What does code P0420 mean on a Land Rover and is it safe to drive?
P0420: Catalyst System Efficiency Below Threshold (Bank 1). Here's what it means on your Land Rover, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
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What this code means
The downstream oxygen sensor detects that the catalytic converter is not storing or converting exhaust properly. This is one of the most common check engine codes.
Common causes for your Land Rover
- Failed or aging catalytic converter
- Faulty downstream oxygen sensor
- Exhaust leak before or after the catalyst
- Engine misfire or rich/lean condition damaging the catalyst
Symptoms
- Check Engine Light on
- Often no drivability issues
- Possible failed emissions test
- Rotten egg smell in some cases
Typical fixes
- Replace catalytic converter
- Replace oxygen sensor(s)
- Repair exhaust leaks
- Fix underlying fuel/ignition issues first
Repair cost range
For a Land Rover, repairs for P0420 often fall between $400 and $2400, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Land Rover
Land Rover's 3.0L V6 supercharged engines trigger P0420 at high mileage. Always verify with OBD2 mode $06 catalyst efficiency data before replacing the converter given high repair costs.
Most commonly affected models
Range Rover 2010–2018Discovery Sport 2017+