The P2038: Reductant Injection Air Pressure Sensor ‘A’ Circuit Range/Performance code indicates that the air pressure sensor in the reductant injection system (DEF/AdBlue) is not performing within the expected range. This issue could be caused by a faulty sensor, performance issues, or wiring and connector problems.
P2038 – Quick Overview
Code | Information |
---|---|
Meaning | P2038: Reductant Injection Air Pressure Sensor ‘A’ Circuit Range/Performance |
Is it serious? | Yes, this issue can impair the DEF injection system, leading to poor NOx reduction and potentially increased emissions. |
Possible causes | – Faulty air pressure sensor – Incorrect sensor performance – Wiring or connector issues |
How to diagnose? | – Test the sensor for range and performance – Inspect wiring and connectors – Verify sensor operation |
P2038 Meaning
The P2038: Reductant Injection Air Pressure Sensor ‘A’ Circuit Range/Performance code means that the air pressure sensor in the reductant injection system is not providing readings within the expected range. The air pressure sensor helps maintain the correct air pressure for the DEF injection system to function properly. When the sensor fails or the circuit is compromised, the DEF injection may become inefficient, resulting in poor emissions control.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for additional codes related to the reductant system. Other codes may provide more information on related faults. | OBD-II Scanner |
Test the Air Pressure Sensor | Use a multimeter or diagnostic tool to test the air pressure sensor’s range and performance. Compare the sensor’s readings with the manufacturer’s specifications to determine if it is functioning correctly. | Multimeter, Diagnostic Tool |
Inspect Wiring and Connectors | Visually inspect all wiring and connectors leading to the air pressure sensor for signs of damage, corrosion, or disconnections that could impact the sensor’s performance. | Flashlight, Multimeter |
Check Sensor Circuit Continuity | Perform a continuity test on the wiring connected to the air pressure sensor to ensure there are no shorts, breaks, or high resistance affecting the sensor’s performance. | Multimeter |
Verify Sensor Calibration | Use a diagnostic tool to ensure that the air pressure sensor is correctly calibrated. An incorrectly calibrated sensor may cause improper readings, leading to the P2038 code. | Diagnostic Tool |
Inspect Reductant Injection System | Check the reductant injection system, including air lines, valves, and other components, to ensure the system is maintaining the correct air pressure and is not blocked or damaged. | Flashlight, Air Pressure Gauge |
Replace the Air Pressure Sensor | If the sensor is faulty or performing outside the specified range, replace it with a new one. Make sure the replacement sensor is installed properly to prevent future issues. | Replacement Air Pressure Sensor, Wrench |
Repair or Replace Damaged Wiring | Repair or replace any faulty wiring, connectors, or circuit components to restore proper operation of the air pressure sensor. | Wiring Repair Kit |
Clear the Code and Test Drive | After completing the repairs, clear the P2038 code using an OBD-II scanner. Take the vehicle for a test drive to ensure the issue has been resolved and the sensor is performing within range. | OBD-II Scanner, Vehicle Owner’s Manual |
Recheck for Codes | After the test drive, re-scan the vehicle to verify that the P2038 code has not returned. | OBD-II Scanner |

OBD-II scanner Buyer’s Guide
- Scanner features explained
- Different types of scanners
- Scanners for coding/odometer/ECU/checks
- Best picks + discount codes

Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)