Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2015 Subaru WRX BaseFACTORY OEM SERVICE PROCEDURE
Tire Pressure Monitor System (TPMS) DTCS
TIRE PRESSURE MONITOR SYSTEM (TPMS) DIAGNOSTIC TROUBLE CODE (DTC) LIST
| DTC | Item | Description |
|---|---|---|
| C2021 | Tire 1 Air Pressure Decrease | <Ref. to DTC C2021 TIRE 1 AIR PRESSURE DECREASE , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2022 | Tire 2 Air Pressure Decrease | <Ref. to DTC C2022 TIRE 2 AIR PRESSURE DECREASE , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2023 | Tire 3 Air Pressure Decrease | <Ref. to DTC C2023 TIRE 3 AIR PRESSURE DECREASE , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2024 | Tire 4 Air Pressure Decrease | <Ref. to DTC C2024 TIRE 4 AIR PRESSURE DECREASE , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2121 | Transmitter 1 No Data | <Ref. to DTC C2121 TRANSMITTER 1 NO DATA , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2122 | Transmitter 2 No Data | <Ref. to DTC C2122 TRANSMITTER 2 NO DATA , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2123 | Transmitter 3 No Data | <Ref. to DTC C2123 TRANSMITTER 3 NO DATA , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2124 | Transmitter 4 No Data | <Ref. to DTC C2124 TRANSMITTER 4 NO DATA , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2221 | Transmitter 1 Pressure Data Abnormal | <Ref. to DTC C2221 TRANSMITTER 1 PRESSURE DATA ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2222 | Transmitter 2 Pressure Data Abnormal | <Ref. to DTC C2222 TRANSMITTER 2 PRESSURE DATA ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2223 | Transmitter 3 Pressure Data Abnormal | <Ref. to DTC C2223 TRANSMITTER 3 PRESSURE DATA ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2224 | Transmitter 4 Pressure Data Abnormal | <Ref. to DTC C2224 TRANSMITTER 4 PRESSURE DATA ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2321 | Transmitter 1 Function Code Abnormal | <Ref. to DTC C2321 TRANSMITTER 1 FUNCTION CODE ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2322 | Transmitter 2 Function Code Abnormal | <Ref. to DTC C2322 TRANSMITTER 2 FUNCTION CODE ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2323 | Transmitter 3 Function Code Abnormal | <Ref. to DTC C2323 TRANSMITTER 3 FUNCTION CODE ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2324 | Transmitter 4 Function Code Abnormal | <Ref. to DTC C2324 TRANSMITTER 4 FUNCTION CODE ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2421 | Transmitter 1 Battery Voltage Decrease | <Ref. to DTC C2421 TRANSMITTER 1 BATTERY VOLTAGE DECREASE , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2422 | Transmitter 2 Battery Voltage Decrease | <Ref. to DTC C2422 TRANSMITTER 2 BATTERY VOLTAGE DECREASE , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2423 | Transmitter 3 Battery Voltage Decrease | <Ref. to DTC C2423 TRANSMITTER 3 BATTERY VOLTAGE DECREASE , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2424 | Transmitter 4 Battery Voltage Decrease | <Ref. to DTC C2424 TRANSMITTER 4 BATTERY VOLTAGE DECREASE , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
| C2521 | Vehicle Speed Is Abnormal | <Ref. to DTC C2521 VEHICLE SPEED IS ABNORMAL , Diagnostic Procedure with Diagnostic Trouble Code (DTC).> |
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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