Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's computer is saying that a part called the oxygen sensor, which checks how much oxygen is in the exhaust, is getting too much power. It's like when your flashlight is too bright because it has too many batteries.
This code indicates that the oxygen sensor located after the catalytic converter on the first bank of the engine is reporting a voltage higher than expected.
The P0138 code is triggered when the Engine Control Module (ECM) detects that the voltage signal from the oxygen sensor (O2 sensor) located on bank 1, sensor 2 is higher than the specified range. This sensor measures the amount of oxygen in the exhaust gases after they pass through the catalytic converter. A high voltage reading indicates a rich air-fuel mixture or a sensor malfunction.
• Check Engine Light is on
• Poor fuel economy
• Failed emissions test
• Faulty oxygen sensor
• Short to voltage in O2 sensor signal circuit
• Fuel pressure too high
Oxygen Sensor: A device that measures the oxygen level in the exhaust gases.
Catalytic Converter: A component that reduces harmful emissions from the exhaust.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the oxygen sensor voltage with a multimeter.
• Replace the faulty oxygen sensor.
• Repair or replace damaged wiring or connectors.
• Adjust the fuel pressure if necessary.
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $300
Moderate
• Toyota Camry
• Honda Accord
• Ford F-150
• Regular maintenance checks
• Use quality fuel
• Inspect exhaust system periodically
Sensor Issue
• Do not ignore the Check Engine Light.
• Have your vehicle inspected by a professional if unsure.
• Regularly check and maintain your vehicle's sensors.
Oxygen sensors are often covered under the vehicle's emissions warranty.
The P0138 code has been a common diagnostic trouble code since the introduction of OBD-II systems, often related to sensor wear and tear.
Moderate – It should be addressed soon to prevent potential damage to the catalytic converter and to maintain fuel efficiency.
Driving with a faulty oxygen sensor can lead to increased emissions, which may not comply with local environmental regulations.
• Engine at operating temperature
• Vehicle running at idle
The oxygen sensor for Bank 1 Sensor 2 is located in the exhaust system, downstream of the catalytic converter on the side of the engine with cylinder 1.
Q: What does the oxygen sensor do?
A: The oxygen sensor measures the amount of oxygen in the exhaust gases to help the engine control module adjust the air-fuel mixture.
Q: Can I drive with a P0138 code?
A: You can drive for a short period, but it's best to fix it soon to avoid potential damage to the catalytic converter and increased emissions.
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Universal · Digital multimeter
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Relevant when the code or supporting diagnostics point toward upstream or downstream oxygen-sensor faults.
This code family often involves upstream or downstream oxygen-sensor diagnosis.
Verify exact sensor position and vehicle fitment before buying.
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Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.