AutoCodes – Generic – U1894

U1894 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 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 659

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 08, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code U1894 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 - Hybrid Control Module Lost Communication With Starter/Generator Control Module - AutoCodes.com — U1894 Code - Hybrid Control Module Lost Communication With Starter/Generator Control Module

What does this mean?

What are the Possible Causes of the DTC U1894?

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?

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 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 U1894 code?

Need more information on how to fix the U1894 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the U1894 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

U1894 Buick — Hybrid Control Module Lost Communication With Starter/Generator Control Module
U1894 Cadillac — Hybrid Control Module Lost Communication With Starter/Generator Control Module
U1894 Chevrolet — Hybrid Control Module Lost Communication With Starter/Generator Control Module
U1894 GMC — Hybrid Control Module Lost Communication With Starter/Generator 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 U1894 Code

1. What does the OBDII code U1894 mean?

The U1894 code indicates that the Hybrid Control Module (HCM) has lost communication with the Starter/Generator Control Module (SGCM), which is critical for hybrid system operation.

2. What are the common symptoms of the U1894 code?

Common symptoms include the check engine light turning on, reduced hybrid system performance, failure to start, or the vehicle switching to limp mode.

3. What causes the U1894 code to appear?

The code can be caused by issues such as damaged wiring, loose or corroded connections, a faulty Hybrid Control Module, a malfunctioning Starter/Generator Control Module, or software glitches.

4. Can I drive with the U1894 code active?

Driving with this code is not recommended, as it could lead to reduced performance or potential failure of the hybrid system, possibly leaving you stranded.

5. How can I diagnose the U1894 code?

Diagnose the issue by inspecting the wiring and connectors between the HCM and SGCM, checking for communication signals using a scan tool, and testing both modules for proper operation.

6. Is the U1894 code specific to certain vehicles?

Yes, this code is typically found in hybrid vehicles, and its occurrence depends on the specific make and model with hybrid systems.

7. What repairs are commonly needed for the U1894 code?

Repairs may include fixing or replacing damaged wires, cleaning or securing connectors, reprogramming or replacing the Hybrid Control Module, or replacing the Starter/Generator Control Module.

8. How much does it cost to fix the U1894 code?

Repair costs can vary widely, from $100 to $1,000 or more, depending on whether the issue involves simple wiring repairs or module replacements.

9. Can software updates resolve the U1894 code?

In some cases, a software update or reprogramming of the Hybrid Control Module or Starter/Generator Control Module may resolve the issue.

10. How can I prevent the U1894 code from returning?

To prevent recurrence, ensure regular inspection and maintenance of the hybrid system wiring, connectors, and modules, and address any issues promptly.