Idle Air Control Valve not responding

[MegaSlant6]

Hello, have a MS3 Pro installed on a car currently set up for drag race only, due to a couple of things going on, do not get the car out as much as I would like to.

Got the car out to a track this past weekend, first time since last July, noticed that the idle air control valve on the GM Vortec throttle body was staying open maybe 10 to 15 percent with the motor warm. When I did the initial MS3 Pro install in May of 2016 I went through the set up and verification process of the IAC and observed the valve opening closing,,,now it does not react at all.

Went to the Can / Bus Test Mode section,, there the two gauges shown on the screen sweep full scale when I select in - out testing but the actual IAC valve does not move, with the engine off or running.

I went back through the wiring
wire 31 to D
wire 30 to C
wire 33 to B
wire 32 to A

checked continuity and resistance for each wire from the IAC connector back to the MS3 wire harness connector,, all was good. Checked the OHMs resistance of the IAC that was installed, it was good, tried a new IAC that I had on the shelf,, still no response.

could I have inadvertently changed something in the MS3 Pro that shut off the IAC valve? Although I do not think so as the test mode indicates a signal is being sent...

In section 6.1.1.3, it is mentioned to increase the time step size, it was set on 6, at the initial install and last year it worked at that level, I bumped it up to 25 ( the max value) and still no response.

so can I check for voltage out at the A B C D connector pins while the system is in the Cab / Bus Test Mode? If so what voltage would I be looking for and would I be looking a voltage across D to C and B to A, My IAC follows the path shown on the middle IAC diagram shown in section 4.7.1

ideas on nest steps?

[AlanJ]

Does the iac valve make any noise or wiggle like it's trying to move?

Disconnecting the mspro and using a volt meter on the pins connected to the iac do you get the same resistance as if you do on the iac itself?

Sent from my Z833 using Tapatalk

[MegaSlant6]

the IAC has no movement, vibrations,,

and I have not tried

Disconnecting the mspro and using a volt meter on the pins connected to the iac do you get the same resistance as if you do on the iac itself?

but I will,

thanks

[MegaSlant6]

using my multi-meter and measuring resistance from the MS ECU connector to the IAC valve I get the the same resistance as when checked directly on the IAC valve connection.
I get 45.9 to 46.8 ohms, I realize that is slightly above the 35 to 45 that is stated in the manual, probably due to the accuracy of the multi-meter that I am using. The values are repeatable.

I then reconnected the ECU connector, disconnected the IAC connector and put the MS in IAC test mode at the can/bus test mode page, set the multi-meter to 20 V DC and checked for voltage across A & B and C & D,, there is no voltage reaching the IAC, as continuity and resistance through the harness checked OK, the issue is the MS ECU is not sending a signal to the IAC,

that leads me to believe that either there is a failure in the ECU or I switched off the IAC / fuel enrichment, and don't remember or know how to turn it back on..

I'll get a copy of my tune and post it here,,,,,

[MegaSlant6]

TunerStudio MSv3.0.22

Firmware 1.3.4 20150123

MSQ is posted below, issue seems to be that the MS ECU is not sending a signal to the IAC valve with the engine in operation or in can bus testmode.

[billr]

Change the IAC control from "moving only" to "always on", or at least "holding". That way, voltages on the driver pins should show when the stepper isn't moving, when you make "static" checks.

[MegaSlant6]

"always on"

I did that previously, that did not make the valve respond - move,, I can set that configuration back in and see if any voltage shows at the IAC.

[MegaSlant6]

I can set that configuration back in and see if any voltage shows at the IAC.

just did that, and at the can / bus test mode screen did the:

always moving, home and the other test,,

no voltage at the IAC connector, and there I am looking for voltage across pins

A and B and then C and D , as it is marked on the GM IAC connector

[jsmcortina]

Contact your supplier (DIYAutoTune) for assistance.

James

[MegaSlant6]

Contacted DIYautotune and the issue is resolved. They were great to work with, I am very satisfied with the product support.

[lsxfox]

i have the same issuse. mind posting the fix? thanks.