Open or shorted wiring in the reductant injection air pressure control valve circuit; Corroded or loose electrical connector at the valve; Failed reductant injection air pressure control valve solenoid; Blown fuse or relay supplying power to the valve circuit; Faulty powertrain control module (rare); Damage to the wiring harness from heat, vibration, or debris

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P20A6

P20A6Reductant Injection Air Pressure Control Valve Circuit/Open

Q: What does code P20A6 mean?

Reductant Injection Air Pressure Control Valve Circuit/Open. P20A6 indicates that the powertrain control module has detected an open circuit or electrical fault in the reductant injection air pressure control valve circuit, which is part of the diesel exhaust fluid (DEF) injection system on selective catalytic reduction (SCR) equipped vehicles. The computer monitors the valve's electrical circuit and sets this code when the expected voltage or current is outside the normal range, typically indicating a broken wire, poor connection, or failed valve solenoid.

P20A6 indicates that the powertrain control module has detected an open circuit or electrical fault in the reductant injection air pressure control valve circuit, which is part of the diesel exhaust fluid (DEF) injection system on selective catalytic reduction (SCR) equipped vehicles. The computer monitors the valve's electrical circuit and sets this code when the expected voltage or current is outside the normal range, typically indicating a broken wire, poor connection, or failed valve solenoid.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine power or limp mode in some vehicles
Increased diesel exhaust fluid consumption
Rough running or hesitation during regeneration cycles
A warning message on the dashboard indicating an emissions system fault

Common causes, most likely first

Open or shorted wiring in the reductant injection air pressure control valve circuit
Corroded or loose electrical connector at the valve
Failed reductant injection air pressure control valve solenoid
Blown fuse or relay supplying power to the valve circuit
Faulty powertrain control module (rare)
Damage to the wiring harness from heat, vibration, or debris

How to diagnose and fix it

Perform a visual inspection of the valve, connector, and wiring for obvious damage or corrosion
Check the fuse and relay related to the reductant injection air pressure control valve circuit
Use a scan tool to command the valve on and off and listen for activation
Measure resistance across the valve solenoid and compare to manufacturer specifications
Check for voltage and ground signals at the valve connector with the key on and engine off
Perform a voltage drop test on the power and ground circuits to identify high resistance
If all electrical checks pass, suspect the powertrain control module and perform further diagnostics

Common Misdiagnosis Traps for P20A6

A loose or corroded connector is often the root cause, so always inspect and clean the terminals before replacing the valve.
The code can be set by a faulty fuse or relay that is shared with other circuits, so check those first.
Some vehicles require a relearn or adaptation reset after repairing the circuit, so consult the service manual.
The reductant injection air pressure control valve is sometimes confused with the reductant injector, but they are separate components.
In rare cases, a software glitch in the powertrain control module can trigger this code, so check for technical service bulletins.

Can I keep driving with P20A6?

You can usually continue driving with this code, but the vehicle may enter limp mode or fail an emissions test. Avoid long trips and schedule repairs promptly to prevent further damage to the SCR system.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.