P2439: Secondary Air Injection System Flow/Pressure Sensor Circuit Intermittent/Erratic Bank 2
The P2439 code indicates an intermittent or erratic signal from the secondary air injection (AIR) system pressure sensor on Bank 2. The AIR system pumps fresh air into the exhaust to reduce emissions during cold starts. The pressure sensor monitors airflow; when the signal fluctuates or drops out, the PCM sets this code. Common causes include a faulty pressure sensor, wiring issues, or a failing AIR pump or check valve.
01. Most Common Causes
- Faulty secondary air injection pressure sensor
- Damaged or corroded wiring/connectors to the sensor
- Failed secondary air injection pump or relay
- Stuck or leaking check valve
02. Symptoms You Will Notice
- Check Engine Light on
- Failed emissions test
- Possible rough idle or hesitation on cold start
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the AIR system components and wiring for damage.
Step 3: Test the pressure sensor signal with a multimeter or scan tool while cycling the AIR pump.
Step 4: Check the AIR pump operation and check valve function.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, but the vehicle may fail emissions and the check engine light will stay on. It's best to repair soon to avoid further issues.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and sensor replacement, but could be higher if the pump or valves need replacement.