AutoFixDB - Free OBD-II diagnostic trouble code lookup. Find causes, symptoms, diagnostic steps and repair solutions.

Overview

P0151 indicates a low voltage condition detected from the oxygen (O2) sensor circuit at Bank 2 Sensor 1, typically affecting emissions control and fuel trim adjustments due to poor sensor signal or wiring issues

Common Symptoms

Check Engine Light (MIL) illuminated
Reduced fuel economy
Rough or unstable idle
Increased emissions

Most Common Causes

Faulty oxygen (O2) sensor (Bank 2, Sensor 1) high

Sensor may degrade or fail, causing low voltage output

Damaged wiring or connector issues to the O2 sensor high

Corrosion, chafed wires, or loose connections can lower voltage signal

Exhaust leak upstream of the sensor medium

Air intrusion can affect oxygen readings leading to low voltage signal

PCM input circuit fault low

Rare, but internal PCM circuitry failure may report incorrect sensor data

Diagnostic Steps

Use an OBD-II scan tool to confirm P0151 and any related codes

Expected: P0151 stored in memory, other codes may accompany it

Interpretation: Validates initial fault and contextual codes
Visually inspect the Bank 2, Sensor 1 O2 sensor wiring and connectors

Expected: No frayed wires, corrosion, or disconnected harness

Interpretation: Damage here can cause low voltage readings
Monitor live data with scan tool for O2 sensor voltage

Expected: Normal O2 voltage swings ~0.1-0.9V; low indicates sensor or circuit fault

Interpretation: Low steady voltage supports P0151 cause
Check for exhaust leaks upstream of the sensor (smoke/visual)

Expected: No detectable leaks near manifold or sensor

Interpretation: Leaks can skew readings causing low voltage
If sensor and wiring OK, test PCM input for proper voltage/ground

Expected: Correct reference grounds and signal voltages

Interpretation: Abnormal readings may indicate PCM or internal circuit fault

Repair Solutions

Replace faulty oxygen (O2) sensor Bank 2, Sensor 1 medium

Estimated Cost: $100 - $300

OEM-spec sensor recommended

Repair wiring/connectors to the sensor medium

Estimated Cost: $50 - $150

Includes cleaning terminals and repairing chafed wires

Fix any exhaust leaks upstream of sensor medium

Estimated Cost: $100 - $500

Costs vary by vehicle and location of leak

Replace PCM if internal circuitry fault is confirmed hard

Estimated Cost: $800 - $1500

Rare and should be confirmed by advanced diagnostics

Common Misdiagnoses

Avoid these common diagnostic mistakes:

Replacing the O2 sensor without verifying wiring or exhaust leaks first

Frequently Asked Questions

Technical definition of P0151 OBD-II Code

Technically, the P0151 code represents O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1). It usually points to a fault within the Exhaust.

Reflecting on severity: How bad is P0151?

This is a medium priority issue. Check Engine Light illuminated and potential reduced fuel economy or rough idle, but vehicle generally remains drivable

Symptoms associated with DTC P0151

The most typical signs are: Check Engine Light (MIL) illuminated, Reduced fuel economy, Rough or unstable idle.

Why is my car throwing a P0151 code?

Potential culprits include: Faulty oxygen (O2) sensor (Bank 2, Sensor 1), Damaged wiring or connector issues to the O2 sensor, Exhaust leak upstream of the sensor. A proper diagnosis is recommended.

What is the price difference for fixing P0151?

It depends on what needs to be fixed. Repair wiring/connectors to the sensor repairs are cheaper (~$150), while Replace PCM if internal circuitry fault is confirmed repairs are on the higher end (~$1500).

Is the P0151 code specific to Ford?

Yes, P0151 is a generic code that applies to all OBD-II compliant vehicles, including Ford, Toyota, Honda, Chevrolet, Nissan, Dodge, BMW, and more.

P0151: O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)