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 » U0656

Code U0656

Symptoms

• Warning lights on the dashboard

• Malfunctioning electronic systems

• Intermittent vehicle performance issues

Common Causes

• Faulty control module

• Damaged wiring or connectors

• Network communication error

Glossary

Control Module: A computer that controls various functions in the vehicle.

CAN Bus: A network that allows different control modules to communicate with each other.

Related Codes

• U0100

• U0121

Laymans terms

This code means that one of the car's computers is having trouble talking to another computer. It's like when two friends are trying to talk on the phone, but the connection is bad.

Explanation

U0656 indicates a communication problem between control modules in the vehicle.

Technical description

The U0656 code is set when the vehicle's control modules, such as the Body Control Module (BCM) or Powertrain Control Module (PCM), fail to communicate properly with each other over the Controller Area Network (CAN) bus. This can be due to a loss of communication or a malfunction in the network.

Diagnosis steps

• Check for other related codes

• Inspect wiring and connectors for damage

• Test communication lines with a diagnostic tool

Repair procedures

• Repair or replace damaged wiring

• Replace faulty control module

• Update module software

Tools required

• OBD-II scanner

• Multimeter

• CAN bus diagnostic tool

Estimated repair cost

$100 - $1000

Difficulty level

Moderate

Commonly affected vehicles

• Ford F-150

• Chevrolet Silverado

• Toyota Camry

Preventive measures

• Regular vehicle maintenance

• Inspect wiring for wear

• Keep software updated

Error code type

Communication Issue

User experience recommendations

• Have a professional diagnose the issue

• Avoid DIY repairs if unfamiliar with vehicle electronics

Warranty information

Check vehicle warranty for coverage on electronic components.

Historical data

This code has been more common in vehicles with advanced electronic systems.

Urgency level

Moderate – Should be addressed soon to prevent further issues.

Legal and safety notice

Driving with unresolved communication issues can lead to safety concerns.

Testing conditions

• Vehicle at operating temperature

• All electronic systems active

Component location

Located within the vehicle's electronic control modules, often under the dashboard or in the engine bay.

FAQs

Q: Can I drive with a U0656 code?
A: It's not recommended as it may affect vehicle performance and safety systems.

Q: Does a U0656 code mean my car will stop working?
A: Not necessarily, but it can cause certain systems to malfunction.

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

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