Anyone know about fault codes?

[RB Will]

Hi all. I have a 2005 Subaru Legacy Spec B that has been behaving strangely lately.

I got an engine light and cruise control light flashing the other day. Cruise stopped working but nothing else was wrong. Exactly 48hours later the lights went out cruise is now working but the car kept stalling when coming to a stop.

I have had a friend plug a diagnostic unit into it and it came up with

PO420 - Catalyst System Efficiency Below Threshold Bank 1.

We don't know what this means of if this related to the lights as there is no date to it and since we cleared it we have not been able to make the car throw out any other faults and it seems to be driving perfectly at the moment too. Weird.

Does anyone know if the MAF is a common fault on the 3.0 engine? I know it is on my P1 but don't know if it is a common Subaru thing. Also does the 3.0 have an idle control valve or is it incorporated into the throttle body, maybe that was sticking.

Thanks for any help.

Will

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That usually means one of the lambdas are playing up.

[RB Will]

That was another thought. Its just odd that the car is driving fine otherwise. Its not running rich and is pulling as strong as ever when driving normally. It just didn't like coming to a halt.

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Dirty fuel can cause the code to be thrown up as the lambda can pick that up.

[RB Will]

That could make sense as since we cleared the fault code and I have put a fresh tank of fuel in it has been running perfectly.