Reductant Injection Air Pressure Sensor Circuit Low
The P2039 code indicates that the reductant injection air pressure sensor circuit is reading a voltage lower than the expected range. This sensor monitors the air pressure supplied to the diesel exhaust fluid (DEF) injector. A low circuit condition can be caused by a faulty sensor, wiring issues, or a problem with the reductant injection system. This can lead to improper DEF injection, affecting emissions control and potentially triggering the check engine light.
1. Most Common Causes
- Faulty reductant injection air pressure sensor
- Open or shorted wiring in the sensor circuit
- Poor electrical connection at the sensor connector
- Failed reductant injection pump or module
2. Symptoms You Will Notice
- Check engine light illuminated
- Reduced engine performance or power
- Increased emissions or failed emissions test
- Possible DEF system warning message on dashboard
3. 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 and wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's voltage and ground supply with a multimeter; compare to manufacturer specs.
Step 4: If wiring is intact, replace the reductant injection air pressure sensor.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive short distances, but the vehicle may fail emissions tests and the check engine light will remain on. Prolonged driving could lead to reduced performance or further damage to the DEF system.
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 often inexpensive, but diagnostic time may add to the cost.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.