P0231 on Subaru
Fuel Pump Secondary Circuit - Low
P0231 on Subaru vehicles indicates fuel pump secondary circuit - low. Au7o has documented this code across 2 Subaru models — most commonly on Ascent, Crosstrek. This code indicates the engine computer detected a low-voltage condition in the fuel pump's secondary (driver/output) control circuit. Many vehicles control the fuel pump through a relay or a dedicated driver module, and the computer monitors the voltage on that circuit to confirm the pump is being powered correctly. When the feedback voltage stays lower than expected, P0231 sets. Because the fuel pump supplies pressurized fuel to the injectors, this fault can cause hard starting, stalling, or no-start conditions.
Common Causes of P0231
- •Faulty fuel pump relay
- •Corroded or loose connector at the pump or relay
- •Damaged or shorted wiring in the pump power circuit
- •Poor ground for the fuel pump circuit
- •Failing fuel pump drawing abnormal current
- •Faulty fuel pump driver module
- •PCM/ECM internal driver fault (rare)
P0231 on Subaru by Model
Subaru Ascent(1 issue)
- Fuel Pump Impeller Failure - Recall WRK-22 / NHTSA 20V-7012019-2021
Certain 2019-2021 Ascents are affected by a fuel pump recall (WRK-22, NHTSA 20V-701) where the low-pressure fuel pump impeller can deform due to excessive absorption of fuel components, particularly in regions with higher-concentration ethanol fuels. A deformed impeller reduces fuel delivery, causing engine stalling, rough running, or inability to start. This is a safety concern as stalling can occur without warning during driving. The recall was coordinated across multiple manufacturers using the same Denso fuel pump.
Subaru Crosstrek(1 issue)
- Denso Low-Pressure Fuel Pump Impeller Failure Causing Stall2019
2019 Crosstreks (along with various 2013-2020 Subarus) were built with Denso low-pressure in-tank fuel pumps whose plastic impeller absorbs fuel and swells. The swollen impeller binds against the pump body, causing rough running, no-start, and unexpected engine stalls at highway speed. Affected vehicles were subject to NHTSA recalls (including WRD-20); related class-action litigation remains pending (Seeger Weiss case 1:20-cv-0982, D.N.J.).
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View P0231 across all makes →Frequently Asked Questions
What does P0231 mean on Subaru?▼
P0231 stands for "Fuel Pump Secondary Circuit - Low." This code indicates the engine computer detected a low-voltage condition in the fuel pump's secondary (driver/output) control circuit. Many vehicles control the fuel pump through a relay or a dedicated driver module, and the computer monitors the voltage on that circuit to confirm the pump is being powered correctly. When the feedback voltage stays lower than expected, P0231 sets. Because the fuel pump supplies pressurized fuel to the injectors, this fault can cause hard starting, stalling, or no-start conditions. On Subaru specifically, this code is documented across 2 models.
What causes P0231 on Subaru vehicles?▼
Common causes on Subaru: Faulty fuel pump relay, Corroded or loose connector at the pump or relay, Damaged or shorted wiring in the pump power circuit, Poor ground for the fuel pump circuit, Failing fuel pump drawing abnormal current. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0231 on a Subaru?▼
Repair costs vary widely depending on the root cause and specific Subaru model.
Which Subaru models have P0231 documented?▼
Au7o has documented P0231 on 2 Subaru models: Ascent, Crosstrek.