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Home >> Isuzu >> 1996 >> Hombre S >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Testing >> DTC P0506 - IAC System Rpm Low >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Ensure engine is at normal operating temperature, transmission is in Park or Neutral, parking brake is set and A/C is off. Using scan tool, command IAC valve from 900 to 2000 RPM. If engine RPM changes smoothly, go to next step. If engine RPM does not change smoothly, go to step 5).
  3. Turn ignition off. Disconnect IAC valve connector. Remove IAC valve. Measure resistance between IAC "B" high and IAC "B" lo circuit terminals at IAC valve. Also, measure resistance between IAC "A" high and IAC "A" lo circuit terminals at IAC valve. If each reading is 40-80 ohms, go to next step. If one or both readings are not 40-80 ohms, go to step 13).
  4. Measure resistance between IAC "B" high and IAC "A" lo circuit terminals at IAC valve. Also, measure resistance between IAC "A" high and IAC "B" lo circuit terminals at IAC valve. If each reading is infinite, go to step 15). If one or both readings are not infinite, go to step 13).
  5. Turn ignition on, with engine off. Disconnect IAC valve connector. With test light connected to ground, probe all 4 terminals at IAC valve harness connector. If test light turns on for 2 terminals, go to next step. If test light does not turn on for 2 terminals, go to step 7).
  6. With test light connected to positive battery terminal, probe all 4 terminals at IAC valve harness connector. If test light turns on for 2 terminals, go to step 8). If test light does not turn on for 2 terminals, go to step 9).
  7. Check for an open or short to ground in IAC valve lo and high circuits. Repair as necessary. After repair is completed, go to step 15). If circuits are okay, go to step 10).
  8. Start engine and allow it to idle. With test light connected to ground, probe all 4 terminals at IAC valve harness connector. If test light flashes on and off for all 4 terminals, go to step 11). If test light does not flash on and off for all 4 terminals, go to step 12).
  9. Check for an open or short to voltage in IAC valve lo and high circuits. Repair as necessary. After repair is completed, go to step 15). If circuits are okay, go to next step.
  10. Check PCM connector for poor terminal connections. Repair as necessary. After repair is completed, go to step 15). If connector is okay, go to step 14).
  11. Inspect IAC valve passages. Repair as necessary. After repair is completed, go to step 15). If IAC passages are okay, go to step 13).
  12. If test light remained on constantly for terminals that did not flash in step 8), go to step 9). If test light did not remain on constantly for terminals that did not flash, go to step 7).
  13. Replace IAC valve. After repair is completed, go to step 15).
  14. Replace PCM. Program replacement PCM using required equipment. After repair is completed, go to next step.
  15. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function then enter DTC P506. If scan tool indicates TEST RAN AND PASSED, go to next step. If scan tool does not indicate TEST RAN AND PASSED, repeat step 2).
  16. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, no problem is indicated at this time. See DIAGNOSTIC AIDS.
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