P0420 code meaning
Secondary Air Injection System Relay "B" Circuit Malfunction
Powertrain systemGeneric code
What each part of P0420 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 20 | The exact fault in that area. |
What to do next
- Note the code and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the part the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0420
What does P0420 mean?
P0420: Secondary Air Injection System Relay "B" Circuit Malfunction. It is a Powertrain code, with the same meaning on every make.
Is it safe to drive with P0420?
If the check engine light is steady, you can usually drive to a mechanic soon. If it flashes, or the car runs badly, stop driving and have it checked: the fault can cause more damage.
How do I fix P0420?
The code tells you where the fault was found, not which part failed. A mechanic checks the wiring, connectors and sensors in that circuit before replacing parts. Look for a recall or service bulletin for your car too.