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 » U0687

Code U0687

Symptoms

• Check engine light is on

• Difficulty starting the engine

• Engine runs rough

Common Causes

• Faulty Glow Plug Control Module

• Damaged wiring or connectors

• Faulty ECU

Glossary

ECU: Engine Control Unit, the main computer in a vehicle that controls engine functions.

Glow Plug: A device used to heat the air in a diesel engine to aid in starting.

Related Codes

• U0100

• U029D

Laymans terms

This code means that a part of the car's computer system isn't talking to another part like it's supposed to. It's like when two friends stop talking to each other, and they can't work together to play a game.

Explanation

The code U0687 indicates a loss of communication with the Glow Plug Control Module.

Technical description

U0687 is a communication error code that signifies the vehicle's main computer (ECU) is unable to communicate with the Glow Plug Control Module. This can be due to a malfunction in the module itself, wiring issues, or a problem with the ECU.

Diagnosis steps

• Check for other related codes

• Inspect wiring and connectors to the Glow Plug Control Module

• Test the Glow Plug Control Module for proper operation

Repair procedures

• Repair or replace damaged wiring

• Replace the Glow Plug Control Module

• Reprogram or replace the ECU if necessary

Tools required

• OBD-II scanner

• Multimeter

• Wiring diagram

Estimated repair cost

$100 - $500

Difficulty level

Moderate

Commonly affected vehicles

• Ford F-250

• Chevrolet Silverado

• Dodge Ram

Preventive measures

• Regular maintenance checks

• Ensure wiring is secure and undamaged

• Update vehicle software as recommended

Error code type

Communication Error

User experience recommendations

• Do not ignore the check engine light

• Consult a professional mechanic for diagnosis

• Avoid DIY repairs unless experienced

Warranty information

Check with the vehicle manufacturer for warranty coverage on electronic components.

Historical data

This code has been more prevalent in diesel vehicles with advanced glow plug systems.

Urgency level

Moderate – It should be addressed soon to avoid potential starting issues.

Legal and safety notice

Driving with unresolved communication issues can lead to further vehicle damage or safety concerns.

Testing conditions

• Vehicle at operating temperature

• Key in the ON position without starting the engine

Component location

The Glow Plug Control Module is typically located near the engine, often mounted on the firewall or engine block.

FAQs

Q: Can I drive my car with code U0687?
A: It's not recommended to drive for long periods with this code, as it may lead to starting issues or further damage.

Q: How do I reset the U0687 code?
A: You can reset the code with an OBD-II scanner, but it's important to fix the underlying issue first.

Last updated: Jan 15, 2026 • Source: internal database

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