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 » U0635

Code U0635

Symptoms

• Check engine light on

• Vehicle systems not functioning properly

• Intermittent electrical issues

Common Causes

• Faulty control module

• Damaged wiring or connectors

• Network communication interruption

Glossary

CAN bus: Controller Area Network bus, a vehicle's internal communication network.

Control module: An electronic component that controls various vehicle functions.

Related Codes

• U0100

• U0121

Laymans terms

This code means that one of the computers in the car is having trouble talking to another computer. It's like when your phone can't connect to Wi-Fi.

Explanation

U0635 indicates a communication error between control modules in the vehicle.

Technical description

The U0635 code is a network communication fault code that indicates a lost communication with a specific control module on the vehicle's CAN bus network. This can occur due to wiring issues, module failures, or network interruptions.

Diagnosis steps

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

• Inspect wiring and connectors for damage.

• Test the suspected control module for faults.

Repair procedures

• Repair or replace damaged wiring.

• Replace faulty control module.

• Clear the code and test drive the vehicle.

Tools required

• OBD-II scanner

• Multimeter

• Screwdriver set

Estimated repair cost

$100 - $500

Difficulty level

Moderate

Commonly affected vehicles

• Ford F-150

• Chevrolet Silverado

• Toyota Camry

Preventive measures

• Regularly inspect vehicle wiring.

• Avoid moisture exposure to electrical components.

• Ensure all connectors are securely fastened.

Error code type

Network Communication Issue

User experience recommendations

• Have the vehicle inspected by a professional.

• Do not ignore the check engine light.

• Regular maintenance can prevent such issues.

Warranty information

Check with the vehicle manufacturer for warranty coverage on control modules.

Historical data

U0635 is a relatively uncommon code that typically appears in vehicles with complex electronic systems.

Urgency level

Moderate – Addressing this issue promptly can prevent further vehicle system malfunctions.

Legal and safety notice

Ignoring this code can lead to vehicle safety systems not functioning properly.

Testing conditions

• Vehicle must be running.

• All electrical systems should be operational.

Component location

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

FAQs

Q: Can I drive with a U0635 code?
A: It's not recommended, as it may affect vehicle performance and safety systems.

Q: Will disconnecting the battery clear the code?
A: Disconnecting the battery may temporarily clear the code, but it won't fix the underlying issue.

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

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