IAC Voltage

[Travis Messenger]

I'm trying to diagnose my intemittent idling problem (stalling and racing idle). According to Haynes, the input voltage (key on engine not running) to the IAC is 10.5 to 12V. Mine is reading about 4-5V. Does this indicate that something is wrong with my PCM or is Haynes wrong. Also the resistance of the IAC is 0 ohms, which is not what the Haynes manual says it should be.
I'm not sure what to check or replace next. Hopefully not the PCM. The IAC is less than a year old. I got it from NAPA, and I remember the guy telling me that there were two available for my X. Now I'm not sure I got the right one. Thanks for any help you can give me.

Travis

 

[KPT]

Haynes is wrong, input voltage is 5V. Check the other wire with the key on engine off, optimal voltage is .96V

 

[Rhett]

That's TPS voltage...IAC is Idle Air Control valve, and I'm at work and don't have my manual in front of me to check, but it's not the same as TPS voltage...

 

[KPT]

Oops yeah, brainfart. I have no clue why I read IAC as TPS.

 

[Travis Messenger]

Has anyone found any info on this subject.
Thanx

 

[dogfriend]

I have a butt load of info for a 97...you didn't say what year your X is...hope this is useful:

 

[dogfriend]

iac2

 

[dogfriend]

iac3

 

[dogfriend]

iac4

 

[dogfriend]

iac5

 

[dogfriend]

iac6

 

[dogfriend]

iac7

 

[dogfriend]

iac8

 

[dogfriend]

iac9

 

[dogfriend]

iac 10 The schematic for the IAC circuit. VPWR is the red (R) wire.

 

[Opera House]

Thanks for clearing the diode issue up

I'd been warning people who test these on a bench that they should be concerned about polarity. A lamp in series with the power will protect the diode in case they hook it up backwards. Otherwise the diode makes it a short and it burns up. Older manuals indicated an internal diode and later ones just showed the coil. Never got around to testing my 97 to see if the diode was there. Since this is a pulsed output, some digital meters may not read the voltage correctly. This is one case where an analog meter works better.