Can you keep driving?
Can you keep driving?
Stop driving if any of these apply
- !The engine starts running much worse, stalls, or the warning light flashes.
- !The vehicle begins to overheat, knock, or lose power sharply while the code is active.
What to check first
Step-by-step checks
- 1
Free - no tools
Let the exhaust cool before checking the valve and plumbing
- 2
Free - no tools
Inspect the switch valve, connector, and harness for heat damage or moisture
- 3
Basic tool needed
Check whether the code appeared after wet weather, cold starts, or recent exhaust work
- 4
Basic tool needed
If the valve is vacuum-controlled, inspect the solenoid and hose routing too
- 5
Basic tool needed
If scan data is available, compare commanded operation with actual response
If the code returns
- -If the valve sticks or does not move, the valve itself moves higher on the list.
- -If the harness movement changes the fault, wiring repair should come first.
- -If the code returns after replacement, recheck the command and supply side again.
Background
What this code means
P0416 is a generic OBD-II code for a secondary air injection switch valve B malfunction.
The ECU is seeing the valve behave in a way it does not trust, so flow into the exhaust is not happening the way it should during the cold-start strategy.
Diagnosis
Common causes
Failed switch valve
The valve may be sticking or not moving correctly.
Vacuum supply or solenoid issue
The valve may not be getting the correct command or pressure.
Connector or wiring fault
A poor connection can make the valve look bad.
Moisture intrusion
Water can corrode the valve or connector and affect operation.
Avoid these mistakes
What not to do
- xDo not replace the sensor or valve first if there is obvious wiring, connector, or vacuum damage.
- xDo not ignore drivability changes just because the code sounds like an emissions fault.
Parts
Parts that may need replacing
See also
Related OBD codes
P0410
P0410 usually means the secondary air injection system is not working properly.
P0411
P0411 usually means the secondary air injection flow is incorrect.
P0412
P0412 usually means the secondary air injection control circuit has a malfunction.
P0413
P0413 usually means the secondary air injection valve circuit is malfunctioning.
P0414
P0414 usually means the secondary air injection switch valve A is shorted or malfunctioning.
P0415
P0415 usually means the secondary air injection switch valve B has a circuit malfunction.
Source notes
Generic OBD-II (SAE J1979 / ISO 15031-5). P0416 was expanded around common secondary-air switch-valve malfunctions, including vacuum issues, wiring damage, and moisture-related problems.
This guide is written as a generic multi-make reference, so bulletin history, sensor locations, and repair order can still change by manufacturer and engine family.
This is generic OBD-II guidance and should not override vehicle-specific service information. Exact diagnosis and repair steps vary by make, engine family, and model year.
Last reviewed: 2026-04-10
Reference: Open reference