Cadillac P1509: Idle Speed High - IAC System Not Responding

What Does The Cadillac P1509 Code Mean?

Conditions for setting the DTC:

• DTC P1370, P1371, P1406, P1441 and P1442 not set
• Engine started, vehicle not moving
• ECT sensor from -4ºF to 230ºF
• BARO sensor over 65 kPa
• Engine runtime over 10 seconds in closed loop
• MAF sensor from 2-35 g/sec

What Are The Potential Causes Of The Cadillac P1509 Code?

Below are some potential causes of this DTC:

• Base engine problem (engine vacuum leak or PCV valve leak)
• Fuel system is too rich or too lean
• IAC motor circuit open, shorted to ground or shorted to power
• Throttle body adjustment screw tampered with or damaged

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> WORKPRO 582-piece Crimp Terminals, Wire Connectors, Heat Shrink Tube, Electrical Repair Kit
>>> GM Genuine Parts 17113598 Fuel Injection Idle Air Control Valve
>>> HOWYAA HVE72A Electronic Fuel Injection Throttle Body Assembly for 07-11 Cadillac

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Reference Sources

GM, 2013, Service Bullettin – Prior To Any Circuit Testing.