Chrysler Repair: 02 Neon: Engine revs high/code P0508, neon sxt, passage way

Question
QUESTION: I changed the headlights in a 2002 neon sxt 2.2. required removing airbox for left light. when completd I went to start the car and it reved at very high rpm, then surged, I cannot find anything unplugged. the throtle cable and speed control cable seem fine. I'm baffled. I have done this operation many times on several different neons and never had this happen. any help would be appreciated.

Thanks Jim

ANSWER: Hi Jim,
I don't see any relationship, so it may be co-incidental. Try for fault code readout with the ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see the mileage reading change instead to show four digit nubmers preceeded by a P. Let me know those and we'll see if they are related to the problem.
Roland
PS: Sorry for the delay but I just found your question in the 'pool'.

---------- FOLLOW-UP ----------

QUESTION: Hi Roland,
The only code that came up was P0508. I hope that can shed some light on the problem.

Thanks, Jim

Answer
Hi Jim,
The code is consistent with your observed problem: 'idle air control sense circuit current is low (less than 175 mA)'. While I don't have a manual for the '02 Neon 2.2 sxt or for any vehicle with that exact engine, my suggestion would be to check the harness/plug of the iac motor mounted in the side of the throttle body, looking all along it from the plug to where it joins the main harness for possible heat damage to the insulation of the wires which may cause a short to voltage or a short to ground.
If that looks ok, then I would remove the iac motor and check for dirt/damage to the tip of the valve and to be sure the passage way is clean for the side air and for the tip the valve where it meets the passageway area. The 'motor' is really just a moving valve stem that opens and closes the idle air passageway.
While there, you would do well to clean the throat, butterfly plate, and idle air side-passageway as gum in that area can play havoc too.
Because I don't have the specific manual, I can mention that the 4 cyl 2.0/2.4 motor has 2 wires only and they are probably connected to pins 28 (brown/violet) and 38 (violet/gray) of the pcm. You could check continuity of those.  
Roland

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