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Discussion Starter #1
As I have to go a far distance to get a reading for my Saab 93-I with Tech 2 my question is:
Suddenly it appears "check engine". As the engine drive like a cat without any disturbances, it starts immediately, acceleration is ok. Now what can it be?
1. One of the sensors?
2. Lambda Sensor? Bosch Motronic?
Bill
 

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I had/have the same issue. I got a Tech2 reading and the garage came back with "ignition problem". But as in your case I see absolutely no problems.
I have now left this alone for 2 years with no ill effects! I can clear the CEL by pulling a fuse for a while, but it comes back.

Recently a friend told ne he had a similar issue with another GM car (I guess like my car yours runs the Bosch not Saab management system), and even though it came up as ignition, he fixed it when he changed he lambda sensor. I will get round to trying it soon...
 

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Hello Alpenflitzer with out having the codes read then it's all a guessing game .
Is there a local garage with a code reader ? Dose not have to be tech 2 .
Most modern garages with a good code reader can pull codes .
I have a 2008 9-3 and I use a local garage for any diagnostic work on mine , no problems .
Or for starters disconnect the battery for an hour and try again, could be that the car had a wobble .
Like all cars with a check engine lights it's telling you it has a problem .
 

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A code reader can be had for very short money... about $50 USD gets one that will tell you the codes and/or the ready state of the monitors. A Tech II is a lot more money (Chinese clones are $300+) but you don't need that to check a CEL.
 

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Discussion Starter #5
Problem solved! The coolant temperature sensor and the Lambda sensor were faulty. The coolant sensor told the electronic to provide more fuel whereas the Lambda sensor complaint about the high CO2 value and thus the check engine was on.
 

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Alpenflitzer,

You may be correct that the two sensors are faulty but your reasoning is incorrect. The Lambda sensor measures oxygen and increases fuelling until O2 becomes unmeasurably low then it reduces fuelling.

Paul @ Kippen
 

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Discussion Starter #7
Yes Paul you are correct with the Lambda Sensors function.But this sensor was also out of service.
After I had replaced the CTS the check engine light came on from time to time again. Then i found, that the new CTS was faulty it had too weak signals. A new CTS has been put in and now everything is ok.
 

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Just to round this out....

As per my post earlier, car kept running with the CEL, and the tech II indicated an ignition fault. But nothing seemed to be wrong.

A couple of months ago, the car wouldn't start. After some checking, concluded that the fuel pump had died. So tank off, new pump and got a start. Confirmed that the pump had definitely stopped working.

But the car ran poorly, rough idle etc. Found that the rubber hose from the charcoal filter was split just where it connected to the fuel body. Quick temp fix with some tape, car ran fine. AND the CEL light went out and has never come back.

Moral: diagnostics, including Tech II can be as confused as we are.
 

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Discussion Starter #9
Late, but still in this year. Yes I once had similar problem with the rubber hose. Somehow confusing with the CEL isn´t?
 
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