P2431Secondary Air Injection

Secondary Air Injection System Air Flow/Pressure Sensor Circuit Range/Performance (Bank 1)

The control module has detected that the secondary air injection air flow or pressure sensor on bank 1 is reporting a value that does not match expected performance. The secondary air system pumps air into the exhaust after cold start to help the catalyst heat up faster.

🚗 Yes, in most cases. It is an emissions fault that mainly affects cold-start emissions. Repair it to pass emissions testing.
MEDIUM
severity
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🎯 Top Causes, Ranked by Likelihood

#1Faulty air flow/pressure sensor$80-$250
35%
The sensor reports inaccurate flow or pressure values.
#2Failing secondary air pump$200-$500
25%
A weak pump produces flow outside the expected range.
#3Clogged air injection passages$100-$400
25%
Carbon buildup restricts flow into the exhaust, skewing the reading.
#4Wiring or connector fault$40-$200
15%
High resistance or a bad connection distorts the sensor signal.

🩺 Common Symptoms

💰 Repair Cost: DIY vs Shop

DIY Cost
$80-$400
Shop Cost
$200-$600

📋 Free OBD2 Code Cheat Sheet

The 50 most common codes with likely cause and DIY fix cost. Sent once, no spam.

🔧 How to Diagnose P2431

1Inspect the secondary air sensor connector and wiring for faults.
2Command the secondary air pump on and observe flow and pressure data.
3Check air injection passages and hoses for carbon blockage.
4Replace the sensor or pump as indicated, then clear and retest.

❓ Frequently Asked Questions

What is secondary air injection?
It pumps fresh air into the exhaust after a cold start so the catalyst heats up faster and reduces emissions.
Is it safe to drive?
Yes, in most cases. It mainly affects cold-start emissions, not general drivability.
Could carbon buildup cause this?
Yes. Clogged air passages are a common cause of range and performance faults in this system.

🔗 Related Codes

P2432P2440P2441P0410P0491
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