Open or damaged wiring in the pressure sources switching valve circuit (broken wire, corroded connector); Failed pressure sources switching valve solenoid (open coil or shorted internally); Poor electrical connection at the valve connector or ECM connector; Short to battery voltage in the control wire between the ECM and the valve; Faulty ECM driver circuit (less common but possible); Contamination or mechanical binding of the valve causing abnormal current draw

DTC codes / Subaru codes / P1122

P1122 · SubaruPressure Sources Switching Valve Circuit High Input

Q: What does code P1122 mean?

Pressure Sources Switching Valve Circuit High Input. P1122 on a Subaru means the engine control module (ECM) has detected an abnormally high voltage on the pressure sources switching valve circuit, which is used to control vacuum routing for the differential pressure sensor. The ECM expects a certain voltage range from the valve solenoid, and a high reading indicates an open circuit, short to power, or a failed solenoid coil.

P1122 on a Subaru means the engine control module (ECM) has detected an abnormally high voltage on the pressure sources switching valve circuit, which is used to control vacuum routing for the differential pressure sensor. The ECM expects a certain voltage range from the valve solenoid, and a high reading indicates an open circuit, short to power, or a failed solenoid coil.

SystemPowertrain

Code typeSubaru specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Rough idle or stumbling if the valve failure affects vacuum routing to the pressure sensor
Poor fuel economy or reduced engine performance in some cases
A slight hesitation during acceleration when the ECM cannot correctly switch pressure sources
In rare cases, a stored code but no drivability issues at all

Common causes, most likely first

Open or damaged wiring in the pressure sources switching valve circuit (broken wire, corroded connector)
Failed pressure sources switching valve solenoid (open coil or shorted internally)
Poor electrical connection at the valve connector or ECM connector
Short to battery voltage in the control wire between the ECM and the valve
Faulty ECM driver circuit (less common but possible)
Contamination or mechanical binding of the valve causing abnormal current draw

How to diagnose and fix it

Verify the code with a scan tool and check for any related pending or stored codes
Inspect the pressure sources switching valve connector and wiring for corrosion, damage, or loose pins
Measure the resistance of the valve solenoid with a multimeter and compare to the manufacturer's specification
Check for battery voltage on the valve supply circuit with the key on, and check the control wire for a short to power
Test the control circuit from the ECM side for continuity and shorts, repairing any damaged wires
If the wiring and connections are good, replace the pressure sources switching valve
Clear the code and perform a test drive to confirm the repair, rechecking for any returning codes

What a high voltage really means here

A high voltage reading on this circuit almost always points to an open circuit or a failed solenoid coil rather than a short to ground, which would set a low voltage code instead.
The pressure sources switching valve is often misdiagnosed as a faulty differential pressure sensor, but the sensor itself rarely causes this specific code.
Corroded or loose connectors at the valve are a common cause on older Subarus, especially in areas with road salt exposure.
The ECM may set this code intermittently if the wiring harness has a chafe point that only opens the circuit during certain engine movements.
Do not overlook the ground circuit for the valve; a poor ground can cause the ECM to see a high voltage on the control side.

Can I keep driving with P1122?

You can generally continue driving with this code, but avoid heavy acceleration or towing until it is repaired, as the engine may not manage vacuum routing correctly and could affect emissions or performance.

Tools that help

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