter is not displayed or displayed count is not "0", go to next step. If DTC SPECIFIC GOOD TRIPS counter is displayed and displayed count is "0", go to step 10)  .
  5. Using scan tool, read and record FREEZE FRAME data. Attempt to duplicate conditions in FREEZE FRAME data. Using scan tool, read DTCs. If DTC SPECIFIC GOOD TRIPS counter changes to "0", go to step 10)  . If DTC SPECIFIC GOOD TRIPS counter does not change to "0", go to next step.
  6. Condition required to set DTC is not present at this time. IDLE AIR CONTROL MOTOR CIRCUITS DTC sets if Powertrain Control Module (PCM) senses a short to ground or battery voltage on any of 4 IAC motor driver circuits while IAC motor is operating. PCM cannot detect an open circuit or stuck IAC motor. Possible causes are: grounded or shorted IAC motor wiring, defective connections, defective IAC motor or PCM. Go to next step.
  7. Check for defective wiring and connections at IAC motor and PCM. Repair wiring and connectors as necessary and perform TEST VER-2A: ROAD TEST VERIFICATION . If wiring and connectors are okay, go to next step.
  8. Start engine and allow it to reach normal operating temperature. Using scan tool, actuate IAC wiggle test. Engine speed should increase and decrease in accordance with scan tool display. If engine speed does not operate correctly, go to step 10)  . If engine speed operates correctly, go to next step.
  9. Wiggle wiring harness from IAC motor to PCM. If IAC motor stops operating while moving wiring harness, repair wiring as necessary and perform TEST VER-2A: ROAD TEST VERIFICATION . If IAC motor does not stop operating, see INACTIVE DTC CONDITION . Test is complete. Perform TEST VER-2A: ROAD TEST VERIFICATION .
  10. Using scan tool, stop all tests. Turn ignition off. Disconnect IAC motor connector. Inspect connector and terminals for damage. Repair connector and terminals as necessary and perform TEST VER-2A: ROAD TEST VERIFICATION . If connector and terminals are okay, go to next step.
  11. Using an external ohmmeter, check resistance between ground and IAC motor connector, driver No. 1 circuit (Gray/Red wire). If resistance is less than 5 ohms, repair short to ground in driver No. 1 circuit and perform TEST VER-2A: ROAD TEST VERIFICATION . If resistance is 5 ohms or more, go to next step.
  12. Check resistance between ground and IAC motor connector, driver No. 2 circuit (Yellow/Black wire). If resistance is less than 5 ohms, repair short to ground in driver No. 2 circuit and perform TEST VER-2A: ROAD TEST VERIFICATION . If resistance is 5 ohms or more, go to next step.
  13. Check resistance between ground and IAC motor connector, driver No. 3 circuit (Brown/White wire). If resistance is less than 5 ohms, repair short to ground in driver No. 3 circuit and perform TEST VER-2A: ROAD TEST VERIFICATION . If resistance is 5 ohms or more, go to next step.
  14. Check resistance between ground and IAC motor connector, driver No. 4 circuit (Violet/Black wire). If resistance is less than 5 ohms, repair short to ground in driver No. 4 circuit and perform TEST VER-2A: ROAD TEST VERIFICATION . If resistance is 5 ohms or more, go to next step.
    NOTE: Voltage may switch or remain constant in steps 15)-18).
  15. Reconnect IAC connector. Start engine and allow it to idle. Disconnect IAC connector. With engine still running, use an external voltmeter to check voltage on IAC motor connector, driver No. 1 circuit (Gray/Red wire). If voltage is not more than 5 volts at any time, perform TEST TC-25B: IDLE AIR CONTROL MOTOR CIRCUITS . If voltage is more than 5 volts at any time, go to next step.
  16. Check voltage on IAC motor connector, driver No. 2 circuit (Yellow/Black wire). If voltage is not more than 5 volts at any time, perform TEST TC-25C: IDLE AIR CONTROL MOTOR CIRCUITS . If voltage is more than 5 volts at any time, go to next step.
  17. Check voltage on IAC motor connector, driver No. 3 circuit (Brown/White wire). If voltage is not more than 5 volts at any time, perform TEST TC-25D: IDLE AIR CONTROL MOTOR CIRCUITS . If voltage is more than 5 volts at any time, go to next step.
  18. Check voltage on IAC motor connector, driver No. 4 circuit (Violet/Black wire). If voltage is not more than 5 volts at any time, perform TEST TC-25E: IDLE AIR CONTROL MOTOR CIRCUITS . If voltage is more than 5 volts any time, go to next step.
  19. Turn ignition off. Disconnect Powertrain Control Module (PCM) connectors. Inspect connectors and terminals for damage. Repair connectors and terminals as necessary and perform TEST VER-2A: ROAD TEST VERIFICATION . If connector and terminals are okay, go to next step.
    NOTE: Steps 20)-23) check for short circuits between IAC motor driver circuits.
  20. Using an external ohmmeter, check resistance between IAC motor connector, driver No. 1 circuit (Gray/Red wire) and each remaining circuit on IAC motor connector. If resistance is less than 5 ohms between any 2 circuits, repair driver circuits that are shorted together and perform TEST VER-2A: ROAD TEST VERIFICATION . If resistance is 5 ohms or more on all IAC motor driver circuits, go to next step.
  21. Check resistance between IAC motor connector, driver No. 2 circuit (Yellow/Black wire) and each remaining circuit on IAC motor connector. If resistance is less than 5 ohms between any 2 circuits, repair driver circuits that are shorted together and perform TEST VER-2A: ROAD TEST VERIFICATION . If resistance is 5 ohms or more on all IAC motor driver circuits, go to next step.
  22. Check resistance between IAC motor connector, driver No. 3 circuit (Brown/White wire) and each remaining circuit on IAC motor connector. If resistance is less than 5 ohms between any 2 circuits, repair driver circuits that are shorted together and perform TEST VER-2A: ROAD TEST VERIFICATION . If resistance is 5 ohms or more on all IAC motor driver circuits, go to next step.
  23. Check resistance between IAC motor connector, driver No. 4 circuit (Violet/Black wire) and each remaining circuit on IAC motor connector. If resistance is less than 5 ohms between any 2 circuits, repair driver circuits that are shorted together and perform TEST VER-2A: ROAD TEST VERIFICATION . If resistance is 5 ohms or more, replace IAC motor and perform TEST VER-2A: ROAD TEST VERIFICATION .
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