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 » U0665

Code U0665

Symptoms

• Check engine light on

• Vehicle may not start

• Loss of certain vehicle functions

Common Causes

• Faulty control module

• Damaged wiring or connectors

• Network communication issues

Glossary

CAN: Controller Area Network, a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other.

DTC: Diagnostic Trouble Code, a code that indicates a problem with the vehicle.

Related Codes

• U0100

• U0140

Laymans terms

This code means that one of the car's computers isn't talking to another computer like it should. Imagine if two friends were playing a game and one stopped responding.

Explanation

The U0665 code indicates a communication problem between the vehicle's control modules.

Technical description

U0665 is a diagnostic trouble code (DTC) indicating a communication error on the vehicle's Controller Area Network (CAN) bus. This error occurs when a specific module fails to communicate with other modules on the network.

Diagnosis steps

• Check for other related codes

• Inspect wiring and connectors

• Test the functionality of the control module

Repair procedures

• Repair or replace damaged wiring

• Replace faulty control module

• Clear the codes and test drive

Tools required

• OBD-II scanner

• Multimeter

• Wiring diagram

Estimated repair cost

$150 - $500

Difficulty level

Moderate

Commonly affected vehicles

• Ford F-150

• Chevrolet Silverado

• Toyota Camry

Preventive measures

• Regular maintenance checks

• Ensure connectors are secure

• Avoid water exposure to electronic components

Error code type

Communication Error

User experience recommendations

• Ensure vehicle software is up to date

• Have a professional diagnose the issue

Warranty information

Check with the manufacturer for warranty coverage on electronic components.

Historical data

This code has been more prevalent as vehicles have become more reliant on networked control modules.

Urgency level

Moderate – It should be addressed soon to avoid further issues.

Legal and safety notice

Ignoring communication errors can lead to safety issues if critical systems are affected.

Testing conditions

• Vehicle ignition on

• Access to diagnostic tools

Component location

The affected control module is typically located in the engine bay or under the dashboard.

FAQs

Q: Can I drive my car with a U0665 code?
A: It's not recommended as it may affect vehicle performance and safety.

Q: Will a U0665 code clear itself?
A: No, the issue needs to be fixed and the code cleared with a scanner.

Last updated: Oct 29, 2025 • Source: internal database

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