AutoCodes – Cadillac – U1166 Cadillac

U1166 Cadillac Code - Lost Communications With Driver Seat Module

Quick Answer

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Common causes include Faulty Driver Seat Module, Driver Seat Module harness is open or shorted, Driver Seat 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: U1166 Cadillac indicates Lost Communications With Driver Seat Module.
Common causes: Common causes include Faulty Driver Seat Module, Driver Seat Module harness is open or shorted, Driver Seat 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 551

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Apr 24, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1166 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) U1166 is set.

OBDII Code U1166 Cadillac - Lost Communications With Driver Seat Module - AutoCodes.com — U1166 Cadillac Code - Lost Communications With Driver Seat Module

What does this mean?

What are the Possible Causes of the DTC U1166 Cadillac?

Faulty Driver Seat Module
Driver Seat Module harness is open or shorted
Driver Seat Module circuit poor electrical connection

How to Fix the DTC U1166 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 U1166 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 U1166 Cadillac Code

1. What does the OBDII code U1166 mean on a Cadillac?

U1166 indicates a loss of communication with the Driver Seat Module (DSM), meaning the vehicle's systems are unable to communicate with this module properly.

2. What are the common symptoms of the U1166 code?

Symptoms may include unresponsive power seat adjustments, memory seat functions not working, dashboard warning lights, or intermittent seat module operation.

3. What causes the U1166 code to appear?

Common causes include a faulty Driver Seat Module, damaged wiring or connectors, issues with the CAN bus network, or a blown fuse related to the DSM.

4. Can a weak battery cause the U1166 code?

Yes, a weak or failing battery can disrupt communication between modules, potentially triggering the U1166 code.

5. How do I diagnose the U1166 code on a Cadillac?

Start by checking the DSM wiring and connectors for damage or corrosion. Use a scan tool to check for additional codes and verify communication on the CAN bus network.

6. Can I still drive my Cadillac with the U1166 code active?

Yes, the vehicle is typically drivable, but seat adjustments or memory functions may not work. It's best to address the issue promptly to prevent further electrical problems.

7. How do I fix the U1166 code on my Cadillac?

Repairs may involve replacing or repairing damaged wiring, cleaning corroded connectors, resetting the control module, or replacing the Driver Seat Module if faulty.

8. Will clearing the U1166 code solve the problem?

Clearing the code may temporarily remove it, but it will likely return if the underlying issue is not resolved.

9. How much does it cost to fix the U1166 code?

Repair costs can vary widely, from $50 for minor wiring repairs to over $500 if the Driver Seat Module needs replacement.

10. Can a software update fix the U1166 code?

In some cases, a software update for the vehicle's control modules may resolve communication issues. Consult your dealership or a qualified technician for advice.