AutoCodes – Generic – U1800

U1800 Code - Lost Communications With Fuel Injector 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 Fuel Injector Control Module (FICM), Fuel Injector Control Module harness is open or shorted, Fuel Injector 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: U1800 indicates Lost Communications With Fuel Injector Control Module.
Common causes: Common causes include Faulty Fuel Injector Control Module (FICM), Fuel Injector Control Module harness is open or shorted, Fuel Injector 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 4,051

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 U1800 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 U1800 - Lost Communications With Fuel Injector Control Module - AutoCodes.com — U1800 Code - Lost Communications With Fuel Injector Control Module

What does this mean?

What are the Possible Causes of the DTC U1800?

Faulty Fuel Injector Control Module (FICM)
Fuel Injector Control Module harness is open or shorted
Fuel Injector Control Module circuit poor electrical connection

How to Fix the DTC U1800?

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 U1800 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 U1800 code?

Need more information on how to fix the U1800 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1800 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U1800 Buick — Lost Communications With Fuel Injector Control Module
U1800 Cadillac — Lost Communications With Fuel Injector Control Module
U1800 Chevrolet — Lost Communications With Fuel Injector Control Module
U1800 GMC — Lost Communications With Fuel Injector 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 U1800 Code

1. What are the common symptoms of OBDII code U1800 - Lost Communications With Fuel Injector Control Module?

- Common symptoms include rough idle, engine misfires, stalling, poor fuel economy, and difficulty starting the vehicle.

2. What are the possible causes of OBDII code U1800?

- The code U1800 can be triggered by issues such as a faulty fuel injector control module, damaged wiring or connectors, a blown fuse, or a communication failure within the vehicle's network.

3. How can I diagnose the cause of OBDII code U1800?

- Diagnosing the cause of code U1800 typically involves using a scan tool to retrieve the code, checking for any related codes, inspecting wiring and connectors for damage, and testing the fuel injector control module.

4. What are some repair tips for addressing OBDII code U1800?

- Repair tips may include checking and repairing any damaged wiring or connectors, replacing a faulty fuel injector control module, ensuring all fuses related to the module are intact, and performing a thorough inspection of the vehicle's communication network.

5. Can I drive my vehicle with OBDII code U1800 present?

- It is generally not recommended to drive your vehicle with code U1800 present, as it can lead to poor engine performance and potential further damage. It is advisable to address the issue promptly.

6. How much does it typically cost to repair OBDII code U1800?

- The cost of repairing code U1800 can vary depending on the root cause of the issue, the labor rates in your area, and the cost of any necessary parts. It is recommended to consult with a professional mechanic for an accurate estimate.

7. Are there any DIY fixes for OBDII code U1800?

- While some basic troubleshooting steps can be taken, such as checking for loose connectors or blown fuses, diagnosing and repairing code U1800 often requires specialized tools and expertise. It is advisable to seek professional help for proper diagnosis and repair.

8. How long does it take to repair OBDII code U1800?

- The repair time for code U1800 can vary depending on the specific cause of the issue and the complexity of the repair. It may take anywhere from a few hours to a full day to diagnose and fix the problem.

9. Can a vehicle still pass an emissions test with OBDII code U1800?

- A vehicle with an unresolved OBDII code U1800 is likely to fail an emissions test, as the issue can affect the vehicle's emissions control system and overall performance. It is recommended to address the code before attempting an emissions test.

10. What should I do if OBDII code U1800 keeps coming back after repairs?

- If code U1800 keeps reoccurring after repairs, it may indicate an underlying issue that has not been fully addressed. It is important to recheck the repairs, conduct a thorough diagnostic, and ensure all related components are functioning properly to prevent the code from returning.