P2004 on Subaru: How to Diagnose & Fix
Intake Manifold Runner Control Stuck Open (Bank 1)
2 Subaru models · 2 documented issues · $250-$1,400 repair
P2004 on Subaru by model: symptoms, diagnosis and fix
WRX STI models with EJ257 intake TGV assemblies can develop failures in the TGV position sensors or actuator mechanisms, leading to stuck-open/stuck-closed conditions. Owners report check engine lights, rough cold starts, and reduced drivability, especially in colder weather. This issue is frequently discussed in owner reports and appears in diagnostic guidance/TSBs for Subaru intake runner control/TGV-related DTCs.
Common Symptoms
- Check Engine Light with TGV-related codes
- Rough idle or stumbling on cold start
- Reduced throttle response
- Poor fuel economy
- Intermittent hesitation at low RPM
How to Fix
Scan for TGV-related codes and verify actuator movement and sensor feedback; repair wiring/connectors as needed. Replace the affected TGV assembly or sensor/motor components and perform ECU relearn procedures per Subaru service manual; ensure no intake vacuum leaks after reassembly.
Sources for this issue (1)
Turbo WRX intake manifolds carry tumble generator valves — butterfly plates in each runner driven by a small electric actuator with a position sensor. The original valve shaft material corrodes from EGR/condensation and binds, or the actuator motor/sensor fails, and the ECU logs TGV stuck-open/stuck-closed codes (P2004-P2007, sometimes P2016/P2017 position sensor codes). The car goes into a reduced-power mode. Subaru acknowledged the shaft corrosion in TSB 02-182-19 and revised the shaft material. It affects both the EJ255 (2008-2014) and FA20DIT (2015-2021) WRX, with separate part numbers per engine.
Common Symptoms
- Check engine light with P2004-P2007
- Significant loss of power / limp mode
- Rough idle
- Intermittent code that returns after clearing
How to Fix
Confirm by disconnecting the actuator and rotating the valve by hand — a gritty or stuck shaft means the TGV assembly is seized. Replace the affected TGV assembly with the revised-shaft part (Subaru does not sell the motor or sensor separately). Some owners delete TGVs with aftermarket housings, which requires a tune. Out of warranty there is no free remedy; the TSB is a diagnostic aid, not a campaign.
Sources for this issue (3)
P2004 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P2004 mean on a Subaru?
P2004 stands for "Intake Manifold Runner Control Stuck Open (Bank 1)." P2004 means the intake manifold runner control for engine bank 1 is stuck in the open position. Many engines use flaps or valves inside the intake manifold that close at low RPM to boost air velocity and torque, then open at higher RPM; this code sets when the computer commands those runners to close but a sensor shows they remain open. The result is usually rough low-speed running, reduced low-end power, or hesitation. It indicates a mechanical or actuator problem in the variable intake system, not a true vacuum or fuel issue. On Subaru it is documented across 2 models: WRX STI, WRX.
What are the most common causes of P2004?
The most common causes of P2004 are: Stuck or seized intake manifold runner flaps (carbon buildup), Failed intake manifold runner control actuator or solenoid, Disconnected or broken actuator linkage/rod, Faulty intake runner position sensor, Damaged wiring or connector at the actuator/sensor, Vacuum leak or failed vacuum supply on vacuum-operated systems, Cracked or warped intake manifold. The specific cause varies by vehicle.
How much does it cost to fix P2004 on a Subaru?
Published repair estimates on Subaru range from $250 to $1,400 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P2004 on a different make?
View P2004 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.