What is an OBD2 code?

An OBD2 (On-Board Diagnostics) code is a diagnostic trouble code (DTC) generated by your vehicle's computer system when it detects a problem. These codes help identify specific issues with your vehicle's engine, transmission, emissions, or other systems.

How do I read OBD2 codes?

To read OBD2 codes, you'll need an OBD2 scanner. Plug it into your vehicle's OBD2 port (usually located under the dashboard), turn your key to the 'ON' position, and follow your scanner's instructions to retrieve the codes. Each code starts with a letter (P, B, C, or U) followed by four numbers.

What do the different types of OBD2 codes mean?

OBD2 codes are categorized by their first letter: P (Powertrain) for engine and transmission issues, B (Body) for interior systems like airbags, C (Chassis) for mechanical systems like brakes, and U (Network) for computer and module communication problems.

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Home » OBD2 Codes » P0055

Code P0055

Symptoms

• Check Engine Light is on

• Poor fuel economy

• Failed emissions test

Common Causes

• Faulty oxygen sensor

• Damaged wiring or connectors

• Blown fuse for the oxygen sensor heater circuit

Glossary

HO2S: Heated Oxygen Sensor

ECM: Engine Control Module

Related Codes

• P0030

• P0050

Official description

HO2S Heater Resistance Bank 1 Sensor 3

Laymans terms

Your car has a special sensor that helps it know how much fuel to use. This sensor has a heater, and the heater isn't working right.

Explanation

The P0055 code indicates a problem with the heater circuit of the oxygen sensor located in Bank 1, Sensor 3. The resistance in the heater circuit is not within the expected range.

Technical description

The Heated Oxygen Sensor (HO2S) helps the engine control module (ECM) determine the correct air-fuel ratio for the engine. The heater in the sensor helps it reach operating temperature quickly. If the resistance in the heater circuit is not within specifications, the ECM triggers the P0055 code.

Diagnosis steps

• Use an OBD-II scanner to verify the code.

• Inspect the wiring and connectors for damage.

• Check the resistance of the oxygen sensor heater circuit.

Repair procedures

• Replace the faulty oxygen sensor.

• Repair or replace damaged wiring or connectors.

• Replace the blown fuse in the heater circuit.

Tools required

• OBD-II scanner

• Multimeter

• Basic hand tools

Estimated repair cost

$100 - $300

Difficulty level

Moderate

Commonly affected vehicles

• Toyota Camry

• Honda Accord

• Ford F-150

Preventive measures

• Regularly inspect and maintain sensor wiring.

• Perform routine vehicle diagnostics.

• Use high-quality fuel to prevent sensor contamination.

Error code type

Sensor Issue

User experience recommendations

• Address the issue promptly to avoid further damage.

• Consult a professional mechanic if unsure about repairs.

Warranty information

Check with the manufacturer for warranty coverage on emissions-related components.

Historical data

This code has been common in vehicles with aging oxygen sensors or poor maintenance history.

Urgency level

Moderate – It should be addressed soon to avoid increased emissions and fuel consumption.

Legal and safety notice

Ignoring this code may lead to failing emissions tests, which can be illegal in some regions.

Testing conditions

• Engine at operating temperature

• Vehicle in closed-loop operation

Component location

The oxygen sensor is located in the exhaust system, downstream of the catalytic converter on Bank 1.

FAQs

Q: Can I drive with a P0055 code?
A: While you can drive with this code, it's best to fix it soon to avoid poor fuel economy and emissions issues.

Q: How do I know if my oxygen sensor is bad?
A: Symptoms of a bad oxygen sensor include a check engine light, poor fuel economy, and failed emissions tests.

Last updated: Oct 6, 2025 • Source: internal database

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