Open circuit, damaged wiring or a poor connection in the valve control or supply wiring; Corroded, loose or water-contaminated connector at the switching valve; Switching valve solenoid with an open-circuit coil; Blown fuse or faulty relay supplying the valve circuit (layout depends on model); Chafed or heat-damaged harness near the exhaust or air pipework; Fault in the control unit output driver.

P0416

AIR System Switching Valve B Circuit Open.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
16: FaultThe specific fault in that area

What it means

P0416 means the engine control unit has detected an open circuit in the control circuit for secondary air injection switching valve B. This valve directs air from the secondary air system into the exhaust, usually only briefly after a cold start. The control unit saw no electrical continuity or current where it expected it when it checked the valve circuit. Which valve is 'B' (for example bank 2 or a second valve) depends on the vehicle.

Symptoms

Engine warning light on
Possible emissions test failure
Secondary air pump not heard running briefly after a cold start, or sounding different
Other secondary air system codes stored alongside it
Usually no change in drivability, though cold running may feel slightly rougher on some engines

Possible causes

Open circuit, damaged wiring or a poor connection in the valve control or supply wiringlikely
Corroded, loose or water-contaminated connector at the switching valvelikely
Switching valve solenoid with an open-circuit coillikely
Blown fuse or faulty relay supplying the valve circuit (layout depends on model)possible
Chafed or heat-damaged harness near the exhaust or air pipeworkpossible
Fault in the control unit output driverrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including engine temperature at the time it set
Check for other secondary air codes, which may point to a shared fuse, relay or wiring fault
Inspect the valve connector and nearby harness for corrosion, water, heat damage, chafing or pushed-out pins
Check the relevant fuse and relay against the wiring diagram for your model
With the connector unplugged, measure the valve solenoid resistance and compare it with the manufacturer's specification; an open or very high reading means the valve is faulty
Check for supply voltage and a control signal or ground at the connector when the system is commanded on, following the wiring diagram
Carry out a scan tool actuator test of the valve and listen or feel for it operating
Check for any technical bulletins or calibration updates for your model and engine

How to fix

Repair or replace damaged wiring and fix any open circuit found
Clean, repair or replace a corroded or damaged connector and make sure it is fully seated
Replace the switching valve if the solenoid is open circuit or does not operate
Replace a blown fuse or faulty relay, and find out why it failed
Update the control unit calibration only if the manufacturer lists an outdated calibration as a known cause for this code
Clear the code after repair and confirm it does not return on a cold start

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as this fault rarely affects safety or causes engine damage. Get it fixed in good time, as it may cause an emissions test failure and a persistent warning light could hide new faults.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.