Faulty switching valve B solenoid or its internal electrical circuit; Damaged, chafed or corroded wiring to the valve; Poor connection at the valve or control unit connector (corrosion, loose terminal, water ingress); Blown fuse or faulty relay supplying the secondary air circuit; Moisture or contamination damaging the valve or pump assembly; Faulty control unit output driver for the valve.

P0415

AIR System Switching Valve B Circuit.

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
15: FaultThe specific fault in that area

What it means

P0415 means the engine control unit has detected an electrical fault in the circuit of switching valve B in the secondary air injection system. This valve directs air from the pump into the exhaust during cold start to help the catalyst warm up quickly. The control unit sets the code when the voltage or current it sees on the valve's control circuit does not match what it commanded. Which valve counts as B depends on the model and engine layout.

Symptoms

Engine warning light on
Little or no other change in driveability
Possible failure of an emissions test
Secondary air pump may run noisily or not at all at cold start
Slightly higher cold-start emissions or an exhaust smell
Other secondary air codes stored alongside it

Possible causes

Faulty switching valve B solenoid or its internal electrical circuitlikely
Damaged, chafed or corroded wiring to the valvelikely
Poor connection at the valve or control unit connector (corrosion, loose terminal, water ingress)likely
Blown fuse or faulty relay supplying the secondary air circuitpossible
Moisture or contamination damaging the valve or pump assemblypossible
Faulty control unit output driver for the valverare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting any other secondary air codes and the conditions when the fault set (usually a cold start).
Visually inspect the switching valve B, its connector and wiring for damage, chafing, heat damage, corrosion or water ingress.
Check the fuse and relay for the secondary air system against the wiring diagram for that model.
Using the wiring diagram, check for supply voltage and a good earth or control signal at the valve connector with ignition on or during a commanded test.
Measure the valve solenoid resistance and compare it with the manufacturer's specification.
Where the scan tool allows, command the valve on and off and listen or feel for it operating, and check the control circuit response.
Test the wiring between the valve and control unit for open circuit, short to earth and short to voltage.
If the valve is vacuum operated on your model, check the vacuum supply and the vacuum solenoid that controls it.

How to fix

Repair or replace damaged wiring and clean or replace corroded connector terminals.
Replace the switching valve B if its solenoid resistance or operation is out of specification.
Replace any blown fuse or faulty relay once the cause of the failure has been found.
Dry out and repair any water ingress, and replace the valve or pump assembly if it has been contaminated.
Only after all wiring and the valve are proven good, repair or replace the control unit if its output driver is faulty.

Can I keep driving?

Low severity

The car can normally be driven as the fault affects only the cold-start emissions system. Book it in for repair soon, as the warning light will stay on and an emissions test may fail.

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