P2040: Reductant Injection Air Pressure Sensor A Circuit High
What to do
The car drives normally for now. Worth repairing before the system decides it cannot dose at all — see P2047 for what happens then, because it is not a fault that stays quiet.
What this code means
The reductant injection air pressure circuit reads above its valid range — an open circuit or a short to supply, which the module cannot distinguish between. On a sensor mounted around the exhaust and underbody, a connector corroded by road spray reads identically to a broken wire and is the more likely of the two.
Likely causes
Start here
- Open circuit in sensor wiring · moderate
- Corroded or loose connector · easy
- Faulty reductant injection air pressure sensor · moderate
Less common
- Wiring shorted to voltage · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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