AutoCodes – Cadillac – P0139 Cadillac

P0139 Cadillac Code - HO2S Slow Response Bank 1 Sensor 2

Quick Answer

The Powertrain Control Module (PCM) provides a .45 volt reference signal to the Heated Oxygen Sensor (HO2S) through the Bank 1 high signal circuit. Common causes include Faulty Heated Oxygen Sensor (HO2S) Bank 1 Sensor 2, HO2S Bank 1 Sensor 2 harness is open or shorted, HO2S Bank 1 Sensor 2circuit poor electrical connection. 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: P0139 Cadillac indicates HO2S Slow Response Bank 1 Sensor 2.
Common causes: Common causes include Faulty Heated Oxygen Sensor (HO2S) Bank 1 Sensor 2, HO2S Bank 1 Sensor 2 harness is open or shorted, HO2S Bank 1 Sensor 2circuit poor electrical connection.
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 865

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Mar 14, 2021

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Cost to Diagnose
FAQs
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Code P0139 Cadillac Description

The Powertrain Control Module (PCM) provides a .45 volt reference signal to the Heated Oxygen Sensor (HO2S) through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in an open loop. When HO2S is warm, sensor voltage will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture. If the oxygen sensor is slow to respond to changes in exhaust oxygen content, the Diagnostic Trouble Code (DTC) will set.

OBDII Code P0139 Cadillac - HO2S Slow Response Bank 1 Sensor 2 - AutoCodes.com — P0139 Cadillac Code - HO2S Slow Response Bank 1 Sensor 2

What does this mean?

What are the Possible Causes of the DTC P0139 Cadillac?

Faulty Heated Oxygen Sensor (HO2S) Bank 1 Sensor 2
HO2S Bank 1 Sensor 2 harness is open or shorted
HO2S Bank 1 Sensor 2circuit poor electrical connection

How to Fix the DTC P0139 Cadillac?

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 P0139 Cadillac 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.

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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 P0139 Cadillac Code

1. What are the common symptoms of OBDII code P0139 in a Cadillac?

- Common symptoms include poor fuel economy, rough idling, engine misfires, and the illumination of the Check Engine Light.

2. What does the OBDII code P0139 "HO2S Slow Response Bank 1 Sensor 2" mean for a Cadillac?

- This code indicates that the downstream oxygen sensor on bank 1 is not responding quickly enough to changes in the air-fuel ratio.

3. What are the possible causes of OBDII code P0139 in a Cadillac?

- Common causes include a faulty oxygen sensor, wiring issues, exhaust leaks, engine misfires, or a problem with the engine's air-fuel mixture.

4. How can I diagnose the OBDII code P0139 in my Cadillac?

- Diagnosing this code typically involves checking the oxygen sensor's wiring, testing the sensor's response, inspecting for exhaust leaks, and analyzing the engine's performance data.

5. Can I still drive my Cadillac with the OBDII code P0139 present?

- While it may be possible to drive the vehicle with this code, it is not recommended as it can lead to reduced fuel efficiency and potential engine damage over time.

6. How can I repair OBDII code P0139 in my Cadillac?

- Repairs may involve replacing the downstream oxygen sensor, fixing any wiring issues, addressing exhaust leaks, resolving engine misfires, or recalibrating the air-fuel mixture.

7. Is it possible to reset the OBDII code P0139 in a Cadillac without fixing the underlying issue?

- While clearing the code may temporarily turn off the Check Engine Light, the issue will likely reappear if the root cause is not addressed.

8. Can a DIY enthusiast fix OBDII code P0139 in a Cadillac?

- Depending on the individual's skill level and access to tools, some DIY enthusiasts may be able to diagnose and replace the downstream oxygen sensor themselves to fix this code.

9. How important is it to address OBDII code P0139 promptly in a Cadillac?

- It is crucial to address this code promptly to prevent potential damage to the engine, ensure optimal fuel efficiency, and maintain the vehicle's overall performance.

10. How can regular maintenance help prevent OBDII code P0139 in a Cadillac?

- Regular maintenance, such as timely oxygen sensor replacements, checking for exhaust leaks, and addressing engine issues promptly, can help prevent the occurrence of this code in a Cadillac.