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Discussion Starter · #1 ·
Hello,

I really need some help with my 2005 Saab 9-3. A few months back my CEL came on and I noticed the the acceleration was not as strong, with the turbo indicator maxing out well before the red line.

The mechanic scanned it and said that T8 P033-00 came up, indicating a problem with the charge air bypass valve. He reset the computer without fixing it and for the next few days the CEL stayed off and the acceleration was great. However, the CEL and acceleration went off again. I took it back to him and he checked all the hoses and said that I need to by and replace the charge air bypass valve on the turbo.

Apparently, there is another similar valve on one of the hoses from the turbo, but he was sure that the one on the turbo was the problem so I agreed that he replace it (even though it cost ~$500). When he was done, he reset the computer and once again, after an hour, the CEL came back on and the acceleration dropped.

I am taking it back to him to figure the problem out but I was wondering if anyone else knew what the problem might be? I find it very weird that the acceleration is temporarily restored when the computer is reset.

Thanks.
 

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I will offer some advice...base on what u have said:

-resetting ECM is electrical
-replacing bypass valve is mechanical

a mechanical failure will still be there even if u reset the ECM, I doesn't go anywhere, it's broke it's broke...now a electrical will not go away by replacing a mechanical valve...while replacing the valve would be logical with that code, but if resetting the ECM temporarly fixes the problem, without doing anything mechancal, than u problem is not mechanical
 

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Based of ur symtoms I sounds like ur bpv is stuck slightly open, that's all I can hink of for not building boost and getting that code. Follow the bpv hose, check for cracks/kinks, follow it to, if applicable, the sensor it's connected too. That could be the problem....



Ps: that's advice, not 100% guaranteed to be ur issue but a good place to start
 

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This a 2.0T or 2.8t? I will check WIS when I get a chance and see...
 

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Discussion Starter · #7 ·
Jn2, it is a 9-3 2.0t...

ctrlz, I have already replaced the bypass valve that is mounted to the turbo. Maybe the one that is on the hose leading from the turbo that need replacement?
 

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If you have replaced the valve, then it is either the solenoid or one of the three hoses connected to the solenoid. Electrical connection to the solenoid also a possible source, but not as likely.

The solenoid switches its output between vacuum (the very short hose) and positive pressure. The vacuum side of the circuit is used to pull open the bypass valve. That would not give the performance loss symptoms you describe. I believe your problems lie with the positive pressure aspect of the circuit, which is used to keep the bypass valve shut. The photos in post #'s 2 & 3 in the above mentioned thread show those lines.

If you have replaced the vac line between the solenoid and the bypass valve, your next bet is to replace the line from the intake to the solenoid. Relatively easy access to this line for a do-it-yourselfer. If that does not do it I would swap out the solenoid.

You might be able to check the vac line in question with the car at idle. Rub your fingers in a bit of liquid dish detergent and water then rub the vac line. Maybe you can get it to bubble at the leak. Never tried it but should work.
 

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Discussion Starter · #9 ·
ctrlz,

In your 8th post in the quoted thread, I think you show a close-up of the CBV. That little box on top of it, is that the sensor/controller of some sort that may be my problem?
 

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ctrlz,

In your 8th post in the quoted thread, I think you show a close-up of the CBV. That little box on top of it, is that the sensor/controller of some sort that may be my problem?
This post shows the boost control solenoid:
http://www.saabcentral.com/forums/showpost.php?p=777860&postcount=8

My finger on bypass solenoid here:
http://www.saabcentral.com/forums/attachment.php?attachmentid=2206&d=1120305068
The positive pressure line from the intake is running off to the right under the large radiator hose.

These solenoids are same part number, I believe. Solenoids are valves controlled by electric current. In this case they are controlling the flow of air. It is easy to imagine the valve being turned completely on or off by a switch. But the car can also turn it on and off rapidly by pulsing the electricity so that it functions like a partially opened valve. This switching frequency is called the duty cycle of the solenoid.

Solenoids are finicky things when they fail. Often failure is temperature dependent, meaning they tend to stick when hot or cold. There is no set rule, just erratic behavior. I think the small solenoid in question here runs about $30.

With the symptoms you have you won't be able to prove the solenoid you removed was bad. Only time and lack of recurring problems will confirm that.
 

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Discussion Starter · #11 ·
So the mechanic got another charge air bypass valve and the problem returned in 2 days. Looks like that wasn't the problem. I'm going to have him try the solenoid as you suggested ctrlz. A sticking valve as you said sounds very probable.

Jn2, did you happend to look that sensor up???

Thanks again guys...
 

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Well I just read the WIS...
p0033 indicates a failure of the bypass to open. This is detected when the throttle is released under moderate acceleration. The vacuum side of the circuit should open the bypass at this point under normal operation. If the system fails to detect a drop in charge air pressure, it presumes a fault in the bypass function. The sensor involved here is the intake pressure sensor, and its function is not limited to reporting on the bypass status. The intake pressure sensor is located to the right of the throttle body motor as you face the engine.

So the bypass valve is probably not getting vacuum properly applied to its port. Still the likely culprit is the solenoid not switching from positive pressure source to vacuum source.
This picture shows the short hose which is the vacuum source for the bypass circuit. About 1" to the right of my thumb you can see where the short tube is attached to the intake. It makes a 90 degree bend curving up and toward you in the photo to enter the solenoid. The whole tube is maybe 2.5" long.
http://www.saabcentral.com/forums/attachment.php?attachmentid=2209&d=1120305272
 
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