The switching valve opens the path between the secondary air pump and the exhaust only when the engine computer wants air to flow. A P0415 code means the computer found a problem in the circuit for switching valve B.
This guide explains how the switching valve works, what breaks its circuit and how to test it step by step.
P0415 Code Breakdown
Every OBD-II code follows the same five-character pattern set by the SAE J2012 standard. Each character narrows down which system has the fault. This table shows what each part of the code tells you.
| Character | Meaning | What It Tells You |
|---|---|---|
| P | Powertrain | The fault is in the engine or transmission systems. |
| 0 | Generic (SAE) code | The definition is the same on every OBD-II vehicle. |
| 4 | Auxiliary emission controls | The fault involves emission control systems such as EGR, secondary air, EVAP or the catalytic converter. |
| 15 | Specific fault | Secondary Air Injection System Switching Valve B Circuit Malfunction |
What the P0415 Code Means
The SAE J2012 standard defines the P0415 code as Secondary Air Injection System Switching Valve B Circuit Malfunction. The secondary air injection (AIR) system pumps fresh air into the exhaust for the first 30 seconds to 2 minutes after a cold start. The extra oxygen burns leftover fuel in the exhaust, which heats the catalytic converter quickly and cuts emissions while the engine is cold.
A typical system has an electric air pump, a relay that powers it, one or more switching or check valves that open the air path and stop exhaust from flowing back, and hoses or pipes to the exhaust ports. The powertrain control module (PCM) runs the pump and opens the valves, often using a vacuum solenoid or an electric valve.
The PCM checks the system by watching the upstream oxygen sensors. When the pump runs, the sensors should read lean because of the extra air. On some vehicles, a pressure sensor in the air path does the same job.
Switching valve B is a second valve, often for bank 2 on V engines. On many vehicles, the PCM controls it through a vacuum solenoid that opens a vacuum-operated valve. On others, the valve is electric. This general code covers any circuit fault the PCM sees.
Symptoms of a Bad Switching Valve B
Most symptoms appear right after a cold start. Common signs of a P0415 code include:
- Check engine light on
- Secondary air system not working
- Other secondary air codes set at the same time
- Failed emissions test
- Reduced power after a cold start on some vehicles
The engine usually runs normally once warm, since the system only works after a cold start.
Most Common Causes of the P0415 Code
These are the usual causes:
- Damaged wiring or connector. Heat and moisture near the exhaust attack it.
- Failed solenoid or valve coil. The coil opens or shorts.
- Blown fuse or lost power feed.
- Corroded connector. Water gets in through a worn seal.
- PCM driver fault. Rare.
Tools You Will Need
You can do most of this testing at home with basic tools:
- OBD-II scan tool that can command the air pump and valves
- Digital multimeter and test light
- Hand vacuum pump for vacuum-operated valves
- Wiring diagram for your vehicle
- Flashlight for checking hoses and valves
Step-By-Step Diagnosis of the P0415 Code
Many secondary air tests need a cold engine, since the system only runs for a short time after a cold start. Let the vehicle sit for several hours before testing.
Find the Valve and Solenoid
Use the service manual to find switching valve B and the solenoid that controls it. Check the connector for corrosion, broken locks and water, and the wiring for heat damage.
Check Power and Ground
Unplug the solenoid or valve and turn the key on. Check for battery voltage on the feed wire with a test light. Command the valve with a scan tool and check that the PCM grounds the control wire, if your vehicle is wired that way.
Measure Coil Resistance
Measure across the solenoid or valve terminals and compare it with the specification, often in the range of about 20 to 40 ohms for vacuum solenoids. An open or very low reading confirms a bad coil.
Check the Wiring
With the battery disconnected and the PCM unplugged, check the control wire for continuity end to end and for shorts to ground and power.
On vacuum systems, also check that vacuum reaches the valve when the solenoid is on, since a cracked hose stops the valve even with a good circuit.
How to Fix the P0415 Code
Match the repair to what your tests found. Then clear the code and drive under the same conditions that set it.
- Repair the connector or wiring.
- Replace the solenoid or valve if its resistance is out of range.
- Replace a blown fuse after finding the cause.
- Seal the connector to keep water out.
After the repair, clear the codes and let the vehicle sit until the engine is fully cold. The PCM tests the system on the next cold start.
Common Mistakes to Avoid
These mistakes waste money or leave the real fault in place:
- Replacing the pump when the circuit code points to the valve
- Testing only on a warm engine
- Ignoring a shorted coil that may have damaged the PCM driver
What Repairs Cost
The cost to fix a P0415 code depends on the cause. This table shows typical ranges for parts and labor.
| Repair | DIY Cost | Typical Shop Cost |
|---|---|---|
| Air pump relay or fuse | $5 to $40 | $50 to $150 |
| Switching or check valve | $40 to $250 | $150 to $500 |
| Air injection pump | $100 to $500 | $300 to $1,000 |
| Hose or vacuum line | $5 to $40 | $50 to $150 |
| Wiring or connector repair | $10 to $40 | $100 to $300 |
Valve and solenoid repairs are moderate in cost. On some V engines, the valves sit at the back of the engine or under the intake, which adds labor.
Is It Safe to Drive with a P0415 Code?
Yes, in most cases. The secondary air system only works for a short time after a cold start, so a fault does not usually affect how the engine runs once it is warm.
The vehicle will likely fail an emissions test, and some engines enter a reduced power mode if the pump or valves fail. If you hear a loud whine or see smoke from the pump, have it checked soon.
Related Codes
These codes often show up with this one or point to the same system:
| Code | Meaning |
|---|---|
| P0410 | Secondary Air Injection System Malfunction |
| P0411 | Secondary Air Injection System Incorrect Flow Detected |
| P0412 | Secondary Air Injection System Switching Valve A Circuit Malfunction |
| P0418 | Secondary Air Injection System Relay A Circuit Malfunction |
| P2440 | Secondary Air Injection System Switching Valve Stuck Open Bank 1 |
Fixing Switching Valve B
A P0415 code means the PCM found a fault on secondary air switching valve B. Wiring, connectors and failed coils cause most cases.
- Find the valve and solenoid.
- Check power and ground.
- Measure coil resistance.
- Check the wiring and vacuum supply.
Frequently Asked Questions
Does the P0415 Code Mean the Air Pump Is Bad?
No. This code points to the switching valve circuit, not the pump. The pump may be fine. Test the valve’s wiring, connector and coil first.
What Is a Switching Valve?
It is the valve that opens the air path from the pump to the exhaust only when needed. On many vehicles it combines with a check valve that stops exhaust from flowing back into the pump.
How Long Does the Air Pump Run?
On most vehicles, it runs for about 30 seconds to 2 minutes after a cold start, then shuts off. You may hear a whirring or humming sound from the engine bay during that time. It does not run on a warm engine.
Why Do Air Pumps Fail?
Moisture is the main enemy. Water from condensation or road spray can get into the pump through its inlet or a leaking check valve, which rusts the motor and bearings. A check valve that lets exhaust back into the pump can also melt it.
Which Vehicles Use Secondary Air Injection?
Many vehicles from the late 1990s through the 2010s use it, including models from Toyota, Lexus, Volkswagen, Audi, BMW, Mercedes-Benz, GM and Porsche. Newer engines often meet cold start emissions rules with other methods, such as retarded timing and faster-heating converters.
Can I Remove the Secondary Air System?
Not legally for road use in most places. It is part of the emissions system, and removing it will set codes and fail an inspection. Repair the faulty part instead.