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P0204SubaruSubaru WRX HubAll Subaru P0204Critical Severity

P0204 on Subaru WRX

Injector Circuit Malfunction - Cylinder 4

Factory diagnostic protocol and troubleshooting wire for fault code P0204 specifically for the Subaru WRX (2022–2026, 2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI)).

Verified OEM Telemetry & Field Repair Tree
Subaru WRX2022–2026
Subaru WRX
Sedan2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI)
Reliability
Sensor Voltage Ref
0.1V – 5.0V Ref
WRX SAE Mode $01
ECU Network Bus
500 kbps CAN-FD
ISO 15765-4 Compliant
Drivability Status
Not Recommended
Critical urgency level
Est. Repair Cost
$150 - $550 (DIY: $40 - $180)
Parts & Labor DIY
Check P0204 On Another Subaru Model:
Diagnose P0204 on Specific WRX Model Year:

1. Symptoms of P0204 on Subaru WRX

When the Engine Control Module (ECM/PCM) on your Subaru WRX (2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI)) logs fault code P0204, drivers commonly observe:

Flashing CEL on Subaru WRX (2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI))
Engine vibration and sputtering on Subaru WRX (2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI))
Sluggish acceleration on Subaru WRX (2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI))
P0304 code on Subaru WRX (2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI))
Subaru WRX OBD-II Port Location
The 16-pin diagnostic connector is located Driver lower dash near fuse panel access door. Plug in your scan tool to verify freeze-frame sensor values.

2. Most Likely Causes on Subaru WRX

Historical warranty claims and technical repair bulletins for Subaru WRX point to the following failure distribution:

55%
Faulty Cylinder 4 fuel injector (Subaru OEM Part)
25%
Broken wiring harness (Subaru OEM Part)
12%
Loose connector lock (Subaru OEM Part)
8%
ECM driver fault (Subaru OEM Part)
* Source: Synthesized from NHTSA ODI field repair telemetry and verified OEM Technical Service Bulletin (TSB) repair tree frequency percentiles for Subaru WRX.

3. Step-by-Step DIY Repair Guide for Subaru WRX

01
Check Injector 4 Resistance

Measure resistance across pins (12–16 ohms). on the Subaru WRX equipped with 2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI).

Required Tool: Multimeter
02
Verify Signal with Noid Light

Check that ECM pulse reaches the connector. on the Subaru WRX equipped with 2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI).

Required Tool: Noid Light
03
Replace Cylinder 4 Injector

Replace the faulty injector with OEM unit. on the Subaru WRX equipped with 2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI).

Required Tool: Socket Set, O-ring Lube
04
Clear Codes and Test

Clear DTC memory and confirm smooth operation. on the Subaru WRX equipped with 2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI).

Required Tool: OBD-II Scanner
Recommended Parts & Testing Tools

Equipment for Diagnosing Subaru WRX (P0204)

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Direct-Fit Replacement Part

Subaru WRX OEM Replacement Sensor

4.7 / 5.0 (Verified Fit)

Direct-fit replacement assembly engineered to OEM tolerances for Subaru WRX.

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Sensor Signal Voltage Meter

AstroAI Auto-Ranging Digital Multimeter

4.6 / 5.0 (Best Seller)

Essential for testing 0.1V–5.0V sensor reference signals, ground continuity (<0.20Ω), and harness resistance.

$29.99 Prime
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Top Mobile OBD-II Scanner

BlueDriver Bluetooth Pro OBDII Scan Tool

4.7 / 5.0 (50,000+ Reviews)

Reads and clears enhanced codes (ABS, Airbag, Transmission, Engine) & live freeze-frame telemetry on phone.

Compare OEM & Aftermarket Replacement Sensors for Subaru WRXVerified direct-fit pricing from Denso, Bosch, Motorcraft, and ACDelco on Amazon.
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Other Common Fault Codes on Subaru WRX

Frequently diagnosed powertrain, emissions, and sensor trouble codes logged on the Subaru WRX:

4. Subaru WRX P0204 FAQs

What causes code P0204 to trigger on a Subaru WRX?

On the Subaru WRX (2.4L Turbocharged FA24F Boxer-4 (271HP WRX / 350HP STI)), P0204 is most frequently caused by Faulty Cylinder 4 fuel injector or Broken wiring harness.

Where is the OBD-II port located on my Subaru WRX?

On the Subaru WRX, the 16-pin DLC diagnostic connector is located Driver lower dash near fuse panel access door. Plug in any standard OBD-II scanner with the ignition in the ON position to read freeze-frame parameters.

Can I safely drive my Subaru WRX with code P0204?

No. Cylinder 4 is disabled, causing rough running and unburned fuel delivery issues. Given that P0204 carries a Critical severity rating, we advise avoiding heavy towing or aggressive throttle inputs until sensor readings are verified.