AutoCodes – GMC – U18A7 GMC

U18A7 GMC Code - Lost Communication With Power Supply Transformer On Powertrain 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 Power Supply Transformer, Power Supply Transformer harness is open or shorted, Power Supply Transformer 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: U18A7 GMC indicates Lost Communication With Power Supply Transformer On Powertrain Expansion CAN Bus.
Common causes: Common causes include Faulty Power Supply Transformer, Power Supply Transformer harness is open or shorted, Power Supply Transformer 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 1,137

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 U18A7 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 U18A7 GMC - Lost Communication With Power Supply Transformer On Powertrain Expansion CAN Bus - AutoCodes.com — U18A7 GMC Code - Lost Communication With Power Supply Transformer On Powertrain Expansion CAN Bus

What does this mean?

What are the Possible Causes of the DTC U18A7 GMC?

Faulty Power Supply Transformer
Power Supply Transformer harness is open or shorted
Power Supply Transformer circuit poor electrical connection

How to Fix the DTC U18A7 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 U18A7 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 U18A7 GMC Code

1. What are the common symptoms of OBDII code U18A7 GMC?

- Common symptoms include issues with the vehicle's powertrain performance, such as engine stalling, rough idling, or difficulty starting.

2. What are the possible causes of OBDII code U18A7 GMC?

- The code U18A7 GMC typically indicates a communication problem with the power supply transformer on the powertrain expansion CAN bus. Possible causes may include wiring issues, a faulty power supply transformer, or a malfunctioning CAN bus module.

3. How can I diagnose OBDII code U18A7 GMC?

- Diagnosing this code usually involves a thorough inspection of the wiring related to the power supply transformer, checking the power supply transformer itself for faults, and using a diagnostic scanner to read the trouble codes and monitor communication on the CAN bus.

4. Can I drive my vehicle with OBDII code U18A7 GMC?

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

5. How do I repair OBDII code U18A7 GMC?

- Repairing this code may involve fixing any wiring issues, replacing the power supply transformer if faulty, or addressing any problems with the CAN bus module. It is advisable to seek assistance from a qualified mechanic for proper diagnosis and repair.

6. Is OBDII code U18A7 GMC a serious issue?

- Yes, this code should be addressed promptly to prevent further damage to the powertrain system and ensure the vehicle operates correctly.

7. Can a DIY enthusiast fix OBDII code U18A7 GMC?

- While basic troubleshooting like checking for loose connections or damaged wiring may be possible for some DIY enthusiasts, diagnosing and repairing this code often requires specialized tools and expertise best left to professional mechanics.

8. How much does it cost to repair OBDII code U18A7 GMC?

- The cost of repairing this code can vary depending on the underlying cause of the issue, the extent of the repairs needed, and the labor rates in your area. It's advisable to get a diagnostic assessment from a mechanic for an accurate cost estimate.

9. Will OBDII code U18A7 GMC cause my vehicle to fail emissions testing?

- Yes, if this code is present during an emissions test, it will likely cause your vehicle to fail. It's important to address the issue promptly to ensure your vehicle meets emissions standards.

10. How can I prevent OBDII code U18A7 GMC from recurring?

- To prevent this code from recurring, it's essential to address any underlying issues promptly, perform regular maintenance on your vehicle's electrical system, and ensure all connections are secure and free of corrosion.