AutoCodes – Honda – P0138 1998 Honda Civic

P0138 1998 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 1998 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 11,672

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 1998 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 1998 Honda Civic - HO2S Bank 1 Sensor 2 Circuit Low Voltage - AutoCodes.com — P0138 1998 Honda Civic Code - HO2S Bank 1 Sensor 2 Circuit Low Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 1998 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 1998 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 1998 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 1998 Honda Civic 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 P0138 1998 Honda Civic Code

1. What are common symptoms of OBDII code P0138 in a 1998 Honda Civic?

- Common symptoms include poor fuel economy, rough idle, and the illumination of the check engine light.

2. What does the OBDII code P0138 in a 1998 Honda Civic indicate?

- The code P0138 indicates that the HO2S (Heated Oxygen Sensor) Bank 1 Sensor 2 circuit is experiencing low voltage.

3. What are the possible causes of OBDII code P0138 in a 1998 Honda Civic?

- Possible causes include a faulty oxygen sensor, wiring issues, exhaust leaks, or an engine misfire.

4. How can I diagnose the HO2S Bank 1 Sensor 2 circuit in a 1998 Honda Civic?

- Diagnose the circuit by checking the sensor's wiring, connectors, and resistance, as well as inspecting for any exhaust leaks.

5. Can a dirty or contaminated oxygen sensor cause code P0138 in a 1998 Honda Civic?

- Yes, a dirty or contaminated oxygen sensor can lead to false readings and trigger the P0138 code.

6. What is the recommended repair for OBDII code P0138 in a 1998 Honda Civic?

- The recommended repair is to replace the HO2S Bank 1 Sensor 2 if it is faulty, repair any wiring issues, and clear the error code.

7. How crucial is it to address OBDII code P0138 promptly in a 1998 Honda Civic?

- It is important to address the code promptly to prevent potential damage to the catalytic converter and ensure optimal engine performance.

8. Can I drive my 1998 Honda Civic with an unresolved P0138 code?

- It is not recommended to drive the vehicle with an unresolved P0138 code as it can lead to decreased fuel efficiency and engine performance.

9. Is it possible for a loose gas cap to trigger code P0138 in a 1998 Honda Civic?

- While a loose gas cap can trigger other codes related to the EVAP system, it is unlikely to directly cause the P0138 code.

10. How can I prevent OBDII code P0138 from recurring in my 1998 Honda Civic?

- Regularly maintaining your vehicle, ensuring proper installation of components, and addressing any underlying issues promptly can help prevent the recurrence of the P0138 code.