AutoCodes – GMC – U0074 GMC

U0074 GMC Code - Control Module Communication Powertrain Expansion CAN Bus Off Malfunction

Quick Answer

The devices connected to the chassis high-speed General Motor Local Area Network (GMLAN) serial data circuits monitor for serial data communications during normal vehicle operation. Common causes include Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s), Check for more codes, Faulty Control Module. 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: U0074 GMC indicates Control Module Communication Powertrain Expansion CAN Bus Off Malfunction.
Common causes: Common causes include Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s), Check for more codes, Faulty Control Module.
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 5,048

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 Apr 14, 2023

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code U0074 GMC Description

The devices connected to the chassis 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 devices when the ignition switch is in any position other than OFF. The chassis high-speed GMLAN serial data bus uses terminating resistors that are in parallel with the chassis high-speed GMLAN (+) and (-) circuits. The Diagnostic Trouble Code (DTC) will be set when a supervised periodic message that includes the transmitter device availability has not been received for more than 450 ms.

OBDII Code U0074 GMC - Control Module Communication Powertrain Expansion CAN Bus Off Malfunction - AutoCodes.com — U0074 GMC Code - Control Module Communication Powertrain Expansion CAN Bus Off Malfunction

What does this mean?

What are the Possible Causes of the DTC U0074 GMC?

Diagnosis of this Diagnostic Trouble Code (DTC) is accomplished via the vehicle symptom(s)
Check for more codes
Faulty Control Module
Control Module harness is open or shorted
Control Module circuit poor electrical connection

How to Fix the DTC U0074 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 does this mean?

Code Tech Notes

There is a Factory Service Bulletin for the following GMC Models:

- 2014-2018 GMC Sierra
- 2015-2018 GMC Yukon
- 2015-2018 GMC Yukon XL

If the Diagnostic Trouble Codes (DTC) P2635, U0074, and/or U18A2 are set, it may be found that the actual fuel pressure (low-pressure system) will be reading substantially higher than desired fuel pressure, in this case, the cause of the problem is a loss of communication between Engine Control Module (ECM) and Fuel Pump Control Module (FPCM).

- Diagnose for any communication DTCs set (U0074 would take priority over U18A2 if both set) before addressing DTC P2635.
- If DTC P2635 is not resolved by correcting the communication DTCs, only then should diagnose the DTC P2635.
- It has been found that a communication issue between the FPCM and ECM can potentially induce DTC P2635 and result in a pressure differential between actual and desired fuel system pressures.
- If the actual fuel pressure is substantially higher than desired (10 psi / 70 kPa or more), replacement of the fuel pump control module or fuel system components typically will not resolve this issue.
- If the actual fuel pressure is substantially lower than desired (10 psi / 70 kPa or more), this Factory Service Bulletin would NOT apply. It would be recommended to diagnose low actual fuel pressure.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the U0074 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.

Need more information about the U0074 GMC code?

Need more information on how to fix the U0074 GMC code? Get Access to Factory Service Manuals

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Information for Specific GMC Models

U0074 2014 GMC Sierra — Control Module Communication Powertrain Expansion CAN Bus Off Malfunction
U0074 2015 GMC Sierra — Control Module Communication Powertrain Expansion CAN Bus Off Malfunction
U0074 2016 GMC Sierra — Control Module Communication Powertrain Expansion CAN Bus Off Malfunction
U0074 2017 GMC Sierra — Control Module Communication Powertrain Expansion CAN Bus Off Malfunction
U0074 2018 GMC Sierra — Control Module Communication Powertrain Expansion CAN Bus Off Malfunction

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 U0074 GMC Code

1. What does the OBDII code U0074 on a GMC indicate?

The U0074 code signifies a communication issue on the Powertrain Expansion CAN Bus, specifically indicating that the bus is off, which means the control module is not communicating properly with other parts of the vehicle's network.

2. What are common symptoms of the U0074 code in a GMC?

Symptoms include the check engine light turning on, reduced vehicle performance, transmission shifting issues, and in some cases, the engine may not start or the vehicle may enter a limp mode.

3. What can cause the U0074 code to appear on a GMC vehicle?

Potential causes include faulty or damaged wiring, bad connections, a malfunctioning control module, or issues with the CAN bus itself such as a short or open in the communication lines.

4. How can I diagnose the U0074 code on my GMC?

Diagnosis involves using a scan tool to check for communication faults, inspecting the wiring and connectors for damage or corrosion, and testing the function and output of the relevant control modules.

5. What steps are involved in repairing a U0074 code on a GMC?

Repair steps might include replacing or repairing damaged wiring, tightening loose connections, replacing faulty control modules, or resetting the vehicle's network settings.

6. Is it safe to drive a GMC with the U0074 code?

Driving with this code is not recommended as it can lead to unpredictable vehicle behavior and potentially safety-critical systems failing, such as the engine or braking system.

7. How much does it typically cost to fix the U0074 code in a GMC?

Costs can vary widely depending on the root cause. Simple fixes like reconnecting a loose wire might be inexpensive, whereas replacing a control module could cost several hundred dollars.

8. Can a U0074 code cause a GMC to fail emissions testing?

Yes, a U0074 code can cause an emissions test failure because the vehicle's control modules may not operate efficiently, leading to increased emissions.

9. What tools are required to diagnose the U0074 code on a GMC?

Tools needed include a professional OBD-II scanner, digital multimeter, and possibly an oscilloscope to analyze the signals on the CAN bus lines.

10. How can I prevent the U0074 code from happening in my GMC?

Regular maintenance of the vehicleâ€™s electrical system, ensuring that all connections are secure, and periodically checking for updates for control module software can help prevent this issue.