Car sets PO420 code. Started only on interstate at 70mph. Now sets at lower speeds. Freeze frame does not store O2 readings. Fuel trims (long and short) are both even and slightly above positive. Car uses no oil,runs fine,recent tune up. Suspect O2 sensors, rear O2 reads efficiency, but if front O2 was slow, could that set code? When car is driven with SOLUS, O2 reading are normal. SOLUS has tech tip to clean or replace MAF sensor,MAF was cleaned but not replaced. I have two Celicas with this problem at this time. Thanks for any help.
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What is the mileage on this vehicle? Cats are warrantied 8 years/80,000 miles.
If the fuel trims are in spec and no exhaust leaks anywhere before the rear O2 I would say its the Cat. There are no TSB's for this as far as reflashing the PCM for this code and if I remember right B1S1 is an oxygen sensor not a A/F sensor, so you could look at your freeze frame, duplicate the conditions and graph both front and rear O2's to confirm Cat fault.
SteveLast edited by Steve6911; 03-10-2010, 03:01 PM.
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