DTC P0507: Idle Control System Rpm Higher Than Expected

NOTE: If any trouble codes are set besides DTC P0506, P0507, P0171, P0172 or P0300-P0304, diagnose them first.

Ensure electrical wiring, emission control hoses and air cleaner are all okay. Turn ignition on. Turn off all accessories. Ensure ignition timing is set properly. Run engine to normal operating temperatures.
If scan tool is not being used, locate test connector in relay/fuse box in engine compartment. Connect fused jumper wire between test connector terminals "B" and "D". See Figure . Using scan tool or frequency monitor, check Idle Speed Control (ISC) output frequency. If engine RPM is not within specification, go to next step. If engine RPM is within specification, check for an intermittent problem. See TESTS W/O CODES article.
Perform testing procedure in DTC P0505 , steps 1) and 2). Follow DTC P0121 , steps 1) and 2) (if necessary). If DTC P0507 was set, go to next step. If DTC P0506 was set, ensure frequency measured in step 2) is more than 40 percent. If frequency is as specified, perform testing procedures in DTC P0300 -P0304. If frequency is not as specified, replace PCM. Retest system.
Ensure frequency measured in step 2) is less than 20 percent. If frequency is as specified, check for vacuum leaks in emission control hoses and intake system. If frequency is not as specified, check ECT sensor. See SYSTEM/COMPONENT TESTS article. If ECT is okay, replace PCM. Retest system.