P0412
Fix within 1-2 weeksSecondary Air Injection System Switching Valve "A" Circuit Malfunction. This means the engine computer detected an electrical problem with the valve that controls airflow in your vehicle's secondary air injection system. This system helps reduce emissions during cold starts.
Code P0412 means your secondary air injection switching valve "A" has an electrical fault. Common causes: Faulty valve (60%), wiring issues (25%), relay failure (10%). Drivability: Yes, safe to drive. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0412?
Yes, safe to drive
No restrictions on driving, but address the issue for emissions compliance.
Stop driving immediately if: Flashing CEL (indicates a more severe misfire, not typically associated with P0412 alone), significant power loss (not typical for P0412).
Symptoms of P0412
- 1Check Engine Light is on
- 2No noticeable drivability issues
- 3Vehicle will fail an emissions test
Common Causes of P0412
Parts most likely causing this code, ranked by probability
The valve itself has an internal electrical fault, preventing it from opening or closing correctly.
60% of P0412 cases are fixed by replacing this part
Damaged wires, corroded connectors, or a loose connection to the AIR switching valve can interrupt the electrical circuit.
25% of P0412 cases are fixed by repairing wiring or connectors
A faulty relay can prevent power from reaching the switching valve, causing a circuit malfunction code.
10% of P0412 cases are fixed by replacing the AIR pump relay
A rare internal fault within the PCM can incorrectly report a circuit malfunction for the AIR switching valve.
5% of P0412 cases are fixed by replacing or reprogramming the PCM
Check These First (Before Buying Parts)
- Check the fuse for the secondary air injection system in your vehicle's fuse box.
- Visually inspect the wiring harness leading to the secondary air injection switching valve "A" for any obvious cuts, fraying, or signs of rodent damage.
- Check the electrical connector at the valve for corrosion or looseness.
How to Diagnose P0412
- 1Check the fuse for the secondary air injection system.
- 2Visually inspect the wiring harness and electrical connector for the AIR switching valve "A" for damage, corrosion, or looseness.
- 3Use a multimeter to test for proper voltage at the AIR switching valve connector when commanded on by a scan tool.
- 4Test the resistance of the AIR switching valve "A" solenoid.
- 5Test the secondary air injection pump relay for proper operation.
- 6If all other components test good, consider a PCM diagnosis.
P0412 on Popular Vehicles
Honda Accord
2003-2012Honda Accords, especially those with V6 engines, are known to have issues with the secondary air injection system, including the switching valves. Corrosion in the connectors or an internal electrical failure of the valve are common.
70% fixed by replacing the AIR switching valve or repairing wiring
Ford F-150
2004-2014Ford F-150s with the 5.4L engine sometimes experience P0412 due to a failed AIR switching valve or a corroded electrical connector. The location of these components can expose them to road grime and moisture.
65% fixed by replacing the AIR switching valve or repairing wiring
Chevrolet Silverado
2007-2013Chevrolet Silverados, particularly those with the 5.3L and 6.0L engines, can trigger P0412. The AIR pump and its associated valves are exposed, making them susceptible to moisture and debris, leading to electrical faults in the switching valve.
70% fixed by replacing the AIR switching valve or repairing wiring
Frequently Asked Questions
What does P0412 mean?
P0412 indicates an electrical circuit malfunction in the secondary air injection system's switching valve "A". This valve controls the airflow that helps warm up your catalytic converter during cold starts to reduce emissions.
Can I drive with P0412?
Yes, you can drive safely with P0412. This code does not typically affect engine performance or drivability. However, your vehicle will produce higher emissions during cold starts and will fail an emissions test.
Will P0412 clear itself?
No, P0412 will not clear itself. The Check Engine Light will remain on until the underlying electrical fault with the secondary air injection switching valve "A" circuit is diagnosed and repaired.
How do I fix P0412 myself?
Start by checking the fuse for the secondary air injection system. Then, inspect the wiring and connector to the AIR switching valve "A" for damage. If those are good, you'll need a multimeter to test the resistance of the valve and check for proper voltage at its connector. If the valve or its relay tests bad, replace it.
How much does it cost to fix P0412?
DIY repair costs for P0412 are typically $50-$200, mainly for a new AIR switching valve or relay. Professional repair costs range from $150-$500, including parts and labor.
P0412 keeps coming back - why?
If P0412 keeps returning, it often means the initial diagnosis missed the root cause. Double-check for intermittent wiring issues, a faulty relay, or a problem with the AIR pump itself that might be overloading the circuit. A rare possibility is a PCM issue.
Will P0412 fail emissions/smog test?
Yes, P0412 will cause your vehicle to fail an emissions or smog test. The secondary air injection system is a critical component for reducing cold-start emissions, and a fault in its circuit will trigger a "not ready" status or an outright failure.
What's the difference between P0412 and P0410?
P0412 specifically indicates an electrical circuit malfunction with the secondary air injection switching valve "A". P0410 is a broader code indicating a general malfunction in the secondary air injection system, meaning the system isn't performing as expected, but doesn't pinpoint a specific electrical circuit fault.
P0412 on Honda Accord?
P0412 on a Honda Accord often points to a faulty secondary air injection switching valve or a problem with its associated wiring. These valves can fail electrically over time. Always check the fuse and wiring first before replacing the valve.
Questions to Ask Your Mechanic
Did you test the resistance of the secondary air injection switching valve "A" solenoid?
Good answer: Yes, I measured the resistance and it was outside the manufacturer's specification, indicating an internal fault in the valve.
Did you check for voltage at the switching valve connector when the system was commanded on?
Good answer: Yes, I confirmed there was proper voltage reaching the connector, which tells me the wiring and relay up to that point are good.
Repair Cost Estimate
DIY Repair
Parts only
$50-$200
Shop Repair
Parts + labor
$150-$500
Save $100-$300 by doing it yourself
Difficulty
intermediate
Time
1-3 hours
Intermediate - requires basic hand tools, a multimeter for electrical testing, and ideally a scan tool to command the system on and clear the code.
Cost of Waiting
Ignoring P0412 means your vehicle will continue to produce higher emissions during cold starts and will fail any required emissions tests. While it won't cause immediate engine damage, the catalytic converter will take longer to reach operating temperature, potentially shortening its lifespan over many years.
While You're In There...
If the switching valve is being replaced, it's a good time to inspect the AIR pump for proper operation, especially if it's easily accessible in the same area. A failing pump can sometimes stress the valve circuit.
The relay is an inexpensive electrical component that can also cause circuit issues. Replacing it along with the valve ensures the entire circuit is fresh.
Tools You'll Need
- OBD-II scan tool
- Multimeter
- Basic hand tools (sockets, wrenches)
- Wire strippers/crimpers (if repairing wiring)
P0412 is a common emissions code. It doesn't mean your engine is in immediate danger, and the repair is usually a straightforward electrical fix, often involving replacing a single component.
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Your Next Steps
Step 1: Check the fuse for the secondary air injection system. If blown, replace it and see if the code returns.
Step 2: Visually inspect the wiring harness and connector to the secondary air injection switching valve "A". Look for any damage, corrosion, or loose connections. Repair as needed.
Step 3: If the fuse and wiring are good, use a multimeter to test the resistance of the switching valve solenoid and check for proper voltage at the connector when the system is commanded on (requires a scan tool). Parts you'll likely need: Secondary Air Injection Switching Valve "A" or an AIR Pump Relay.