I recently read in Honest Johns letters page in the Saturday Telegraph under the header "Cat fued". His reply suggesting obtaining a non original CAT for a Merc. to avoid the excessive cost of an O.E.M. part.
I've had to have a replacment CAT fitted to my Saab 9-3, I was quoted more than £1000 so I've had a non Saab one fitted at less than half the cost the justification being that the car although in excellent condition has done 100,000 miles.
But the engine management warning light still comes on.
Should Saab be able to reset this light to function normally and if so how much are they likely to charge?
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A pound to a penny says the lambda sensor is not working correctly. Why was the cat replaced?
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Nick,
Thanks for the reply, I've heard of the Lambda sensor but I don't know what it does.
The car just conked out while being driven, it was towed to a Saab garage who said the direct ignition had failed and warned this could have allowed unburned fuel into the exhaust and damaged the CAT
They fixed the ignition and were right about the CAT - now its a dead CAT.
Paulm
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ive known of a case where the cat went on a vectra with the same symptoms as yourself ie after fitting the copy cat the mil light came on
it was assumed it was a faulty cat and the suppliers sent another this one did the same,a new oe one was fitted and the light stayed out after obviously being reset .ive never been a fan of copy parts cats and always fit s/h low mileage bumped cars replacements they are better quality (oe) and you know the job is done,did you not consider s/h from a trusted saab breaker?
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Hi oldman, I hadn't considered S/H as it was an opportunity to give my local garage the business, I will now be happy to take the car back to them for it's next MOT!!
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Doubt your SAAB will have dual lambda sensors - so unlikely that MIL light is anything to do with the cat. The lambda sensor signal needs checking first.
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the light would not come on if the cat was an empty box ,as mine is ,as i removed the guts =more power. must be lamda or other sensor fault .you should be able to tell from diagnosic socket if fault code is still stored.
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paulm
The lambda sensor sits in the exhaust in front of the cat. It continually monitors the excess oxygen level in the exhaust and sends a signal to the engine fuelling to maintain the correct mixture so the cat works properly. The cat gets the correct level of oxygen and can work properly. Note, this control all happens upstream of the cat. So, as has been pointed out, even if the cat isn't there if the lambda sensor is working corectly then the engine management light won't come on. So, an after market cat can't cause the problem described. The chances are there's another problem somewhere.
The only caveat is that some cars, and Saab may be one, have OBD (on board diagnostics) which actually monitor the emmisions after the cat. Your garage needs to be sure exactly what they are dealing with. The chances are that the problem is more likely to be the lambda sensor rather than the cat.
JS
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John S and Axleman,
Interesting news, 24hrs and 250 miles after the new (non original) cat was fitted the warning light has stoped coming on.
Why? there is no other problem with the engine. I think you are both on the right track, it took at least a day before the light came on after the original cat was affected by the fuel, now it's taken the same before the light has stoped coming on after the new (non Saab)cat was fitted. I don't know but maybe the sensor system (either side of the cat ) took this time to respond while any residual contaminents or conditions cleared from the exhaust system.
Saab said it should be possible to reset the warning sytem even with the non original cat using Tech 2 diagnostic equipment.
Fingers crossed this may not be nessesary.
Going back to HJ's suggestion to try a non original cat perhaps this experience may be of help to anyone horrified at the cost of having such equipment fitted by official dealers.
Paulm
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