Hi everyone Im a newbie and love the site. I have a problem with the IAC , it does not show any voltage. Do I need to get a new pcm ?

 

Chase your wiring and check all your fuses before you go to the expense of a new PCM. I know it is time consuming but its worth the money you could save for a 50 cent fuse or wire connector. If you don't already have on go get a test light, 20 bucks at sears.

 

I traced the wires from the pcm to the IAC and it showed continuity . What fuses should I check. Thanks for the reply .

 

I would just check all of your fuses, without studying a wiring diagram I don't know for sure which one controls that function. If nothing else you might find a fuse that you didn't know was blown. It's just not a bad idea to be sure before you drop the big money on a computer then you have to take it to the dealership to have it flashed.

 

I checked all the fuses , all were ok. When I probe the purple/black wire + and the brown/white wire - there is no voltage but if I put the negative lead from the voltmeter to a ground I get 12 volts + . Should the voltage be that high ?

 

Are we talking about the Idle Air Control Motor here?

 

Im talking about the wires going to the idle air control motor.

 

According to the FSM (2001 yes?), there's 4 wires used in that circuit. 2+ and 2- ... it's a "stepper motor" ... it doesn't run ... it positions. The 4 colors are Gray/Red, Yellow/Black, Brown/White and Purple/Black. The PCM pulses the "motor" to various positions based on, among other things, engine coolant temperature and intake air temperature. You may not have a PCM or IAC problem. Garbage In - Garbage Out ... If one of the sensors is bad ...

Oh ... you don't show any voltage across those two wires for one of two reasons ... they either both have +12 on them (voltage is a DIFFERENCE in potential) or one has +12 and the other is open (because the PCM wants it that way). You have to read voltage from each wire to ground and the fact that a wire doesn't have a voltage on it at any given time in a digital circuit is meaningless.

What made you check voltage? What are your symptoms? Truck won't run?

 

make sure the 2 12V wires have 12V to ground, and the 2 12V neg wires have contiunuity to ground or atleast continuity between teh farthest ends of eachother...

 

I tested for voltage because the truck has a rough idle. The pintle on the IAC would not move so I bought a new one and that didnt help the idle problem. The Haynes manual said to check for voltage between the purple/black wire + and the brown/white wire - . Since there is no voltage I figured the pcm was bad. The computer has not thrown any codes but the IAC is not working , will not adjust idle when AC is on etc.