P0509-IDLE AIR CONTROL VALVE SENSE CIRCUIT HIGH





For a complete wiring diagram Refer to Section 8W.


  • When Monitored:

    Engine running. Battery voltage greater than 10 volts. IAC motor operating.

  • Set Condition:

    The PCM senses a short to ground or battery voltage on any of the Linear Idle Air Control (LIAC) control circuits for 2.75 seconds while the IAC motor is active. One Trip Fault. Three good trips to turn off the MIL.


Possible Causes
  
(K961) IAC RETURN CIRCUIT SHORTED TO BATTERY VOLTAGE
  
(K61) IAC CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE
  
(K61) IAC CONTROL CIRCUIT SHORTED TO THE (K961) IAC RETURN CIRCUIT
  
IAC MOTOR
  
PCM
  

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1.IAC MOTOR OPERATION

NOTE: If the engine will not idle, maintain an engine speed between 800 and 1500 RPM.






Is the IAC Current above 999 mA?

Yes
  • Go To 2


No

2.IAC MOTOR






Does the scan tool display IAC Current at 0 mA?

Yes


No
  • Go To 3

3.(K961) IAC SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE








Is the voltage above 0.5 of a volt?

Yes


No
  • Go To 4

4.(K61) IAC CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE





Is the voltage above 0.5 of a volt?

Yes


No
  • Go To 5

5.(K61) IAC CONTROL CIRCUIT SHORTED TO THE (K961) IAC RETURN CIRCUIT






Is the resistance below 5.0 ohms?

Yes


No
  • Go To 6

6.PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.




Were there any problems found?

Yes


No