P209B - Reductant Injection Air Pressure Sensor Circuit Range/Performance
The P209B code indicates that the reductant injection air pressure sensor circuit is reporting a signal that is out of the expected range or performance parameters. This sensor monitors the air pressure used to inject diesel exhaust fluid (DEF) into the exhaust stream. A fault can lead to improper DEF injection, affecting emissions control and potentially triggering the check engine light.
01. Most Common Causes
- Faulty reductant injection air pressure sensor
- Wiring or connector issues in the sensor circuit
- Blocked or leaking air line to the sensor
- Faulty reductant injection pump or control module
02. Symptoms You Will Notice
- Check engine light illuminated
- Reduced engine performance or power
- Increased emissions or failed emissions test
- Possible DEF system warning messages
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for related codes.
Step 2: Visually inspect the sensor, wiring, and air lines for damage, corrosion, or blockages.
Step 3: Test the sensor's voltage and resistance with a multimeter and compare to manufacturer specs.
Step 4: Check the reductant injection pump and control module for proper operation.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive short distances, but prolonged driving may cause reduced performance and increased emissions. It's best to diagnose and repair promptly to avoid potential damage to the DEF system.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts and labor. The sensor itself costs $50-$150, and labor adds $100-$250 depending on the shop.