AutoCodes – Cadillac – U18AA Cadillac

U18AA Cadillac 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 Cadillac 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 746

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

What does this mean?

What are the Possible Causes of the DTC U18AA Cadillac?

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 Cadillac?

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 Cadillac 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 U18AA Cadillac Code

1. What are the common symptoms of OBDII code U18AA in a Cadillac related to the Transmission Range Control Module lost communication with the Engine Control Module?

- Common symptoms include issues with shifting gears, transmission slipping, rough shifting, and possible limp mode activation.

2. What are the possible causes of the U18AA code in a Cadillac?

- The U18AA code can be triggered by issues such as damaged wiring, faulty connectors, a malfunctioning Transmission Range Control Module, or a problem with the Engine Control Module.

3. How can I diagnose the U18AA code in my Cadillac?

- Proper diagnosis involves using a professional OBDII scanner to retrieve the code, checking the wiring and connectors for any damage, and testing the Transmission Range Control Module and Engine Control Module for functionality.

4. Can I drive my Cadillac with the U18AA code present?

- It is not recommended to drive your Cadillac with the U18AA code present, as it can lead to serious transmission problems and potentially cause further damage to the vehicle.

5. How can I repair the U18AA code in my Cadillac?

- Repairing the U18AA code may involve repairing or replacing damaged wiring, connectors, or modules, resetting the codes, and ensuring proper communication between the Transmission Range Control Module and Engine Control Module.

6. Is it safe to continue driving if the U18AA code disappears on its own?

- Even if the U18AA code disappears on its own, it is still advisable to have your Cadillac inspected by a professional to ensure that the underlying issue has been properly addressed to prevent future problems.

7. Can a DIY enthusiast fix the U18AA code issue in a Cadillac?

- While some basic troubleshooting steps can be performed by a DIY enthusiast, it is recommended to seek professional help for diagnosing and repairing the U18AA code to ensure the proper functioning of your Cadillac.

8. How much does it cost to repair the U18AA code in a Cadillac?

- The cost of repairing the U18AA code can vary depending on the extent of the issue, the parts that need to be replaced, and the labor costs. It is best to consult with a mechanic for an accurate estimate.

9. Will resetting the U18AA code make it go away permanently?

- Resetting the U18AA code may temporarily clear the code, but if the underlying issue is not resolved, the code is likely to reappear. It is important to address the root cause of the problem for a permanent solution.

10. How long does it take to repair the U18AA code in a Cadillac?

- The repair time for the U18AA code can vary based on the specific issue causing the code and the availability of parts. It is recommended to consult with a mechanic for an estimated repair timeline.