P0031: Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 1

What does P0031 mean?

P0031 is a diagnostic trouble code indicating "Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 1". The ECU is detecting a voltage reading that is below the expected range in the o2 sensors circuit. This typically points to a wiring short, a faulty sensor, or a grounding issue.

Symptoms you may notice

• Check engine light (MIL) illuminated on dashboard
• Decreased fuel efficiency
• Rough or irregular idle
• Engine running rough
• Intermittent warning lights

Common causes

• Damaged or corroded wiring harness
• Loose or disconnected electrical connector
• Failed o2 sensors sensor or actuator
• Blown fuse in the related circuit
• Poor ground connection

What should you do?

This code sits in an engine peripheral, typically emissions or forced induction. It will not take braking or steering away, but it can put the car into limp mode, cost you fuel and fail a roadworthy. Book it in rather than clearing it and hoping.