Reductant Injection Air Pressure Sensor A Circuit Range/Performance
What it means
P2038 means the reductant (DEF) injection air pressure sensor "A" is reading outside its expected range on a diesel SCR system. This sensor monitors the air pressure that helps atomize diesel exhaust fluid into the exhaust. A range/performance fault mainly affects emissions control, but diesels often respond with a power derate and warnings if it isn't fixed. The engine still starts and runs.
Can I keep driving? Drivable at first, but diesel SCR faults often trigger a power derate and countdown to no-restart; have it fixed promptly.
Real-world scan data
Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.
Common symptoms
What you'll notice
- Check-engine light on
- SCR / emissions system or DEF warning message
- Reduced engine power (derate) if the fault persists
- Possible increase in tailpipe NOx / failed emissions test
Common causes
Most likely first
- Reductant injection air pressure sensor A out of range or driftingLikely
- Damaged wiring or corroded connector at the sensorCommon
- Restricted, leaking, or disconnected air-assist line to the reductant systemCommon
- Faulty air-assist pump or pressure regulatorLess often
- Faulty PCM/DEF control module (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and compare the sensor's live pressure reading to actual system pressure.
- Inspect the sensor wiring, connector, and air-assist plumbing for leaks or blockages.
- Repair any wiring fault, air leak, or restriction found.
- Replace the reductant injection air pressure sensor A if it reads out of range.
- Clear the code and re-test; the control module is a last resort after the circuit and plumbing check out.
FAQ
Quick answers
Is it safe to drive with P2038?+
Can I just clear P2038?+
Related codes
Read & clear P2038 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.