What it means
A general electrical fault is reported on reductant injection air-pressure sensor A — used on air-assisted DEF dosing systems to monitor the atomisation air pressure delivered to the injector.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
On air-assisted DEF systems, sensor A reports the air pressure used to atomise reductant at the injector. The control module monitors its electrical signal and sets P2037 when it detects a general fault in that sensor circuit, rather than a specifically low or high reading.
Common causes
Most likely first.
- Air pressure sensor failed
- Harness fault between sensor and PCM
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Record freeze-frame data and check live reductant air-pressure data for sensor A to see whether the fault is present now or intermittent.
- Inspect sensor A's connector and harness for loose pins, corrosion, damaged insulation, or contact with hot or moving parts.
- With the ignition off, check the sensor and circuit connections against the vehicle wiring diagram before disconnecting or testing them.
- Measure the circuit supply, ground, and signal at sensor A and at the control-module end, comparing results with the manufacturer's specification.
- If wiring and connections pass, test sensor A's response while the system operates and replace it only if its output is faulty.
Common fixes
- Clean and secure the sensor A connector.
- Repair an open, short, or damaged section of the sensor harness.
- Replace a failed reductant injection air-pressure sensor A.
Can I keep driving?
You can usually drive cautiously if the vehicle runs normally, but arrange diagnosis soon and watch for DEF warnings or a start countdown. A dosing fault can raise NOx emissions and may eventually prevent restarting.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.