AutoCodes – GMC – U1894 GMC

U1894 GMC Code - Hybrid Control Module Lost Communication With Starter/Generator Control Module

Quick Answer

Modules connected to the class 2 and high-speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Starter/Generator Control Module (SGCM), Starter/Generator Control Module harness is open or shorted, Starter/Generator 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: U1894 GMC indicates Hybrid Control Module Lost Communication With Starter/Generator Control Module.
Common causes: Common causes include Faulty Starter/Generator Control Module (SGCM), Starter/Generator Control Module harness is open or shorted, Starter/Generator 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 501

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 Jun 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1894 GMC Description

Modules connected to the class 2 and high-speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The Diagnostic Trouble Code (DTC) is reported on a class 2 link to the scan tool by Powertrain Control Module (PCM) even if they may be set by different modules. The DTC will set when a node alive message has not been received from an identified module within the last 5 seconds after establishing class 2 serial data communication, or a supervised high-speed GMLAN message has not been received.

OBDII Code U1894 GMC - Hybrid Control Module Lost Communication With Starter/Generator Control Module - AutoCodes.com — U1894 GMC Code - Hybrid Control Module Lost Communication With Starter/Generator Control Module

What does this mean?

What are the Possible Causes of the DTC U1894 GMC?

Faulty Starter/Generator Control Module (SGCM)
Starter/Generator Control Module harness is open or shorted
Starter/Generator Control Module circuit poor electrical connection
Faulty Hybrid Control Module (HCM)

How to Fix the DTC U1894 GMC?

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 U1894 GMC 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 U1894 GMC Code

1. What are the common symptoms of OBDII code U1894 in a GMC vehicle?

The common symptoms of U1894 code include the vehicle not starting, reduced fuel efficiency, and the hybrid system malfunction indicator light illuminating.

2. What can cause the OBDII code U1894 in a GMC vehicle?

The U1894 code is typically caused by a communication error between the Hybrid Control Module and the Starter/Generator Control Module in the hybrid system.

3. How can I diagnose the OBDII code U1894 in my GMC vehicle?

Diagnosing the U1894 code involves using a professional OBDII scanner to retrieve the fault codes and then performing a detailed inspection of the hybrid system components for any visible issues or wiring problems.

4. Can a faulty battery or charging system trigger the U1894 code in a GMC vehicle?

Yes, a faulty battery or charging system can potentially trigger the U1894 code due to the impact on the communication between the Hybrid Control Module and the Starter/Generator Control Module.

5. What are some repair tips for resolving the OBDII code U1894 in a GMC vehicle?

Repair tips for resolving the U1894 code may include checking and repairing any damaged wiring, ensuring proper connection between modules, and resetting the fault codes after the repair.

6. Is it safe to continue driving with the U1894 code present in a GMC vehicle?

It is not recommended to continue driving with the U1894 code present, as it can lead to further damage to the hybrid system components and potentially affect the vehicle's performance.

7. Can the U1894 code be intermittent in nature in a GMC vehicle?

Yes, the U1894 code can be intermittent, meaning that the communication error between the hybrid modules may not occur consistently, making diagnosis and repair more challenging.

8. How much does it typically cost to repair the OBDII code U1894 in a GMC vehicle?

The cost of repairing the U1894 code can vary depending on the underlying issue, but it may involve labor costs for diagnosis and repair, as well as potential costs for replacing damaged components.

9. Are there any recalls or technical service bulletins related to the U1894 code in GMC vehicles?

It is recommended to check with a GMC dealership or the manufacturer's website for any recalls or technical service bulletins related to the U1894 code to see if there are any known issues or solutions provided.

10. Can a DIY enthusiast with some automotive experience attempt to fix the U1894 code in a GMC vehicle?

While some basic troubleshooting steps can be taken by a DIY enthusiast, resolving the U1894 code may require specialized tools and expertise, so it is advisable to consult a professional mechanic for proper diagnosis and repair.