DTC P0506 - Idle Control System Low Rpm

Perform On-Board Diagnostic (OBD) System Check. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
Using scan tool, read DTCs. If any other DTCs are set, diagnose them first before proceeding. If no other DTCs are set, go to next step.
Start engine. Turn all accessories off. Using scan tool, monitor ENGINE SPEED and command engine speed up to 1500 RPM, down to 650 RPM, then back up to 1500 RPM. If ENGINE SPEED remains within 50 RPM of desired RPM for each command, check for an intermittent problem. See TESTS W/O CODES article. If operation is not as specified, go to next step.
Disconnect IAC harness connector. Install IAC Noid-Light (J37027A) in IAC harness connector. With engine running, monitor noid-lights while commanding engine speed up to 1500 RPM, down to 500 RPM, then back up to 1500 RPM. Both noid-lights should cycle Green and Red, but not OFF as RPM changes from 500-1500 RPM. If noid-lights flash as specified, go to step 6). If noid-lights do not flash as specified, go to next step.
Check IAC "A" high and low and "B" high and low circuits for an open, short to voltage or short to ground. If a problem is found, repair as necessary. Retest system. If no problem is found, go to step 9).
Ensure throttle stop screw has not been tampered with. Check for stuck IAC valve or throttle linkage. Check for restrictions, collapse or blockage in air intake system. Check throttle body bore and IAC valve for excessive deposits. If a problem is found, repair as necessary. Retest system. If no problem is found, go to next step.
Check for faulty connection at IAC valve harness connector. If faulty connection is found, repair as necessary. Retest system. If connection is okay, go to next step.
Replace IAC valve. Retest system.
Replace PCM. Retest system.