P0505 OBDII

Some noid light kits have noids that will plug into the connector and flash if the circuit is working, If the engine is running and you unplug the IAC what does the idle do? I think at this point you need a better scanner or a more competent mecahnic. You need to know if the MAP sensor is reading accurately, the TPS etc, Just because it's an IAC code doesn't mean the IAC is faulty, it means that it's trying to control the idle and something is keeping the engine from idling at the proper speed. If the noid light flashes or the idle speed changes when the IAC is disconnectted then the PCM isn't likely the problem. Here's a simple idea, check for any blown fuses that say IAC,
THe IAC, MAP sensor, TPS etc are all wired onto the ASD circuit. ASD stands for auto shutdown, It essentially is the relay that the pcm uses to know when the engine is running so any problem or failled circuit or sensor on it can cause all kinds of weird codes and the symptons you are describing. The reason I keep saying TPS is because if it's signal is erattic the IAC keeps adjustting for it.

You need to have this properly diagnosed or at the very least get a wiring diagram and start to check for this short. If you want to try one more hail mary part buy the TPS from the dealer and install it. Be sure the throttle body gasket isn't leaking as well


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