OBD-II code · Powertrain (generic, extended)
P2040 Reductant Injection Air Pressure Sensor A Circuit High
The reductant injection air-pressure sensor A reads above its upper plausibility limit — open signal line or short to B+.
Is it safe to drive with P2040?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen signal line
- Less likelyConnector pins corroded - high contact resistance
- Less likelySupply wire pinched against B+ source
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)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.7–2 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Air Pressure Sensor
Related codes
- P2037Reductant Injection Air Pressure Sensor A Circuit
- P209DReductant Injection Air Pressure Sensor B Circuit High
- P203DReductant Level Sensor A Circuit High
- P203EReductant Level Sensor A Circuit Intermittent/Erratic
- P203FReductant Level Too Low
- P2041Reductant Injection Air Pressure Sensor A Circuit Intermittent
- P2042Reductant Temperature Sensor A Circuit
- P2043Reductant Temperature Sensor A Circuit Range/Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.