AutoCodes – Chevrolet – U18AC Chevrolet

U18AC Chevrolet Code - Transmission Range Control Module Lost Communication With Chassis Control Module On Chassis Expansion 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: U18AC Chevrolet indicates Transmission Range Control Module Lost Communication With Chassis Control Module On Chassis Expansion 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 910

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 U18AC Chevrolet 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 U18AC Chevrolet - Transmission Range Control Module Lost Communication With Chassis Control Module On Chassis Expansion CAN Bus - AutoCodes.com — U18AC Chevrolet Code - Transmission Range Control Module Lost Communication With Chassis Control Module On Chassis Expansion CAN Bus

What does this mean?

What are the Possible Causes of the DTC U18AC Chevrolet?

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

How to Fix the DTC U18AC Chevrolet?

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 U18AC Chevrolet 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.

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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 U18AC Chevrolet Code

1. What are the common symptoms of OBDII code U18AC in a Chevrolet related to Transmission Range Control Module communication loss?

The common symptoms include erratic shifting, transmission slipping, inability to shift gears, and illuminated warning lights on the dashboard.

2. What are the potential causes of U18AC code in a Chevrolet indicating Transmission Range Control Module lost communication with Chassis Control Module?

Possible causes include damaged wiring or connectors in the CAN bus system, faulty control modules, software issues, or a poor connection in the communication network.

3. How can I diagnose the U18AC code in my Chevrolet if the Transmission Range Control Module lost communication with the Chassis Control Module?

A thorough inspection of the CAN bus wiring, connectors, and modules is recommended. Using a diagnostic scanner to check for other related trouble codes can also help pinpoint the issue.

4. Can I continue driving my Chevrolet with the U18AC code showing Transmission Range Control Module communication loss?

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

5. How can I repair the U18AC code in my Chevrolet indicating communication loss between the Transmission Range Control Module and Chassis Control Module?

Repairing this code may involve fixing wiring or connector issues, replacing faulty control modules, updating software, or ensuring proper communication network connections.

6. Is it possible to reset the U18AC code in a Chevrolet without addressing the underlying issue?

Resetting the code without fixing the root cause may temporarily clear the warning light, but the issue will likely reoccur, leading to potential transmission problems.

7. Are there any specific Chevrolet models known to be prone to experiencing the U18AC code related to Transmission Range Control Module communication loss?

While this code can occur in various Chevrolet models, some vehicles with complex CAN bus systems may be more susceptible to communication issues between control modules.

8. Can a DIY enthusiast with basic automotive knowledge attempt to diagnose and repair the U18AC code in a Chevrolet?

While some simple checks like inspecting wiring connections can be done by DIY enthusiasts, diagnosing and repairing complex communication issues may require professional expertise and specialized tools.

9. Will fixing the U18AC code in a Chevrolet require reprogramming or relearning procedures after the repair?

In some cases, after fixing the communication issue, reprogramming or performing relearn procedures on the control modules may be necessary to ensure proper functionality and communication between modules.

10. How can regular maintenance and inspections help prevent the U18AC code related to communication loss between the Transmission Range Control Module and Chassis Control Module in a Chevrolet?

Regular maintenance, including checking and cleaning connectors, inspecting wiring harnesses, and keeping the vehicle's software up to date, can help prevent communication issues leading to the U18AC code.