The blower truck has received a cable throttle body and we
are trying to make it work using the original electric throttle
PCM ('04 Silverado SS) and a '06 Express van OS. Things are
working somewhat, with notable exception of the IAC. The
mechanic has inserted the pins and wired up to the "unused"
4 pins on the connector. But we see zero electrical activity.
I am suspecting maybe the PCM simply does not have IAC
drivers (GM would save dimes, right?). Van and SIlverado
PCMs show different part numbers. Van has options for cable
and electric throttle (JL4).

Anybody know whether my suspicion is right, that electric
throttle PCMs deleted the IAC motor drive circuitry? Or do I
have to look elsewhere for why all 4 pins are nothing but
millivolts of noise?

'03-'07 Silverado SS PCM P/Ns 12576106, 12582605, 12586242,
12586243

'06 Express PCMs 12589462, 12602801 (not sure which is the
desired non-JL4)

I also see some weird little dust-bunnies from trying to push the
van OS onto the Silverado PCM and then applying a custom OS.
That's potentially a 3-way clusterphuq although at least it is
running. Things like the fueling being off by 50% although the
custom OS seemed to "take" - but which version, truck or van,
who can say? Seems to go by VIN and not hardware. We're
going to try a van OS and a brand new van PCM and see how that
goes. Just have to do without the righteous truck body VIN (at
least until all else is working right).

Now I also wonder which is closer, engine harness wise - an '02
Silverado cable throttle, or an '06 van cable throttle. The PCMs
look to be closer, '04-'06, but if everything from the connector
back is closer truck-truck then that's another, and cheaper /
more plentiful option. Not too many differences, but some, between
truck and van connector pin-outs. No idea about '02 - '04 diffs.

 

Several of the Blue/Green PCM's don't have IAC drivers in them. I've never cataloged it by service number but the ones from vans and GTO's always have IAC drivers in them, the others don't.

For the harness, one from an 06 van will be a better match for a Blue/Green PCM. There are a few differences, but the main one is the difference in how the O2 sensors are grounded between the Blue/Red and the Blue/Green PCM's.

 

an 02 vette pcm should have the IAC drivers, right?

 

Yes. All of the Blue/Red PCM's have IAC drivers.

 

find a pcm blue green that the serv number ends in 1565. that will work with the iac.