AutoCodes – Cadillac – U1128 Cadillac

U1128 Cadillac Code - Lost Communications With Radio

Quick Answer

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Common causes include Faulty Radio, Radio harness is open or shorted, Radio 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: U1128 Cadillac indicates Lost Communications With Radio.
Common causes: Common causes include Faulty Radio, Radio harness is open or shorted, Radio 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 1,186

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 Apr 22, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1128 Cadillac Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the identification number of the module which sent the message for the state of health monitoring/node alive messages. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once an identification number is learned by a module, it will monitor for that module node alive message. Each module on the class 2 serial data circuit is required to send a Node Alive message every 2 seconds. When no message is detected from a learned identification number for 5 seconds, a Diagnostic Trouble Code (DTC) U1128 is set.

OBDII Code U1128 Cadillac - Lost Communications With Radio - AutoCodes.com — U1128 Cadillac Code - Lost Communications With Radio

What does this mean?

What are the Possible Causes of the DTC U1128 Cadillac?

Faulty Radio
Radio harness is open or shorted
Radio circuit poor electrical connection

How to Fix the DTC U1128 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 U1128 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 U1128 Cadillac Code

1. What does the OBDII code U1128 mean on a Cadillac?

The U1128 code indicates a loss of communication between the vehicle's radio and other control modules on the communication network.

2. What are the symptoms of code U1128 on a Cadillac?

Symptoms may include the radio not working, loss of infotainment functions, blank display screens, or intermittent audio issues.

3. What causes the U1128 code to appear on a Cadillac?

Common causes include a faulty radio unit, wiring or connection issues in the communication network, or a malfunctioning control module.

4. Can a bad battery cause the U1128 code on my Cadillac?

Yes, a weak or failing battery can cause communication errors, including the U1128 code, due to voltage drops affecting the network.

5. How do I diagnose the U1128 code on a Cadillac?

Start by checking for related codes, inspecting wiring and connections to the radio, and testing the radio module's power and ground circuits.

6. Is it safe to drive with the U1128 code on my Cadillac?

Yes, it is typically safe to drive, but you may lose access to radio and infotainment features, which could be inconvenient.

7. How can I fix the U1128 code on a Cadillac?

Repairs may include resecuring or replacing damaged wiring, updating software on the radio or control modules, or replacing a faulty radio unit.

8. Can a software update resolve the U1128 code on my Cadillac?

Yes, if the issue is caused by a software glitch in the radio or a related module, an update may resolve the problem.

9. How much does it cost to fix the U1128 code on a Cadillac?

Repair costs vary but can range from $100 for simple wiring fixes to over $1,000 if the radio module needs replacement.

10. Do I need a professional to repair the U1128 code on my Cadillac?

While some issues, like checking connections, can be handled by experienced DIYers, professional diagnostics may be required for module programming or advanced troubleshooting.