U0099

The U0099 diagnostic trouble code indicates lost communication with ultrasonic sensor module. This means one or more control modules on the vehicle's communication network are unable to exchange data properly. Network communication faults can affect multiple vehicle systems simultaneously and may cause various warning lights, reduced functionality, or driveability issues depending on which modules are affected. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: ABS/traction control warning lights on. Loss of power steering assist. Vehicle enters limp mode with reduced power. Infotainment system unresponsive. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Faulty CAN bus wiring (open, short, or damaged). Poor ground connection at module. Corroded or loose module connector pins. Aftermarket device interfering with CAN bus. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Connect an OBD-II scanner and read all stored trouble codes across all modules. Check for multiple U-codes which indicate a bus-level problem vs single module failure. Inspect battery voltage and charging system (12.4V+ engine off, 13.5-14.5V running). Inspect the CAN bus wiring for damage, chafing, or exposed conductors. Check the affected module connector for corrosion, bent pins, or water intrusion. Verify module power and ground circuits with a multimeter. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Network (U) collection on OBD Codes. We provide comprehensive, up-to-date information to help you find solutions quickly.