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 pump. This can lead to improper DEF injection, affecting emissions and potentially triggering the check engine light.
01. Most Common Causes
- Faulty reductant injection air pressure sensor
- Open or shorted wiring in the sensor circuit
- Poor electrical connection at the sensor
- Failed reductant injection pump
02. Symptoms You Will Notice
- Check engine light illuminated
- Reduced engine performance
- Increased emissions
- Possible diesel exhaust fluid (DEF) system warning
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 and wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's voltage and ground circuits with a multimeter; compare to manufacturer specifications.
Step 4: If wiring is intact, replace the reductant injection air pressure sensor.
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 the vehicle may fail emissions tests and could enter limp mode. Prolonged driving may cause further damage to the DEF system.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and sensor replacement, but can be higher if the pump or wiring needs repair.