AutoCodes – Ford – P1157 1999 Ford F150

P1157 1999 Ford F150 Code - Lack Of Heated Oxygen Sensor Switches Bank 2 Sensor 2 Indicates Lean

Quick Answer

The Heated Oxygen Sensor 2 (HO2S2) (Downstream), after the three-way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Exhaust gas leaks, Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 2, Heated Oxygen Sensor 2 Bank 2 harness is open or shorted. 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: P1157 1999 Ford F150 indicates Lack Of Heated Oxygen Sensor Switches Bank 2 Sensor 2 Indicates Lean.
Common causes: Common causes include Exhaust gas leaks, Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 2, Heated Oxygen Sensor 2 Bank 2 harness is open or shorted.
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.

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Code Popularity 3,972

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 24, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
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Code P1157 1999 Ford F150 Description

The Heated Oxygen Sensor 2 (HO2S2) (Downstream), after the three-way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air-fuel mixture (air-fuel ratio) must maintain near the ideal stoichiometric ratio. The HO2S2 output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Powertrain Control Module (PCM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S2 generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The PCM interprets Lean when the HO2S2 voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The PCM interprets Rich when the HO2S2 voltage is above 0.45 V. The P1157 code will set when the PCM detects that the HO2S2 signal is below the voltage of range for an extended period.

OBDII Code P1157 1999 Ford F150 - Lack Of Heated Oxygen Sensor Switches Bank 2 Sensor 2 Indicates Lean - AutoCodes.com — P1157 1999 Ford F150 Code - Lack Of Heated Oxygen Sensor Switches Bank 2 Sensor 2 Indicates Lean

What does this mean?

What are the Possible Causes of the DTC P1157 1999 Ford F150?

Exhaust gas leaks
Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 2
Heated Oxygen Sensor 2 Bank 2 harness is open or shorted
Heated Oxygen Sensor 2 Bank 2 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors

How to Fix the DTC P1157 1999 Ford F150?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1157 1999 Ford F150 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P1157 1999 Ford F150 code?

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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.

Frequently Asked Questions about P1157 1999 Ford F150 Code

1. What does the OBDII code P1157 mean on a 1999 Ford F150?

P1157 indicates that the heated oxygen sensor (HO2S) on Bank 2 Sensor 2 is not switching properly and is reporting a lean condition.

2. What are the symptoms of the P1157 code in a 1999 Ford F150?

Common symptoms include poor fuel economy, rough idling, hesitation during acceleration, and the Check Engine Light being illuminated.

3. What causes the P1157 code to appear on a 1999 Ford F150?

Possible causes include a faulty oxygen sensor, exhaust leaks, vacuum leaks, clogged fuel injectors, or fuel delivery issues like a weak fuel pump.

4. Which sensor is affected by the P1157 code on a 1999 Ford F150?

The code refers to the downstream oxygen sensor on Bank 2 (the side of the engine opposite Cylinder 1).

5. Can a dirty or faulty mass airflow (MAF) sensor trigger the P1157 code?

Yes, a dirty or faulty MAF sensor can cause an incorrect air/fuel mixture, leading to a lean condition and triggering the P1157 code.

6. How can I diagnose the P1157 code on my 1999 Ford F150?

Start by inspecting the downstream oxygen sensor and its wiring. Check for exhaust leaks, vacuum leaks, or fuel system issues. Use a scan tool to monitor live data from the oxygen sensor.

7. Can I still drive my 1999 Ford F150 with the P1157 code?

While it may be drivable, driving with this code can lead to reduced fuel efficiency, poor performance, and potential damage to the catalytic converter if left unresolved.

8. How do I fix the P1157 code on a 1999 Ford F150?

Repairs might include replacing the oxygen sensor, fixing exhaust or vacuum leaks, cleaning the MAF sensor, or addressing fuel delivery problems.

9. How much does it cost to repair the P1157 code on a 1999 Ford F150?

Replacing the oxygen sensor typically costs between $100 and $300, including parts and labor. Additional repairs, such as fixing leaks or addressing fuel system issues, may increase the cost.

10. Can a bad catalytic converter cause the P1157 code?

Yes, a failing catalytic converter can affect downstream oxygen sensor readings, potentially triggering the P1157 code.