Sensor 4 on bank 1 is a fourth oxygen sensor, behind a third converter or converter brick. The OBD standard provides for up to four sensors per bank, and the code standard defines sensor 4 for bank 1 only. No manufacturer or vehicle using these codes could be identified; the description rests on CARB's requirements for downstream oxygen sensors and the logic of sensors 2 and 3. A switching sensor delivers about 0.1–0.9 V. P01F1 is the general circuit code of this sensor, the counterpart of P0136/P0142 for sensors 2 and 3. Typical causes are an aged sensor, open or high-resistance wiring and a failed heater.
Medium severity. Can I keep driving?Yes, you can normally drive in moderation, but get it repaired soon: you will use more fuel and the catalytic converter can be damaged over time.
Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.
Symptoms
- Check engine light on (usually after two drive cycles)
- Catalyst monitor readiness possibly not set
- Usually no change in driving
Most likely causes
- Sensor 4 aged or poisoned
- Wiring or connector open, high-resistance or corroded
- Sensor heater failed
- Control module
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
- It affects emissions.
What each character of P01F1 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- F1: Specific fault in that system
Frequently asked questions
Can I keep driving with code P01F1?
Yes, you can normally drive in moderation, but get it repaired soon: you will use more fuel and the catalytic converter can be damaged over time.
What causes code P01F1?
The most common causes are: sensor 4 aged or poisoned; wiring or connector open, high-resistance or corroded; sensor heater failed.
Related codes
- P01F2O2 Sensor Circuit Low Voltage Bank 1 Sensor 4
- P01F3O2 Sensor Circuit High Voltage Bank 1 Sensor 4
- P01F4O2 Sensor Circuit Slow Response Bank 1 Sensor 4
- P0142O2 Sensor Circuit Bank 1 Sensor 3
- P0136O2 Sensor Circuit Bank 1 Sensor 2
Sources
- law.cornell.edu: 13 CCR 1968.2
- en.wikipedia.org: Oxygen sensor
- gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.