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.
2018 Subaru WRX STIFACTORY OEM SERVICE PROCEDURE
Drive Cycle B
| DTC | Item | Condition |
|---|---|---|
| P0125 | INSUFFICIENT COOLANT TEMPERATURE FOR CLOSED LOOP FUEL CONTROL | «Coolant Temp.» at engine start: Less than -15°C (5°F) |
| P0137 | O2 SENSOR CIRCUIT LOW VOLTAGE BANK 1 SENSOR 2 | - |
| P0138 | O2 SENSOR CIRCUIT HIGH VOLTAGE BANK 1 SENSOR 2 | - |
| P0171 | SYSTEM TOO LEAN BANK 1 | Complete diagnosis with drive cycle A as well. |
| P0172 | SYSTEM TOO RICH BANK 1 | Complete diagnosis with drive cycle A as well. |
| P0300 | RANDOM/MULTIPLE CYLINDER MISFIRE DETECTED | Complete diagnosis with drive cycle A as well. |
| P0301 | CYLINDER 1 MISFIRE DETECTED | Complete diagnosis with drive cycle A as well. |
| P0302 | CYLINDER 2 MISFIRE DETECTED | Complete diagnosis with drive cycle A as well. |
| P0303 | CYLINDER 3 MISFIRE DETECTED | Complete diagnosis with drive cycle A as well. |
| P0304 | CYLINDER 4 MISFIRE DETECTED | Complete diagnosis with drive cycle A as well. |
| P0500 | VEHICLE SPEED SENSOR "A" CIRCUIT | - |
| P0506 | IDLE CONTROL SYSTEM RPM - LOWER THAN EXPECTED | - |
| P0507 | IDLE CONTROL SYSTEM RPM - HIGHER THAN EXPECTED | - |
| P2096 | POST CATALYST FUEL TRIM SYSTEM TOO LEAN BANK 1 | Complete diagnosis with drive cycle A as well. |
| P2097 | POST CATALYST FUEL TRIM SYSTEM TOO RICH BANK 1 | Complete diagnosis with drive cycle A as well. |
Diagnostic procedure:Â
- Drive at 10 km/h (6 MPH) or more.
- Stop the vehicle and idle for ten minutes.
- Read the temporary code using the Subaru Select Monitor or general scan tool. Ref. to ENGINE (DIAGNOSTICS) (STI)>Read Diagnostic Trouble Code (DTC)>OPERATIONÂ .
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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