OBD-II code · Powertrain (generic)
P0418 Secondary Air Injection System Relay "A" Circuit Malfunction
General electrical fault in the secondary air injection pump relay A circuit. Without the relay, the air pump cannot be commanded and the system cannot complete its cold-start function.
Is it safe to drive with P0418?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyAir pump relay failed
- PossibleWiring or connector fault
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Secondary Air Relay, Secondary Air Pump, Relay Wiring
Related codes
- P0415Secondary Air Injection System Switching Valve B Circuit
- P0416Secondary Air Injection System Switching Valve B Circuit Open
- P0417Secondary Air Injection System Switching Valve B Circuit Shorted
- P0419Secondary Air Injection System Control B Circuit
- P041AEGR Temperature Sensor B Circuit
- P041BEGR Temperature Sensor B Circuit Range/Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.