Reductant Injection Air Pressure Sensor Circuit Low
The P2039 code means the vehicle's onboard diagnostic system has detected: Reductant Injection Air Pressure Sensor Circuit Low. This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $200 - $600 (parts and labor)
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Common Symptoms
- Check Engine Light on
- DEF system malfunction indicator
- Engine power reduction
- SCR system not functioning
- Possible speed limiter activation
Probable Causes (Ranked by Likelihood)
- Short to ground in air pressure sensor circuit Very High
- Failed air pressure sensor High
- Water intrusion in sensor connector Moderate
- Damaged wiring near exhaust heat Moderate
- PCM input circuit fault Low
Frequently Asked Questions
What does P2039 mean?
P2039 indicates the reductant injection air pressure sensor circuit is reading below the minimum voltage, usually from a wiring short to ground or sensor failure.
Can I drive with a P2039 code?
Drive only short distances. The SCR system will not function, and some vehicles may activate a speed limiter if not repaired promptly.
How much does it cost to fix P2039?
Repair costs are typically $200 to $600 for sensor or wiring repair.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Confirm P2039 with freeze frame data
-
Check air pressure sensor connector for moisture or corrosion
-
Measure sensor signal voltage at connector
-
Inspect wiring for shorts to ground
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Commonly Affected Vehicles
- 2011-2019 Chevrolet Silverado 2500 6.6L Duramax
- 2009-2015 Volkswagen Jetta 2.0L TDI
- 2012-2018 BMW 328d 2.0L Diesel
- 2010-2016 Mercedes-Benz ML350 3.0L BlueTEC
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