The upstream oxygen sensor (sensor 1, before the catalytic converter) is the main control sensor for the air-fuel mixture. 'Slow response' means the signal transition itself is too sluggish – it takes too long to pass between two voltage levels. This code covers the rich-to-lean direction, usually tested during deceleration fuel cut-off. Bank 2 only exists on V and boxer engines. No manufacturer document using exactly this code was found. The principle is known from wide-band sensor tests: the control module modulates the mixture and evaluates the sensor's response time in each direction (Ford, Siemens patent) – Ford, however, reports such faults for bank 2 as P0153. CARB requires separate detection of slow and delayed faults in each direction (phased in from 2009 for downstream and 2011 for upstream sensors).
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 2 is the side without cylinder 1, so it only exists on V or boxer engines. Sensor 1 is the oxygen sensor before the catalytic converter.
Symptoms
- Check engine light on
- Slightly higher consumption or rough idle possible
- Higher emissions, possible emissions test failure
- Often no noticeable symptoms
Most likely causes
- Upstream oxygen sensor aged or poisoned (silicone, oil, coolant, soot)
- Exhaust leak ahead of the sensor (manifold, flange)
- Mixture fault: intake air leak, injectors, fuel pressure, air flow sensor
- Sensor heater weak, sensor too cold
- Connector, wiring or control module software
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 P014E means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 1: Air and fuel
- 4E: Specific fault in that system
Frequently asked questions
Can I keep driving with code P014E?
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 P014E?
The most common causes are: upstream oxygen sensor aged or poisoned (silicone, oil, coolant, soot); exhaust leak ahead of the sensor (manifold, flange); mixture fault: intake air leak, injectors, fuel pressure, air flow sensor.
Related codes
- P014FO2 Sensor Slow Response - Lean to Rich Bank 2 Sensor 1
- P015CO2 Sensor Delayed Response - Rich to Lean Bank 2 Sensor 1
- P014CO2 Sensor Slow Response - Rich to Lean Bank 1 Sensor 1
- P0153O2 Sensor Circuit Slow Response Bank 2 Sensor 1
- P2A03O2 Sensor Circuit Range/Performance Bank 2 Sensor 1
- P0151O2 Sensor Circuit Low Voltage Bank 2 Sensor 1
Sources
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.