Emissions

P01F2 — O2 Sensor Circuit Low Voltage, Bank 1 Sensor 4

Severity: low Safe to drive

What P01F2 means

The engine control module detected that the signal in the Bank 1 Sensor 4 oxygen sensor circuit is too low. This is typically an additional downstream sensor behind the main catalytic converter or further along the exhaust, used to monitor catalyst performance and help fine-tune the mixture. Sensor numbering depends on the engine layout, so confirm the exact location for your vehicle.

Symptoms

  • Check engine light on
  • Often no change in how the engine runs
  • Possible increase in fuel consumption
  • Possible rough or unstable idle
  • Higher emissions on a test

Possible causes

  1. Failed or aged Bank 1 Sensor 4 oxygen sensor
  2. Damaged, shorted to ground, or corroded wiring or connector
  3. Sensor heater circuit fault
  4. Exhaust leak near the sensor
  5. Mixture problem upstream of the sensor
  6. ECM fault (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and note any fuel trim or catalyst codes
  2. Find out from a diagram where Sensor 4 sits on your engine
  3. Inspect the sensor, harness, and connector for chafing, melting, corrosion, or moisture
  4. Watch the sensor signal in live data and see how it responds to changes
  5. Test power, heater circuit, and ground at the connector with a multimeter
  6. Check the exhaust for leaks near the sensor
  7. Review short and long term fuel trims for mixture issues
  8. If wiring and power are good, replace the sensor and see if the code returns

Common fixes

  • Replace the Bank 1 Sensor 4 oxygen sensor
  • Repair the wiring or connector
  • Fix the exhaust leak
  • Correct any underlying mixture fault found
  • Reflash or replace the ECM only after everything else is ruled out

Questions and answers

Can I drive with code P01F2?

Usually yes, for a short time. Still, fix it soon so you do not miss a hidden mixture or catalyst problem.

What does Sensor 4 mean in P01F2?

It is the fourth oxygen sensor in Bank 1 of the exhaust, typically located after the main catalytic converters. The exact position depends on the engine, so check a diagram.

Is replacing the sensor always the fix?

No. Check the wiring, connector, and exhaust leaks first, otherwise a new sensor may set the same code.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.