Alfa 147 Lambda fault

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Alfa 147 Lambda fault

Postby mattys147 » Tue Oct 11, 2011 8:56 pm

Hello, I hope you can help me as i am at my witts end with this fault. Basically my car has three lamba sensors two at the precat and one at the cat It is an alfa 147 1.6 tspark. Bank1 s1 and bank 2 s1 are flucuating from rich to lean normally, However bank 1 s2 is sitting at a steady 0.45 volts. I have swapped known good sensors over but it always reads the same 0.45 volts regardless of rpm etc. I have even changed the engine wiring loom for a known good one but it’s still presently the same, it will log a fault every couple of days saying that bank1 s2 out of range. I am now thinking it could be a problem with my precat and the sensor and wiring is ok, however is this possible? As the other sensor in the precat is working well. Any help or ideas great fully appreciated..
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Re: Alfa 147 Lambda fault

Postby Alan » Wed Oct 12, 2011 7:24 am

Hi,

I am not sure what type of sensor the post cat one is, but what you describe may well be normal.

Pre cat sensors will typically be switching rich / lean but you expect the post cat sensor to be sitting at a fairly steady level unless there is a problem with the catalytic converter. If you blip the throttle then you should see the post cat sensor jump a bit (on a scope, but perhaps not on a meter).

Scan tool codes do need to be treated with care as what they mean can vary a bit - the out of range code you are getting can mean a couple of different things. It may be that the ECU is picking up a signal that is out of the allowed range for the sensor (perhaps 0V or 12V if there is a wiring fault somewhere) or it may mean that the sensor is working OK, but the catalytic converter is on its way out and under load the post cat sensor is switching rather than giving a steady signal.

Perhaps someone here with better knowledge of the Alfa ECU can clarify a bit further?

Alan
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Re: Alfa 147 Lambda fault

Postby mattys147 » Wed Oct 12, 2011 10:00 am

Thanks for your reply, It is the sensor before the cat bank 1 s2 that is causing the problems. I have changed the engine loom over to rule out wiring etc. Really at a loss.
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Re: Alfa 147 Lambda fault

Postby Alan » Wed Oct 12, 2011 12:30 pm

Hi,

Normally Bank 1 S1 would be pre cat and Bank 1 S2 would be post cat. Are you sure which sensor is reporting a problem?

Alan
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