OBD-II trouble code
P0416: Secondary Air Injection System Switching Valve B Circuit Open
The control circuit for secondary air switching valve "B" is open — the computer commands the valve but sees no electrical load at all.
Quick facts
- System
- Powertrain
- Category
- Emissions / Secondary Air
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $60 – $450
- DIY difficulty
- Advanced DIY
What does P0416 mean?
P0416 narrows the valve "B" fault down specifically to an open circuit: when the computer energizes the valve's solenoid it expects to see current flow, and it sees none. Somewhere between the PCM driver, the wiring, the connector, and the solenoid winding, the path is broken.
The usual suspects, in order of likelihood: a corroded or backed-out connector terminal (moisture is endemic in secondary air systems), a broken wire — often where the harness flexes or runs near exhaust heat — a blown solenoid winding inside the valve, or a blown fuse if the circuit is fed through one. It's the same diagnosis as any open-circuit code: verify power and ground at the valve while commanded, and measure the solenoid's resistance; an infinite reading condemns the valve, a good reading sends you back into the harness.
Drivability impact is minimal, but the cold-start emissions function is lost and the code will fail inspection.
Common causes
- Broken wire in the valve control circuit
- Corroded, backed-out, or spread connector terminal
- Open solenoid winding inside the switching valve
- Blown fuse feeding the valve circuit
- Heat-damaged harness section near the exhaust
- PCM driver failure (rare)
Symptoms
- Check engine light on
- Failed emissions test
- Possibly slightly longer/rougher cold-start warm-up
- No other noticeable drivability symptoms in most cases
Diagnostic steps
- 1.Check the AIR system fuse first — it's the 30-second test.
- 2.Measure the valve B solenoid resistance at its connector; an open (infinite) reading means the valve.
- 3.If the solenoid reads good, back-probe for power and ground while commanding the valve with a scan tool.
- 4.Inspect the connector terminals for corrosion and tension; repair terminals rather than just re-seating.
- 5.Trace the harness for breaks, especially at flex points and near exhaust components.
- 6.Repair and re-run a cold-start cycle to confirm the code stays clear.
Repair cost
$60 – $450
If it's a fuse, terminal, or wire, this is a cheap fix. A replacement switching valve typically runs $50-$200 plus modest labor. Diagnose before replacing — open circuits are more often wiring than valve.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with secondary air injection pump replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.