P0420 Catalyst efficiency below threshold (bank 1)
P0420 means that, based on the oxygen sensor signals, the engine control unit has rated the catalytic converter efficiency on bank 1 as too low. This does not always mean the converter is finished: an exhaust leak, the sensors, misfires and software have to be ruled out first. If deposits are the problem and the ceramic is intact, the converter can be restored.
Does restoration help?
Needs an in-person check
It can help if deposits have reduced the efficiency and the ceramic is intact. Cleaning does not fix thermal damage, melted ceramic or oil poisoning. The result is confirmed by measuring before and after - we do not promise in advance that the code will disappear.
A code shows where to look, but it is not a final diagnosis. We make the decision at the workshop after diagnostics and measurement.
Symptoms
- Check Engine light on - often the only sign.
- Reduced power or higher fuel consumption if the converter is clogged.
- Rattling in the exhaust - this usually means the inside of the converter has broken up.
Most common causes
- A worn converter or one clogged with deposits.
- An exhaust leak before the rear sensor.
- An ageing front oxygen sensor.
- Misfires, burning oil or coolant - these damage the converter.
- Engine management software - for some models the manufacturer has released an update.
Order of checks
What to do
- 1
Rule out other causes
We check for exhaust leaks, misfires and burning oil or coolant, and whether the manufacturer has released a software update.
- 2
Compare the sensor signals
At 1500-2000 rpm the front sensor signal fluctuates, while the rear one stays steady. If the rear sensor mirrors the front one, the converter no longer stores oxygen.
- 3
Decide on the converter
If the ceramic is intact and deposits are the problem - restoration, measured before and after. If it has broken up or melted - a replacement part or a new converter, and you can sell the old one to us.
FAQ
Questions about P0420
If the Check Engine light is on steadily and the car pulls as usual, P0420 is usually not an urgent fault. Still, do not put it off: a clogged converter can reduce power, and for cars registered from 2012 an active emission system fault means a grade 2 at the roadworthiness test. If the Check Engine light is flashing, drive as little as possible.
If deposits have reduced the efficiency, restoration can improve it, and the code may no longer appear. We do not guarantee this in advance: if the converter is thermally damaged or poisoned by oil, cleaning will not help. The result is confirmed by measuring before and after.
P0420
Not sure what is wrong with your car?
Tick the symptoms or enter the fault code - in 30 seconds you get a first assessment of whether the part can be restored. If restoring is no longer worth it, we buy the old converter.
Request
Book a check or a job
Leave your contact details - we will get back to you, clarify the situation and agree on a time.
- Phone+371 29 007 007
- Phone+371 28 777 998
- WhatsApp+371 20 099 444
- Emailinfo@autokatalizatori.lv
- AddressJūrkalnes iela 62, A7 bokss, Rīga
