Reductant Injection Air Pressure Sensor Circuit High
The P2040 code means the vehicle's onboard diagnostic system has detected: Reductant Injection Air Pressure Sensor Circuit High. 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 warning light
- Engine power derate
- SCR system malfunction
- Speed limiter may engage
Probable Causes (Ranked by Likelihood)
- Short to voltage in air pressure sensor wiring Very High
- Defective air pressure sensor High
- Open ground in sensor circuit Moderate
- Corroded connector pins Moderate
- PCM input driver failure Low
Frequently Asked Questions
What does P2040 mean?
P2040 means the reductant injection air pressure sensor is reading above the maximum expected voltage, typically from a wiring short to voltage or failed sensor.
Can I drive with a P2040 code?
Drive only short distances. The DEF injection system cannot function correctly, and a speed limiter countdown may start on some vehicles.
How much does it cost to fix P2040?
Expect $200 to $600 for sensor replacement or wiring repair.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Read freeze frame data and confirm P2040
-
Check air pressure sensor wiring for shorts to battery voltage
-
Measure sensor circuit voltage and ground integrity
-
Test sensor with known good pressure source
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
- 2009-2015 Volkswagen Jetta 2.0L TDI
- 2012-2018 BMW 328d 2.0L Diesel
- 2010-2016 Mercedes-Benz ML350 3.0L BlueTEC
- 2014-2020 Ram 3500 6.7L Cummins
Related Codes
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