Reductant Injection Air Pressure Sensor Circuit High
The P209D code indicates that the reductant injection air pressure sensor circuit is reading a higher voltage than expected. This sensor monitors the air pressure used to inject diesel exhaust fluid (DEF) into the exhaust stream. A high circuit condition can be caused by a faulty sensor, wiring issues, or a problem with the reductant injection system. This can lead to incorrect DEF dosing, potentially causing increased emissions and triggering the check engine light.
01. Most Common Causes
- Faulty reductant injection air pressure sensor
- Short to voltage in sensor wiring or connector
- Corroded or damaged sensor connector
- Failed reductant injection pump or control module
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or power
- Increased diesel exhaust fluid consumption
- Possible failed emissions test
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all codes and freeze frame data.
Step 2: Visually inspect the reductant injection air pressure sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor voltage reference and signal circuits using a multimeter; compare to manufacturer specifications.
Step 4: If wiring is intact, replace the reductant injection air pressure sensor and clear the code.
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 increased emissions and potential damage to the exhaust aftertreatment system. It is recommended to diagnose and repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the vehicle and shop rates. The sensor itself is relatively inexpensive.