AutoCodes – GMC – U18A1 GMC

U18A1 GMC Code - Lost Communication With Coolant Temperature Control Module On High Voltage Energy Management CAN Bus

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Coolant Temperature Control Module, Coolant Temperature Control Module harness is open or shorted, Coolant Temperature 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: U18A1 GMC indicates Lost Communication With Coolant Temperature Control Module On High Voltage Energy Management CAN Bus.
Common causes: Common causes include Faulty Coolant Temperature Control Module, Coolant Temperature Control Module harness is open or shorted, Coolant Temperature 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 541

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 U18A1 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 U18A1 GMC - Lost Communication With Coolant Temperature Control Module On High Voltage Energy Management CAN Bus - AutoCodes.com — U18A1 GMC Code - Lost Communication With Coolant Temperature Control Module On High Voltage Energy Management CAN Bus

What does this mean?

What are the Possible Causes of the DTC U18A1 GMC?

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

How to Fix the DTC U18A1 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 U18A1 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.

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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 U18A1 GMC Code

1. What are the common symptoms of OBDII code U18A1 in a GMC vehicle?

- Common symptoms include the check engine light coming on, issues with coolant temperature control, and potential loss of communication with the module.

2. What could cause the U18A1 code to trigger in a GMC vehicle?

- The code may be triggered due to a faulty coolant temperature control module, wiring issues, or problems with the high voltage energy management CAN bus.

3. How can I diagnose the root cause of the U18A1 code in my GMC vehicle?

- Diagnosis typically involves checking the coolant temperature control module, inspecting the wiring for any damage, and using a professional diagnostic tool to scan for communication errors.

4. Is it safe to drive with the U18A1 trouble code present in a GMC vehicle?

- It is not recommended to drive with the U18A1 code present, as it can lead to incorrect temperature readings and potential issues with engine performance.

5. What are some tips for repairing the U18A1 code in a GMC vehicle?

- Repair tips may include checking and repairing any damaged wiring, replacing the coolant temperature control module if necessary, and clearing the code with a diagnostic tool.

6. Can a DIY enthusiast fix the U18A1 code issue in a GMC vehicle?

- While some basic troubleshooting steps can be performed by a DIY enthusiast, it is recommended to consult a professional mechanic for a thorough diagnosis and repair of the U18A1 code.

7. How much does it cost to repair the U18A1 code in a GMC vehicle?

- Repair costs can vary depending on the root cause of the issue, but expenses may include parts replacement, labor charges, and diagnostic fees.

8. Will resetting the trouble codes make the U18A1 code disappear permanently?

- Resetting the trouble codes may temporarily clear the U18A1 code, but if the underlying issue is not addressed, the code is likely to reappear.

9. Can the U18A1 code affect the overall performance of a GMC vehicle?

- Yes, the U18A1 code can impact the performance of a GMC vehicle by causing issues with coolant temperature control and communication with the relevant module.

10. Is the U18A1 code specific to GMC vehicles only?

- The U18A1 code may be specific to GMC vehicles, as it relates to communication issues with the coolant temperature control module on the high voltage energy management CAN bus.