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 » C0665

Code C0665

Symptoms

• ABS warning light on

• Traction control system warning light on

• Inconsistent speedometer readings

Common Causes

• Incorrect wheel speed sensor installed

• Faulty wheel speed sensor

• Incorrect sensor calibration

Glossary

OBD-II: On-Board Diagnostics, a standardized system for vehicle diagnostics.

ABS: Anti-lock Braking System, prevents the wheels from locking up during braking.

Related Codes

• C0666

• C0667

Laymans terms

The car's computer thinks the wrong part is used for the left rear wheel sensor. It's like trying to use a puzzle piece that doesn't fit.

Explanation

The vehicle's control module detects that the left rear wheel speed sensor does not match the expected specifications, possibly due to an incorrect part being installed.

Technical description

The C0665 code indicates that the control module has identified an issue with the left rear wheel speed sensor, specifically that it may not be the correct component for the vehicle. This can affect the vehicle's stability control and anti-lock braking systems.

Diagnosis steps

• Verify the part number of the installed wheel speed sensor.

• Check for wiring issues or connection problems.

• Test the sensor signal with a diagnostic tool.

Repair procedures

• Replace the wheel speed sensor with the correct part.

• Repair or replace damaged wiring or connectors.

• Recalibrate the sensor if necessary.

Tools required

• OBD-II scanner

• Multimeter

• Wrench set

Estimated repair cost

$100 - $300

Difficulty level

Moderate

Commonly affected vehicles

• Chevrolet Silverado

• GMC Sierra

• Cadillac Escalade

Preventive measures

• Ensure correct part numbers when replacing sensors.

• Regularly inspect wiring and connectors.

• Use OEM parts for replacements.

Error code type

Sensor Issue

User experience recommendations

• Have a professional mechanic inspect the sensor.

• Avoid driving at high speeds until the issue is resolved.

Warranty information

Check with the vehicle manufacturer for warranty coverage on sensor replacements.

Historical data

This code has been commonly reported in vehicles with aftermarket sensor replacements.

Urgency level

Moderate – It should be addressed soon to ensure proper vehicle safety systems function.

Legal and safety notice

Ignoring this issue may affect vehicle safety systems like ABS and traction control.

Testing conditions

• Vehicle on a flat surface

• Ignition in the ON position

Component location

The left rear wheel speed sensor is located near the left rear wheel hub assembly.

FAQs

Q: Can I drive with a C0665 code?
A: It's not recommended as it may affect your vehicle's safety systems.

Q: How do I know if the sensor is wrong?
A: Check the part number and compare it with the manufacturer's specifications.

Last updated: Jun 8, 2026 • Source: internal database

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