AutoCodes – Honda – P0138 1999 Honda Civic

P0138 1999 Honda Civic Code - HO2S Bank 1 Sensor 2 Circuit Low Voltage

Quick Answer

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0138 1999 Honda Civic indicates HO2S Bank 1 Sensor 2 Circuit Low Voltage.
Common causes: Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 7,083

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 31, 2024

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0138 1999 Honda Civic Description

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after 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 be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S 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 ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

OBDII Code P0138 1999 Honda Civic - HO2S Bank 1 Sensor 2 Circuit Low Voltage - AutoCodes.com — P0138 1999 Honda Civic Code - HO2S Bank 1 Sensor 2 Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 1999 Honda Civic?

Faulty Rear Heated Oxygen Sensor Bank 1
Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Intake air leaks
Exhaust gas leaks
Inappropriate fuel pressure
Faulty fuel injectors

How to Fix the DTC P0138 1999 Honda Civic?

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 does this mean?

Code Tech Notes

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0138 1999 Honda Civic 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 P0138 1999 Honda Civic code?

Need more information on how to fix the P0138 1999 Honda Civic code? Get Access to Factory Service Manuals

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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 P0138 1999 Honda Civic Code

1. What does OBDII code P0138 on my 1999 Honda Civic mean?

This code indicates a problem with the HO2S (Heated Oxygen Sensor) Bank 1 Sensor 2 circuit, specifically low voltage detected.

2. What are the common symptoms of HO2S Bank 1 Sensor 2 Circuit Low Voltage issue?

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

3. What are the possible causes of the P0138 code on a 1999 Honda Civic?

Potential causes include a faulty oxygen sensor, wiring issues in the sensor circuit, exhaust leaks, engine misfires, or a malfunctioning catalytic converter.

4. How can I diagnose the HO2S Bank 1 Sensor 2 Circuit Low Voltage problem on my Honda Civic?

Diagnosis typically involves inspecting the oxygen sensor and its wiring for damage, checking for exhaust leaks, testing the sensor's voltage output, and scanning for other related trouble codes.

5. Can I drive my 1999 Honda Civic with the P0138 code?

It is not recommended to drive for an extended period with this code, as it can negatively affect engine performance and emissions. Seek a professional diagnosis and repair as soon as possible.

6. How do I repair the HO2S Bank 1 Sensor 2 Circuit Low Voltage issue on my Honda Civic?

Repair options may include replacing the oxygen sensor, repairing damaged wiring, fixing exhaust leaks, addressing engine misfires, or replacing a faulty catalytic converter.

7. Is it possible to clear the P0138 code on a 1999 Honda Civic without fixing the issue?

Clearing the code without addressing the underlying problem will only temporarily turn off the Check Engine Light. The issue will persist and may lead to further complications.

8. Can a dirty MAF sensor cause the P0138 code on a 1999 Honda Civic?

While a dirty MAF sensor can impact engine performance, it is not a common cause of the P0138 code specifically. Focus on diagnosing the oxygen sensor circuit and related components.

9. Will the P0138 code on my 1999 Honda Civic cause a vehicle to fail emissions tests?

Yes, a vehicle with the P0138 code may fail emissions tests due to increased emissions and poor overall performance. It is advisable to address the issue before undergoing an emissions test.

10. How much does it typically cost to repair the HO2S Bank 1 Sensor 2 Circuit Low Voltage issue on a 1999 Honda Civic?

The cost of repairs can vary depending on the exact cause of the problem and the required parts and labor. On average, expect to pay between $100 to $300 for parts and labor.