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Engine-Codes – Mercury – P1151 Mercury

P1151 Mercury Code - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2

Quick Answer

The P1151 code for Mercury vehicles indicates a lack of upstream heated oxygen sensor switch sensor that indicates a lean condition in bank 2. Common causes include Faulty upstream oxygen sensor, Vacuum leak in the intake system, Clogged fuel injector. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P1151 Mercury indicates Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2.
Common causes
Common causes include Faulty upstream oxygen sensor, Vacuum leak in the intake system, Clogged fuel injector.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 10, 2024
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Code P1151 Mercury Description

The P1151 code for Mercury vehicles indicates a lack of upstream heated oxygen sensor switch sensor that indicates a lean condition in bank 2. The upstream oxygen sensor is responsible for measuring the oxygen content in the exhaust gases before they enter the catalytic converter. This information is crucial for the engine control module (ECM) to adjust the air-fuel mixture for optimal combustion. When the sensor indicates a lean condition in bank 2, it means that there is an imbalance in the air-fuel ratio, with too much air and not enough fuel entering the engine.

OBDII Code P1151 Mercury - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2
P1151 Mercury Code - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2

Common Causes of P1151 Mercury

  1. Faulty upstream oxygen sensor
  2. Vacuum leak in the intake system
  3. Clogged fuel injector
  4. Malfunctioning fuel pressure regulator
  5. Problem with the mass airflow sensor

Symptoms of P1151 Mercury

  1. Rough idle or stalling
  2. Hesitation or lack of power during acceleration
  3. Poor fuel economy
  4. Check Engine Light illuminated
  5. Increased emissions

How to Fix P1151 Mercury

  1. Diagnose the issue by retrieving the P1151 code and performing a thorough inspection of the upstream oxygen sensor, intake system, fuel injectors, fuel pressure regulator, and mass airflow sensor.
  2. Replace the faulty upstream oxygen sensor if it is determined to be the cause of the lean condition in bank 2.
  3. Repair any vacuum leaks in the intake system and ensure all connections are secure.
  4. Clean or replace clogged fuel injectors and test the fuel pressure regulator for proper operation.
  5. Inspect the mass airflow sensor for any dirt or debris that could affect its performance and clean or replace it if necessary.

Cost to Fix P1151 Mercury

The typical repair costs for addressing a P1151 code on a Mercury vehicle can vary depending on the specific cause of the issue. Replacing a faulty upstream oxygen sensor can range from $100 to $300, while diagnosing and repairing vacuum leaks, fuel injectors, fuel pressure regulator, or mass airflow sensor can each cost between $100 to $500. Overall, the total repair cost for resolving a P1151 code may range from $200 to $1500, including parts and labor. It's important to note that diagnosis time and labor rates at auto repair shops can vary, so it's recommended to check local rates for a more accurate estimate.

What does this mean?

Tech Notes for P1151 Mercury

The code means that the Powertrain Control Module (PCM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.











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When is the Code Detected?

When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

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