AutoCodes – GMC – U18AB GMC

U18AB GMC Code - Transmission Range Control Module Lost Communication With Chassis Control Module On High Speed CAN Bus

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Chassis Control Module, Chassis Control Module harness is open or shorted, Chassis Control Module circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: U18AB GMC indicates Transmission Range Control Module Lost Communication With Chassis Control Module On High Speed CAN Bus.
Common causes: Common causes include Faulty Chassis Control Module, Chassis Control Module harness is open or shorted, Chassis Control Module circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 451

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U18AB GMC Description

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the devices. The devices have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver device as an availability indication of the transmitter device. Each message contains the identification number of the transmitter device. The Diagnostic Trouble Code (DTC) will set a supervised periodic message that includes the transmitter device availability that has not been received.

OBDII Code U18AB GMC - Transmission Range Control Module Lost Communication With Chassis Control Module On High Speed CAN Bus - AutoCodes.com — U18AB GMC Code - Transmission Range Control Module Lost Communication With Chassis Control Module On High Speed CAN Bus

What does this mean?

What are the Possible Causes of the DTC U18AB GMC?

Faulty Chassis Control Module
Chassis Control Module harness is open or shorted
Chassis Control Module circuit poor electrical connection

How to Fix the DTC U18AB GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U18AB GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the U18AB GMC code?

Need more information on how to fix the U18AB GMC code? Get Access to Factory Service Manuals

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about U18AB GMC Code

1. What are the common symptoms of OBDII code U18AB in a GMC vehicle?

The common symptoms include transmission shifting issues, the transmission stuck in one gear, illumination of the Check Engine Light, and potential loss of communication with other control modules.

2. What does the OBDII code U18AB GMC indicate?

This code indicates that the Transmission Range Control Module has lost communication with the Chassis Control Module on the High-Speed CAN Bus network.

3. What are some possible causes of the U18AB code in a GMC vehicle?

Possible causes include a faulty Transmission Range Control Module, issues with the Chassis Control Module, damaged wiring or connectors in the CAN Bus network, or a communication error between modules.

4. How can I diagnose the U18AB code in my GMC vehicle?

Diagnosing this code typically involves using a professional OBDII scanner to retrieve the code, checking for other related codes, inspecting the wiring and connectors in the CAN Bus network, and testing the communication between modules.

5. Can I still drive my GMC vehicle with the U18AB code present?

It is not recommended to drive the vehicle with the U18AB code present, as it can lead to potential transmission issues and affect the overall performance and safety of the vehicle.

6. How is the U18AB code typically repaired in a GMC vehicle?

Repairing this code usually involves addressing the root cause of the communication error, such as replacing the faulty module, repairing damaged wiring or connectors, or reprogramming the control modules as needed.

7. Is it possible to reset the U18AB code without fixing the underlying issue?

Resetting the code without addressing the underlying issue may temporarily turn off the Check Engine Light, but the problem will likely reoccur until the root cause is properly repaired.

8. Can a DIY enthusiast fix the U18AB code in a GMC vehicle?

While basic troubleshooting like checking for loose connections or damaged wires can be done by a DIY enthusiast, diagnosing and repairing the specific cause of the U18AB code may require professional tools and expertise.

9. How long does it typically take to repair the U18AB code in a GMC vehicle?

The repair time can vary depending on the exact cause of the code and the complexity of the repair needed. It is best to consult with a mechanic for a more accurate estimate of the repair time.

10. How can I prevent the U18AB code from occurring in the future?

Regular maintenance checks, ensuring proper wiring connections, and addressing any communication issues between control modules promptly can help prevent the recurrence of the U18AB code in your GMC vehicle.