AutoCodes – Chevrolet – U1804 Chevrolet

U1804 Chevrolet Code - Lost Communication With Inside Rearview Mirror Control Module

Quick Answer

Modules connected to the Controller Area Network (CAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Inside Rearview Mirror Control Module, Inside Rearview Mirror Control Module harness is open or shorted, Inside Rearview Mirror 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: U1804 Chevrolet indicates Lost Communication With Inside Rearview Mirror Control Module.
Common causes: Common causes include Faulty Inside Rearview Mirror Control Module, Inside Rearview Mirror Control Module harness is open or shorted, Inside Rearview Mirror 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 1,329

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 07, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1804 Chevrolet Description

Modules connected to the Controller Area Network (CAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module. A module with a CAN serial data circuits malfunction or which loses power during the current ignition cycle will have a Loss of Communication Diagnostic Trouble Code (DTC) set by other modules that depend on information from that failed module. If any of the CAN circuit are shorted to battery voltage, ground, or between them no communication is possible on the CAN serial data bus, a Diagnostic Trouble Code will set.

OBDII Code U1804 Chevrolet - Lost Communication With Inside Rearview Mirror Control Module - AutoCodes.com — U1804 Chevrolet Code - Lost Communication With Inside Rearview Mirror Control Module

What does this mean?

What are the Possible Causes of the DTC U1804 Chevrolet?

Faulty Inside Rearview Mirror Control Module
Inside Rearview Mirror Control Module harness is open or shorted
Inside Rearview Mirror Control Module circuit poor electrical connection

How to Fix the DTC U1804 Chevrolet?

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 U1804 Chevrolet 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 U1804 Chevrolet Code

1. What are the common symptoms of OBDII code U1804 Chevrolet (Lost Communication With Inside Rearview Mirror Control Module)?

- Common symptoms include the interior rearview mirror not functioning properly, loss of control over mirror adjustments, and warning lights on the dashboard.

2. What are some possible causes of OBDII code U1804 Chevrolet?

- Possible causes may include a faulty inside rearview mirror control module, damaged wiring or connectors, issues with the vehicle's electrical system, or a communication error within the network.

3. How can I diagnose the cause of OBDII code U1804 Chevrolet?

- You can diagnose the issue by inspecting the wiring and connectors related to the inside rearview mirror control module, checking for any visible damage, performing a scan with an OBDII scanner to pinpoint the communication error, and testing the module itself for functionality.

4. Can I still drive my vehicle with OBDII code U1804 Chevrolet present?

- It is generally safe to drive your vehicle with this code, as it primarily affects the functionality of the inside rearview mirror control module and does not impact the driving performance or safety of the vehicle.

5. How can I repair OBDII code U1804 Chevrolet?

- Repairing this code may involve replacing the inside rearview mirror control module, repairing any damaged wiring or connectors, resetting the module's programming, or seeking professional help for further diagnosis and repair.

6. Are there any DIY tips for fixing OBDII code U1804 Chevrolet?

- DIY tips may include checking and securing all wiring connections related to the inside rearview mirror, inspecting for any visible damage, and ensuring proper power supply to the control module.

7. Can a simple reset fix OBDII code U1804 Chevrolet?

- A simple reset or disconnecting the battery for a few minutes may temporarily clear the code, but it is recommended to diagnose and address the root cause to prevent the code from reoccurring.

8. How common is OBDII code U1804 Chevrolet in vehicles?

- This code is relatively uncommon compared to other OBDII codes, as it specifically relates to a communication error with the inside rearview mirror control module, which not all vehicles may have.

9. Will OBDII code U1804 Chevrolet cause my vehicle to fail an emissions test?

- This code is unlikely to cause your vehicle to fail an emissions test, as it does not directly affect the emissions-related components or systems of the vehicle.

10. Is it safe to ignore OBDII code U1804 Chevrolet if my vehicle is running fine?

- While you may continue driving with this code if your vehicle is running fine, it is recommended to address the issue to ensure proper functionality of the inside rearview mirror control module and prevent any potential future complications.