LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Oldsmobile >> 1998 >> Regency >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0507 - IAC System Rpm High >> Diagnostic Procedures
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Using scan tool, read DTCs. If any other DTCs are set, diagnose affected DTCs before proceeding. If no other DTCs are set, go to next step.
  3. Start engine. Turn all accessories off. Using scan tool, monitor ENGINE SPEED and command engine speed up to 1500 RPM, down to 500 RPM, and up to 1500 RPM. If ENGINE SPEED remains within 100 RPM of desired RPM for each command, see DIAGNOSTIC AIDS. If ENGINE SPEED is not as specified, to next step.
  4. Disconnect IAC harness connector. Install IAC Node Light (J 37027) in IAC harness connector. Monitor node lights while commanding engine speed up to 1500 RPM, down to 500 RPM, and up to 1500 RPM. Both node lights should cycle Green and Red, but not OFF as RPM changes from 500-1500 RPM. If lights flash as specified, go to step 6). If lights do not flash as specified, go to next step.
  5. Check IAC "A" high and low, and "B" high and low circuits for open, short to voltage or short to ground. Repair as necessary. After repairs, go to step 11). If circuits are okay, go to step 9).
  6. Check for vacuum leaks. Ensure throttle stop screw has not been tampered with. Check for throttle plate or shaft binding. Check accelerator and speed control cables for misadjustment or binding. Check for faulty, missing or incorrectly installed PCV valve. Repair as necessary. After repairs, go to step 11). If no problem is found, go to next step.
  7. Check for faulty connection at IAC harness connector. Repair as necessary. After repairs, go to step 11). If connection is okay, go to next step.
  8. Replace IAC valve. After replacing IAC valve, go to step 11).
  9. Check for faulty connection at PCM harness connector. Repair as necessary. After repairs, go to step 11). If connection is okay, go to next step.
  10. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  11. Start engine. Turn all accessories off. Using scan tool, monitor ENGINE SPEED and command engine speed up to 1500 RPM, down to 500 RPM, and up to 1500 RPM. If ENGINE SPEED remains within 100 RPM of desired RPM for each command, repair is complete. If ENGINE SPEED is not as specified, return to step 2).
scientia non olet · About LEMON Manuals