AutoCodes – Buick – U18A7 Buick

U18A7 Buick 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 Buick 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 1,057

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

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 Buick?

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 Buick 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 Buick Code

1. What does the OBDII code U18A7 mean on a Buick?

U18A7 indicates a loss of communication with the Power Supply Transformer on the Powertrain Expansion CAN Bus, which can affect the vehicle's communication network.

2. What are common symptoms of the U18A7 code in a Buick?

Symptoms may include the check engine light turning on, erratic engine performance, intermittent power loss, or issues with electronic systems like the transmission or fuel delivery.

3. What causes the U18A7 code to appear?

This code is typically caused by a faulty power supply transformer, damaged wiring, a loose or corroded connector, or issues with the CAN bus communication network.

4. Can I drive my Buick with the U18A7 code active?

While the vehicle may still be drivable, it is not recommended as the code could lead to further system malfunctions or reduced engine performance.

5. How is the U18A7 code diagnosed?

A technician will use an advanced scan tool to check for communication errors, inspect wiring and connectors, and test the power supply transformer for proper operation.

6. What is the most common fix for the U18A7 code?

The most common repair involves repairing or replacing damaged wiring, securing loose connectors, or replacing a defective power supply transformer.

7. Can the U18A7 code be caused by a dead battery?

Yes, a weak or dead battery can disrupt the CAN bus communication network, potentially triggering the U18A7 code.

8. How much does it cost to fix the U18A7 code on a Buick?

Repair costs can vary, but diagnosing and repairing wiring or connector issues typically ranges from $100 to $500, depending on labor and parts.

9. Can I reset the U18A7 code by disconnecting the battery?

Disconnecting the battery may temporarily clear the code, but the underlying issue must be resolved to prevent it from reoccurring.

10. What tools are needed to troubleshoot the U18A7 code?

A professional-grade OBDII scan tool capable of reading CAN bus communication errors, a multimeter, and wiring diagrams for your Buick are essential for troubleshooting.