How to Diagnose and Fix P0138 Code in Chevy Silverado

AvatarByCarl Frisch

The P0138 code indicates that the Chevy Silverado’s oxygen sensor voltage has remained above a predetermined level for too long. The oxygen sensor is responsible for monitoring the air-to-fuel ratio in the engine, and when it detects a lean condition (too much air, not enough fuel), it sends a signal to the vehicle’s powertrain control module (PCM) to adjust the fuel delivery accordingly. If this signal remains active for too long, it triggers a P0138 code.

Common causes of a P0138 code include:
•A faulty oxygen sensor
•A vacuum leak in the intake manifold or other engine components
•A malfunctioning PCM or wiring issue
•An incorrect air-fuel mixture
•A problem with fuel injectors
•Dirty air filter or clogged exhaust system
•Contaminated fuel

To diagnose and repair this issue, a qualified technician will use an OBD-II scanner to read and analyze any stored trouble codes. They may also use an oscilloscope to check the waveform of the oxygen sensor signal and make sure it is within factory specifications. They may also inspect all related wiring and connections, as well as check relevant components such as fuel injectors and vacuum lines. Finally, they may also perform an emissions test to make sure that everything is functioning properly.

Automobile: P0138 Code in Chevy Silverado

The P0138 code is a diagnostic trouble code (DTC) for an oxygen sensor circuit high voltage on the Chevy Silverado. It’s important to know the symptoms, causes and diagnosis of this code in order to properly repair your vehicle.

Symptoms of P0138 Code

The main symptom associated with a P0138 code is the illumination of the engine light. This can be accompanied by the check engine light code being displayed on the dashboard and a noticeable reduction in engine performance. The cause of this issue must be addressed in order to ensure proper functioning of the vehicle.

Causes of P0138 Code

There are several potential causes for this DTC including an oxygen sensor voltage that is too high, wiring issues or corroded connectors, and a faulty oxygen sensor or PCM/ECM. It’s important to inspect all possible causes before attempting any repairs.

Diagnosis of P0138 Code in Chevy Silverado

Before beginning any repairs, it’s important to perform a pre-inspection step for diagnosis. This includes checking for technical service bulletins (TSB) as well as scanning the vehicle computer for codes and freeze frame data. Once this is done, testing steps should be taken to diagnose the source of the issue. Testing should include checking the heated oxygen sensor (HO2S) voltage output as well as testing the O2 sensor heater circuit resistance and voltage supply.

Repair Options for P0138 Code in Chevy Silverado

Once you have accurately diagnosed your vehicle’s issue, you can begin considering repair options. In most cases, this will involve replacing the oxygen sensor (HO2S). Make sure that you use only genuine OEM parts when replacing any components on your vehicle to ensure proper functioning and maximum longevity.

Repair Process for P0138 Code Chevy Silverado

Replacing the Oxygen Sensor (HO2S) is the first step of repair process for P0138 Code Chevy Silverado. It is necessary to inspect the wiring and connectors to ensure that they are connected properly. After replacing the HO2S, it is important to reset the Powertrain Control Module/Engine Control Module (PCM/ECM) and clear any trouble codes from memory.

Common Issues with P0138 Code in Chevy Silverado

When P0138 code appears in Chevy Silverado, there will be a decrease in vehicle performance such as poor acceleration and hesitation when accelerating. High fuel consumption and excessive exhaust emissions are also common issues that can arise with this code.

Preventive Maintenance to Avoid P0138 Code in Chevy Silverado

To prevent this code from appearing, it is important to regularly inspect the Oxygen Sensors (HO2S). This includes checking for any signs of corrosion or damage, ensuring that all wiring and connectors are securely attached, and ensuring that all sensors are functioning correctly. Taking these preventive measures can help avoid any unnecessary repairs or further damage to your vehicle’s systems.

FAQ & Answers

Q: What is P0138 Code?
A: P0138 Code is an engine diagnostic trouble code that indicates the oxygen sensor voltage output from the oxygen sensor is too high.

Q: What are the symptoms of P0138 Code in a Chevy Silverado?
A: The symptoms of P0138 Code in a Chevy Silverado include engine light illumination, check engine light code displayed, and vehicle not running properly.

Q: What are the common causes of P0138 Code?
A: The common causes of P0138 Code include O2 Sensor Voltage Too High, Wiring Issue or Corroded Connectors, and Faulty O2 Sensor or PCM/ECM.

Q: What are the common issues with P0138 Code in a Chevy Silverado?
A: The common issues with P0138 Code in a Chevy Silverado include poor acceleration, hesitation when accelerating, high fuel consumption, and excessive exhaust emissions.

Q: What preventive maintenance should be done to avoid P0138 Code in a Chevy Silverado?
A: Preventive maintenance to avoid P0138 Code in a Chevy Silverado should include regular inspection of oxygen sensors (HO2S).

In conclusion, a P0138 code on a Chevy Silverado can be caused by several issues. Although the most common cause is an oxygen sensor circuit malfunction, other potential causes include a faulty wiring harness or ECM. It is important to properly diagnose the issue before attempting any repairs to ensure that the problem is properly addressed in order to prevent any additional issues from occurring.

Author Profile

Carl Frisch
Carl Frisch
With more than 30 years in the bicycle industry, I have a strong background in bicycle retailing, sales, marketing and customer service. I have a passion for cycling and a dedication to excellence. As a manager, I worked diligently to increase my capabilities and responsibilities, managing up to eleven mechanics (at Palo Alto Bicycles) and later as a working partner in my own store.

As the shop owner of Spoke n’ Word Cycles in Socorro, NM, the success of the mission was my responsibility, which I pursued passionately since we opened in 2003 through the spring of 2011. I am adept at managing owned and loan inventory, preparing weekly & annual inventory statements, and managing staff. The role as managing partner also allowed me tremendous freedom. I used this personal freedom to become more deeply involved in my own advancement as a mechanic, to spearhead local trail building, and advocating for cycling both locally and regionally.

As a mechanic, I have several years doing neutral support, experience as a team mechanic, and experience supporting local rides, races, club events. I consistently strive to ensure that bicycles function flawlessly by foreseeing issues and working with the riders, soigners, coaches and other mechanics. Even with decades of experience as a shop mechanic and team mechanic, and continue to pursue greater involvement in this sport as a US Pro Mechanic, and UCI Pro Mechanic.

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