P01F3: O2 Sensor Circuit High Voltage Bank 1 Sensor 4

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. P01F3 means the signal is above about 1.05–1.1 V, which a switching sensor cannot produce – typically the heater supply or another voltage on the signal wire, or a heater-to-signal short inside the sensor.

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

• Signal wire shorted to heater supply or battery voltage
• Sensor faulty internally
• Sensor ground open (bias logic)

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the wiring and connector of the sensor indicated
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Look for exhaust leaks
4. Check the signal in live data with the engine warm
5. Check the fuse and the heater resistance if the code mentions it
6. Replace the sensor if it has power and does not respond

Good to know

• Repair difficulty: easy
• It affects emissions.

What each character of P01F3 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 1: Air and fuel
• F3: Specific fault in that system

Frequently asked questions

Can I keep driving with code P01F3?

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 P01F3?

The most common causes are: signal wire shorted to heater supply or battery voltage; sensor faulty internally; sensor ground open (bias logic).

Related codes

• P01F1O2 Sensor Circuit Bank 1 Sensor 4
• P01F2O2 Sensor Circuit Low Voltage Bank 1 Sensor 4
• P01F4O2 Sensor Circuit Slow Response Bank 1 Sensor 4
• P0144O2 Sensor Circuit High Voltage Bank 1 Sensor 3
• P0138O2 Sensor Circuit High Voltage 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.