Failed or contaminated intake manifold pressure sensor; Damaged or corroded sensor connector pins or terminals; Open or shorted wire in the sensor signal or ground circuit; Vacuum hose or boost hose disconnected, cracked, or leaking; Clogged or restricted pressure sensor port in the intake manifold; Faulty ECM driver circuit (rare but possible after other causes are ruled out)

DTC codes / Subaru codes / P1143

P1143 · SubaruPressure Sensor Circuit Low Input

Q: What does code P1143 mean?

Pressure Sensor Circuit Low Input. P1143 on a Subaru means the engine control module (ECM) has detected a low input voltage from the pressure sensor circuit, which on turbocharged models is the intake manifold pressure sensor. The ECM expects a voltage signal that rises with boost pressure, but the signal is stuck below the normal range, so the computer flags the circuit as faulty.

P1143 on a Subaru means the engine control module (ECM) has detected a low input voltage from the pressure sensor circuit, which on turbocharged models is the intake manifold pressure sensor. The ECM expects a voltage signal that rises with boost pressure, but the signal is stuck below the normal range, so the computer flags the circuit as faulty.

SystemPowertrain

Code typeSubaru specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Check engine light illuminated, often with no other noticeable symptoms
Reduced engine power or limp mode on turbocharged models
Poor fuel economy or rich-running condition
Hesitation or stumble during acceleration
Rough idle or unstable idle quality
On some models, a slight whistle or boost leak noise under load

Common causes, most likely first

Failed or contaminated intake manifold pressure sensor
Damaged or corroded sensor connector pins or terminals
Open or shorted wire in the sensor signal or ground circuit
Vacuum hose or boost hose disconnected, cracked, or leaking
Clogged or restricted pressure sensor port in the intake manifold
Faulty ECM driver circuit (rare but possible after other causes are ruled out)

How to diagnose and fix it

Inspect the pressure sensor connector and wiring for corrosion, looseness, or damage
Check the vacuum/boost hose between the sensor and intake manifold for cracks or disconnection
Measure sensor reference voltage and signal voltage with a multimeter and compare to specification
Verify sensor ground circuit integrity with a voltage drop test
Remove and inspect the pressure sensor for contamination or a blocked port, clean or replace as needed
Clear the code and perform a road test to confirm the repair, monitoring live data for proper pressure readings
If the circuit tests good but the code persists, check for a faulty ECM after ruling out all other causes

What most technicians miss on P1143

A loose or cracked vacuum hose at the pressure sensor is a far more common cause than a failed sensor itself, and it often sets this code without any driveability complaint.
The pressure sensor on Subaru turbo engines shares its reference voltage with other sensors, so a short in a neighbouring circuit can drag the signal low and mimic a failed sensor.
Oil contamination from the PCV system can coat the sensor element and cause a low signal that looks like an electrical fault, so always inspect the sensor tip before condemning it.
On some Subaru models, the same code can be set by a poor ground connection at the intake manifold rather than by the sensor or its wiring, so a voltage drop test on the ground side is essential.
Clearing the code without repairing the root cause often leads to a repeat failure within a few drive cycles, especially if a boost leak is left unresolved.

Can I keep driving with P1143?

You can usually drive the vehicle to a repair shop, but avoid heavy acceleration and sustained boost until the fault is fixed, because the ECM may be running a default fuel map that can cause rich running or reduced power. If the engine enters limp mode or runs poorly, stop driving and have it towed.

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.