U0074 GMC Code - Control Module Communication Powertrain Expansion CAN Bus Off Malfunction
Quick Answer
The U0074 GMC code indicates a malfunction in the Control Module Communication Powertrain Expansion CAN Bus Off. Common causes include Faulty control module, Wiring or connection issues, Loose connections in the CAN bus network. 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 Faulty control module, Wiring or connection issues, Loose connections in the CAN bus network.
- 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 U0074 GMC Description
The U0074 GMC code indicates a malfunction in the Control Module Communication Powertrain Expansion CAN Bus Off. This means that there is a communication error between the various control modules in the vehicle's powertrain system. The CAN (Controller Area Network) bus is a communication network that allows different modules in the vehicle to exchange information and control various functions. When this communication is disrupted, it can lead to a variety of issues affecting the vehicle's performance.
Common Causes of U0074 GMC
- Faulty control module
- Wiring or connection issues
- Loose connections in the CAN bus network
- Software malfunction
- Electrical interference
Symptoms of U0074 GMC
- Check Engine Light is illuminated
- Rough engine performance
- Difficulty starting the vehicle
- Reduced fuel efficiency
- Transmission shifting issues
How to Fix U0074 GMC
- Diagnosis: The first step in resolving the U0074 code is to perform a thorough diagnosis using a diagnostic scanner to identify the exact cause of the communication error.
- Inspect wiring and connections: Check the wiring harness and connections related to the control modules and the CAN bus for any signs of damage or corrosion. Repair or replace as needed.
- Test control modules: Test the various control modules involved in the powertrain system to determine if any are faulty and need to be replaced.
- Clear codes: Once the issue has been resolved, clear the diagnostic trouble codes and test drive the vehicle to ensure the problem has been fixed.
- Relearn procedures: In some cases, relearn procedures may need to be performed to reset the control modules and ensure proper communication.
Cost to Fix U0074 GMC
The cost of repairing the U0074 code can vary depending on the exact cause of the issue and the labor rates at the auto repair shop. Typically, the repair costs for this issue can range from $200 to $500, including parts and labor. However, it is important to note that the specific diagnosis time and labor rates can vary based on factors such as location, vehicle make and model, and engine type. It is advisable to check with local auto repair shops for a more precise estimate.
Tech Notes for U0074 GMC
- 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.
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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
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 vehicle’s electrical system, ensuring that all connections are secure, and periodically checking for updates for control module software can help prevent this issue.
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