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Discussion Starter #1 (Edited)
Hi,

I have a problem with my car, 1996 Saab Ng900 turbo. When I turn on ACC the rpm of the engine decrease to 800 and even 750. Without the ACC the engine works at 950 - 1000 rpm.

I have read that the connector 1 of the IAC valve comes from pin 49 of the ecu. This one gives more "power" to the iac valve when AAC is on to keep the engine's rpm normal. The advise to test it, is using a test light:

-Turn ignition on, then off
-Connect test light between IAC connector terminal No. 1 and battery +
-Test light should come on
-Remove fuse No. 23
-Test light should faintly glow or not come on at all

Following this guide, test fails for the connector No 1.

I thoguht the original iac valve was the problem so I bought a new one but nothing changed.

272212


























272213


























Is there a way to fix it?

Thanks in advance for your help.
 

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Have you looked at the wiring diagram to learn the routing of that connection? The failed test suggests there's a break in that wire.
 

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Discussion Starter #6
Hello jvanbra and Mimmi,

Yes, I did it. Every thing seems to be ok, I even did a continuity test from IAC connector to ecu connector and there is no fault.

Is it possible that the ecu has failed?

I was reading a post at trionictuning dot com that in order to reset the computer to default, you have to take it off the car, not just cutting the energy from battery or unnpluging the connector, but phisically taking it out of where it is installed. At least 24 hours and it returns to default.

But I'm not so confident of doing so... but if the ecu went crazy by some mean, reseting to default could help.

272224
 

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To reset the ECU just disconnect the battery. Step on the brake pedal a couple times and everything discharges. No need to pull the ECU.
 

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Discussion Starter #13
Have you double checked (with multimeter) wire between IAC valve pin 1 and ECU pin 49?
Yes, twice.
I even used the multimeter instead of the test light to measure pin 1 of the IAC connector to battery (+). Multimeter showed 8 volts.
 

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I'd think it would be worth checking the battery supply to the ECM as well. A goofy system relay, for example, could cause low voltage through the whole system.
 

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Discussion Starter #18
I'd think it would be worth checking the battery supply to the ECM as well. A goofy system relay, for example, could cause low voltage through the whole system.
ok, that is something I'll do tomorrow, nothing to lose double checking it.
 
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