AutoCodes – Generic – U18AA

U18AA Code - Transmission Range Control Module Lost Communication With Engine Control Module

Quick Answer

Devices connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Engine Control Module (ECM), Engine Control Module harness is open or shorted, Engine 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: U18AA indicates Transmission Range Control Module Lost Communication With Engine Control Module.
Common causes: Common causes include Faulty Engine Control Module (ECM), Engine Control Module harness is open or shorted, Engine 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 809

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 U18AA 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 U18AA - Transmission Range Control Module Lost Communication With Engine Control Module - AutoCodes.com — U18AA Code - Transmission Range Control Module Lost Communication With Engine Control Module

What does this mean?

What are the Possible Causes of the DTC U18AA?

Faulty Engine Control Module (ECM)
Engine Control Module harness is open or shorted
Engine Control Module circuit poor electrical connection

How to Fix the DTC U18AA?

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 U18AA 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 U18AA code?

Need more information on how to fix the U18AA code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U18AA code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U18AA Buick — Transmission Range Control Module Lost Communication With Engine Control Module
U18AA Cadillac — Transmission Range Control Module Lost Communication With Engine Control Module
U18AA Chevrolet — Transmission Range Control Module Lost Communication With Engine Control Module
U18AA GMC — Transmission Range Control Module Lost Communication With Engine Control Module

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 U18AA Code

1. What are the common symptoms of OBDII code U18AA?

- Common symptoms include transmission shifting issues, engine stalling, and the illumination of the check engine light.

2. What can cause the OBDII code U18AA to trigger?

- The code U18AA may trigger when there is a communication breakdown between the Transmission Range Control Module and the Engine Control Module.

3. How serious is the U18AA code?

- The U18AA code is considered serious as it can lead to drivability issues and potential safety concerns if not addressed promptly.

4. How can I diagnose the U18AA code?

- Diagnosing the U18AA code typically involves using a diagnostic scanner to retrieve the code, checking for any other related codes, and performing a communication test between modules.

5. What are the possible repair options for the U18AA code?

- Repair options may include checking and repairing any damaged wiring or connectors, reprogramming or replacing the affected modules, and ensuring all software updates are current.

6. Can I drive my vehicle with the U18AA code present?

- It is not recommended to drive your vehicle with the U18AA code present, as it can lead to further damage and safety risks.

7. How much does it cost to repair the U18AA code?

- The cost of repairing the U18AA code can vary depending on the exact cause of the communication issue, but it may involve labor costs for diagnosis and parts replacement.

8. Can I reset the U18AA code on my own?

- While you can attempt to clear the code with a diagnostic scanner, it is important to address the underlying issue causing the code to prevent it from reoccurring.

9. How long does it take to repair the U18AA code?

- The repair time for the U18AA code can vary depending on the complexity of the issue and the availability of parts, but it may take a few hours to a full day.

10. Is the U18AA code specific to certain vehicle makes and models?

- The U18AA code may be specific to certain vehicle makes and models, so it is important to consult your vehicle's specific diagnostic information for accurate troubleshooting.