Ron D, P1605 fix vaccum lines I think, still get same code. Changed IAC still same code. Checked pulse as per your post. (If I did it right,,,) voltage low 2.?? Doesn't fluctuate much. Pierced the sensor wire connected voltmeter -- to needle and + to battery +. Was this correct? And if so is his telling me it needs PCM? Can I change it without computer programing? Thanks in advance.

 

Welcome to the forum

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Year of Ranger and engine model?

P1506 Idle Air Control Overspeed Error
Means the computer can not lower the Idle RPMs by closing the IAC Valve all the way
Can mean IAC Valve is stuck or there is an unknown air leak

After engine is warmed up and idling unplug the IAC Valves 2 wire connector
Idle should drop
If so then computer was setting the high idle, which could mean computer issue
If idle doesn't drop then IAC Valve is stuck or there is an unknown air leak

 

Ron D,,, I'm hoping I got it right far as internet,? I can't find any other vaccum leaks. Took a trip to get it to temp. Pulled the IAC harness, No idle drop at all. Their is a tube from the valve cover to the intake tube, I pulled that tube and the idle when down,,,don't know what it means just mentioning it. And it's a 96 ranger 2.3 4cyl. 8 plugs

 

That reads like the PCV systems Breather hose
Shouldn't effect idle, it just allows filtered air into the valve cover area because PCV Valve is pulling air out at the other end of valve cover