AutoCodes – Hummer – U0100 Hummer

U0100 Hummer Code - Lost Communication With Engine Control Module

Quick Answer

Modules connected to the high-speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Faulty Engine Control Module (ECM), ECM harness is open or shorted, ECM 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: U0100 Hummer indicates Lost Communication With Engine Control Module.
Common causes: Common causes include Faulty Engine Control Module (ECM), ECM harness is open or shorted, ECM 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 5,093

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 29, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code U0100 Hummer Description

Modules connected to the 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 modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised, and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. The supervision time-out period is 250 ms. Each message contains the identification number of the transmitter module.
The serial data circuit is how the devices in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the Data Link Connector (DLC), the scan tool can be used to monitor each device for diagnostic purposes and to check for Diagnostic Trouble Codes (DTC). When the ignition switch is in RUN, each device communicating on the serial data circuit sends a state of health message to ensure that the device is operating correctly. When a device stops communicating on the serial data circuit, for example, if the device loses power or ground, the state of health message, it normally sends on the serial data circuit disappears. Other devices on the serial data circuit, which expect to receive that state of health message, detect its absence; those devices, in turn, set a DTC associated with the loss of the state of health of the non-communicating device. The DTC is unique to the device which is not communicating, and one or more devices may set the same code. A loss of serial data communications DTC does not represent a failure of the devices that contain the stored code.

OBDII Code U0100 Hummer - Lost Communication With Engine Control Module - AutoCodes.com — U0100 Hummer Code - Lost Communication With Engine Control Module

What does this mean?

What are the Possible Causes of the DTC U0100 Hummer?

Faulty Engine Control Module (ECM)
ECM harness is open or shorted
ECM circuit poor electrical connection

How to Fix the DTC U0100 Hummer?

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 does this mean?

Code Tech Notes

There is a factory service bulletin for the 2008-2009 HUMMER H2:
2008-2009 HUMMER H2 Factory Service Bulletin OBDII Code U0100

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0100 Hummer 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 U0100 Hummer code?

Need more information on how to fix the U0100 Hummer code? Get Access to Factory Service Manuals

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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 U0100 Hummer Code

1. What are the common symptoms of OBDII code U0100 in a Hummer?

- Common symptoms include the check engine light illuminating, loss of communication with the engine control module, and potential issues with engine performance.

2. What can cause the OBDII code U0100 in a Hummer?

- Possible causes of code U0100 include a faulty engine control module, damaged wiring or connectors, a weak battery or charging system, or software issues.

3. How can I diagnose the OBDII code U0100 in my Hummer?

- Diagnosing code U0100 often involves checking for other related codes, inspecting wiring and connectors for damage, testing the battery and charging system, and using a scan tool to communicate with the engine control module.

4. Can I still drive my Hummer with the U0100 code present?

- It is not recommended to continue driving your Hummer with code U0100 present, as it can lead to potential issues with engine performance and safety. It's best to address the problem promptly.

5. What are some repair tips for fixing the U0100 code in a Hummer?

- Repair tips include checking and repairing any damaged wiring or connectors, ensuring the battery and charging system are in good condition, and potentially reprogramming or replacing the engine control module.

6. How much does it typically cost to repair the U0100 code in a Hummer?

- The cost of repairing code U0100 can vary depending on the underlying cause. Repairs may range from a simple wiring repair to a more involved engine control module replacement, potentially costing hundreds to over a thousand dollars.

7. Is it possible to reset the U0100 code in a Hummer without making repairs?

- While you can clear the code using a scan tool, it is not recommended to reset the code without addressing the underlying issue, as it may lead to recurring problems and potential safety hazards.

8. Can a DIY enthusiast fix the U0100 code in a Hummer?

- Depending on the cause of the code, some DIY enthusiasts may be able to fix code U0100 by inspecting wiring, connectors, and performing basic diagnostic tests. However, more complex issues may require professional assistance.

9. How long does it take to repair the U0100 code in a Hummer?

- The repair time for code U0100 can vary depending on the cause and complexity of the issue. Simple fixes like repairing wiring may take a few hours, while more involved repairs could take a day or more.

10. Are there any preventive measures to avoid the U0100 code in a Hummer?

- To potentially prevent code U0100, it's essential to regularly maintain your Hummer, check for any warning signs of electrical issues, and address any check engine lights promptly to avoid communication problems with the engine control module.