This is my first post in this forum and any help anyone can offer would be much appreciated! I recently purchased a 2004 9-5 Aero. When I bought the car, the catalytic converter was plugged so I purchased a used replacement from Goldwing's. The car is now breathing and running much, much better. I also replaced both oxygen sensors at the time of installation of the catalytic converter and cleared all codes to shut the check engine light off.

Since then, about a month has passed. The check engine light will stay off for about a week and then reappear saying oxgen sensor 1 bank 1 no activity. I have replaced the sensor 3 times as it comes with a 1 year warranty. I used an OE Bosch the first time and an OE NTK the last 2.

It definately has me frazzled. My logic now is that whatever ruined the old catalytic converter is probably ruining my upstream oxygen sensor now. A co-worker of mine is an ASE certified technician and is baffled by this as well.

The question I have is, what do I try next? Obviously, I don't want to have to change the o2 sensor every week and I want to get to the bottom of the problem. Any suggestions??

Thanks!

Adam Robison
Fort Wayne, IN

Check for vacuum leaks, cracked, rotted lines. It will run rich if you have a leak after the maf in the intake system.

Firstly, it is not legal to sell used cat converters.

And B, just cause you are getting an 02 sensor code doesn't mean that is the problem. I argued with an audi buddy for a month untill he finally got a good used maf.

Well since I didn't sell it I feel safe. I have checked for vacuum leaks and everything looks fine there. I did replace a couple questionable vacuum hoses and reset the light. Stayed off for about 2 minutes.

I understand it doesn't necessarily mean o2 sensor. How can I check the MAF? Is there some sort of test I can perform?

Thanks for any further help you can offer!

I meant to post a couple of days ago, but your MAF may be your problem. The MAF communicates with your O2 sensors to control fuel / air mixture. The MAF is extremely difficult to test. You can find some videos regarding the procedure on youtube, although the videos are not Saab specific. I saw a cable program recently, "two guys garage" where they discuss the MAF in great detail and a faulty one turned out to be the cause of a rough running issue. I think it's easier to just swap it out to see if that cures the issue.

I went ahead and ordered a new Mass Air Flow Sensor. I will install it tomorrow and see if that cures the issue.

On a separate note, I did notice an oil leak on the backside of the head, presumably from the head gasket as its hard to tell. I read on here that re-torques cure most of these issues, is this true in everyone's opinion? I purchased 10 new head bolts and a new valve cover gasket as well. I figured it couldn't hurt anything to try before I drop a thousand dollars on a head gasket repair.

I'll keep everyone updated and I much appreciate the assistance!

Adam

Originally Posted by Adam Robison

I went ahead and ordered a new Mass Air Flow Sensor. I will install it tomorrow and see if that cures the issue.

On a separate note, I did notice an oil leak on the backside of the head, presumably from the head gasket as its hard to tell. I read on here that re-torques cure most of these issues, is this true in everyone's opinion? I purchased 10 new head bolts and a new valve cover gasket as well. I figured it couldn't hurt anything to try before I drop a thousand dollars on a head gasket repair.

I'll keep everyone updated and I much appreciate the assistance!

Adam

One typical leak point on these cars is the oil pressure switch or sensor. The only run about $20, but are a bit difficult to get to as it is behind the starter on the back side of the block. It's the first thing I thought of when you described where your oil leak was. I have one on order right now, and I don't even know where my oil leak is coming from, it's just such a common issue, it's the first thing I'm going to try. btw, I've already done my head gasket & fresh cylinder head gasket.

Today I installed all new head bolts and torqued them down hoping to stop the head gasket leak. I also installed a new mass air flow sensor. My check engine light stayed off for about 3 start cycles before-re-illuminating. I have checked for vacuum leaks, replaced oxygen sensors and now the mass air flow sensor. What else can it be?

Also, when I went to clear the code this time I noticed it had thrown a new code as well, P 1141 (OS2 Heater Circuit, Current too low, sensor 2). Does anyone happen to have an 02 sensor wiring diragram for a 2004 9-5 aero I can get a copy of? Thanks

Make sure the check valve between your PCV outlet and the throttle body is connected and working, (there's an arrow on the body of the check valve to indicate flow direction), I found mine disconnected and it was throwing a code. Sounds like your heated O2 sensor is defective or wired incorrectly, ( did you wire in a cheap universal O2 sensor?) sorry, but don't have a wiring diagram.

Thanks photousa, I will check the valve this weekend to make sure it is functioning and connected. I did not use a universal o2 sensor. It is an OE type NTK (also tried a Bosch as well). The weird thing is, I cleared the code before I left work last night and it has remained off. Its been driven about 50 miles now without re-illuminating. I have access to scan tools and we can watch the 02 sensors functioning properly. Its like something triggers the O2 sensors to freeze up and then the code is thrown. We have witnessed it freezing with the scan tool. Its not something that happens continuously, making it very difficult to isolate.