P2037: Reductant Injection Air Pressure Sensor A Circuit
What to do
Have this seen to promptly even though the car drives normally now. Urea that is not injected properly crystallises into a hard deposit that blocks the system, and that damage accumulates — and once the vehicle decides it cannot dose at all, the law requires it to restrict or prevent operation, so this is a fault that eventually stops the car.
What this code means
A fault in the sensor monitoring air pressure in the reductant injection system — the arrangement that meters urea solution into the exhaust so that selective catalytic reduction can convert oxides of nitrogen into nitrogen and water.
Some systems atomise the urea using compressed air rather than pressure alone, and this sensor confirms that air is available at the right pressure. Without atomisation the dose lands as liquid rather than mist, which is the beginning of the characteristic failure of every urea system: crystallisation. Urea solution that is not fully vaporised leaves a hard white deposit that builds on the injector tip and inside the pipe, progressively restricting it until nothing gets through.
That matters because crystallisation is cumulative and largely preventable. A dosing fault caught early is a sensor; the same fault left alone becomes a blocked injector and a crystallised pipe, and eventually a vehicle that will not start because the law requires these systems to inhibit operation when they cannot dose.
Likely causes
Start here
- Faulty reductant injection air pressure sensor · moderate
- Corroded or loose connector · easy
- Restricted reductant injection air line · moderate
Less common
- Crystallised reductant deposits · specialist
- Open circuit in sensor wiring · moderate
Symptoms
Components involved
Information, not instruction
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Community experience
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