P0418 — Secondary Air Injection System Switching Valve B Circuit Shorted
Can drive — fix at your convenience.
What P0418 means
This code means the engine computer detected a short circuit in the control wiring for the secondary air injection switching valve 'B'. A short usually means a wire is rubbing against metal or another wire, or the valve has an internal fault. The fix typically involves locating and repairing the shorted wiring or replacing the valve.
Common symptoms
- Check engine light is on
- No noticeable difference in driving
- Failed emissions or smog test
- Possible blown fuse related to the circuit
- Slightly elevated cold-start emissions
Common causes
- Wiring shorted to ground or to power
- Chafed or pinched wire in the valve harness
- Internal short within the switching valve
- Corroded or damaged electrical connector
- Faulty relay or control module driver
Typical repair cost
$120 – $450
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0418 code?
Yes, it's typically safe. The shorted circuit only involves an emissions valve, so your car drives and brakes normally. Just get it repaired before any emissions inspection.
How much does it cost to fix a P0418 code?
Most repairs run about $120 to $450. Tracing and fixing a shorted wire is usually cheaper, while replacing the switching valve costs more depending on the car.
Is a P0418 code serious?
No, it's low severity. It won't damage your engine or leave you stranded, but it keeps the check engine light on and can cause an emissions test failure.
What causes a short in this circuit?
Most often it's a wire whose insulation has worn through and is touching metal or another wire. A failed valve with an internal short or a damaged connector can also be the cause.