AutoCodes – Generic – U18A7

U18A7 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 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 2,946

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

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?

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 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 U18A7 code?

Need more information on how to fix the U18A7 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U18A7 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U18A7 Buick — Lost Communication With Power Supply Transformer On Powertrain Expansion CAN Bus
U18A7 Cadillac — Lost Communication With Power Supply Transformer On Powertrain Expansion CAN Bus
U18A7 Chevrolet — Lost Communication With Power Supply Transformer On Powertrain Expansion CAN Bus
U18A7 GMC — Lost Communication With Power Supply Transformer On Powertrain Expansion CAN Bus

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 Code

What are common symptoms of OBDII code U18A7?

- Common symptoms include the check engine light illuminating on the dashboard, issues with the powertrain system, and potential loss of communication with components on the Powertrain Expansion CAN Bus.

What can cause the OBDII code U18A7 to appear?

- This code can be triggered by a malfunction in the power supply transformer or issues with the communication network on the Powertrain Expansion CAN Bus.

How can I diagnose the issue related to code U18A7?

- Diagnosing the issue may involve checking the power supply transformer, inspecting the wiring and connectors in the Powertrain Expansion CAN Bus, and using a diagnostic scanner to read the fault codes.

Is it safe to drive with the U18A7 trouble code?

- It is not recommended to drive with the U18A7 trouble code present, as it may affect the performance and safety of the vehicle. It is best to address the issue promptly.

What are some repair tips for fixing code U18A7?

- Repair tips may include checking and replacing the power supply transformer, inspecting and repairing any damaged wiring or connectors, and ensuring proper communication on the Powertrain Expansion CAN Bus.

Can a DIY enthusiast fix the U18A7 trouble code?

- While some aspects of diagnosing and repairing the U18A7 trouble code may be within reach of a DIY enthusiast, it is recommended to seek professional help to ensure the issue is properly addressed.

How much does it cost to repair the U18A7 code?

- The cost of repairing the U18A7 code can vary depending on the underlying cause of the issue, the extent of the repairs needed, and labor rates in your area. It is advisable to get a few quotes from reputable mechanics.

Will resetting the trouble codes make the U18A7 code disappear?

- Resetting the trouble codes may temporarily clear the U18A7 code, but if the underlying issue is not addressed, the code is likely to reappear. It is important to diagnose and repair the root cause of the problem.

Is the U18A7 trouble code specific to certain vehicle makes and models?

- The U18A7 trouble code is specific to vehicles equipped with an OBDII system and a Powertrain Expansion CAN Bus. It may appear in various makes and models that use this technology.