Quick Answer
U0855 means: U0855 indicates a communication failure between vehicle modules.
Can I drive with U0855? Immediate attention is recommended to avoid further issues.
Common Questions
What does U0855 mean and how does it affect my car?
The U0855 code indicates that your vehicle's control modules are having trouble communicating. This can lead to various issues such as erratic vehicle behavior, poor fuel economy, and potential safety risks if critical systems fail to work together. It's important to address this code promptly to ensure your vehicle operates safely and efficiently.
What are the most common causes of U0855 and how much does it cost to fix?
Common causes of U0855 include faulty wiring (60% likely), malfunctioning control modules, and electrical interference. Repair costs can range from $200 for wiring repairs to over $1200 for control module replacements, depending on the severity of the issue.
Can I drive my car with U0855 or should I stop immediately?
It's not advisable to drive your vehicle with U0855. The communication failure could worsen, leading to more severe problems, including stalling or loss of power. If you experience any significant symptoms, it's best to seek professional assistance as soon as possible.
How can I diagnose U0855 myself using GeekOBD APP?
You can use the GeekOBD APP to scan your vehicle for codes and retrieve freeze frame data, providing insight into what may have triggered the U0855 code. Follow the app's prompts to view live data and check for any related codes that may help you pinpoint the issue.
What vehicles are most commonly affected by U0855?
U0855 is frequently reported in 2015-2019 Chevrolet Silverado and GMC Sierra models. Other vehicles may also be affected, but these models have a higher incidence of this specific code due to their complex electronic systems.
How can I prevent U0855 from happening again?
To prevent U0855 from recurring, ensure that you regularly inspect and maintain your vehicle's wiring and connectors. Avoid modifications that could interfere with the electrical systems, and consider having your vehicle's software updated during routine maintenance.
What is U0855?
The diagnostic trouble code (DTC) U0855 indicates a communication problem within the vehicle's network, specifically related to the control modules. This code typically arises when the Powertrain Control Module (PCM) fails to receive or send data from other modules, such as the Transmission Control Module (TCM) or Instrument Cluster. In simpler terms, U0855 signifies that your vehicle's onboard systems are having trouble 'talking' to one another. This can lead to a range of operational issues, including reduced performance, erratic behavior of the vehicle's systems, and even safety concerns if critical systems fail to communicate. For instance, if the engine control module cannot communicate with the transmission control module, you might experience shifting issues or reduced power. Vehicles like the 2015-2019 Chevrolet Silverado and GMC Sierra often report this code, which may also trigger the check engine light. If left unaddressed, the communication breakdown can lead to more severe issues, resulting in costly repairs. Therefore, it's crucial to diagnose and address the root causes promptly to maintain your vehicle's performance and safety.
System: U - Network (Communication, CAN Bus)
Symptoms
Common symptoms when U0855 is present:
- The check engine light may illuminate, often remaining on until the issue is resolved.
- You may experience erratic shifting behavior, such as harsh or delayed shifts while driving, which can compromise safety.
- Fuel economy could decrease significantly, with reports of up to a 20% drop due to inefficient engine management and transmission operation.
- Dashboard warning lights may activate, including indicators for the ABS or traction control systems, signaling broader communication issues.
- In some cases, the vehicle may experience stalling or hesitation during acceleration, indicating a malfunction in the powertrain.
Possible Causes
Most common causes of U0855 (ordered by frequency):
- The most common cause of U0855 is a faulty communication wire or connector, which occurs in approximately 60% of cases. Damage or corrosion in the wiring harness can disrupt signals between modules.
- Another frequent cause is a malfunctioning control module. For instance, if the TCM or PCM is defective, it can fail to communicate properly, affecting vehicle operation.
- Electrical interference, often caused by aftermarket accessories or modifications, can lead to communication issues. It's advisable to ensure all installations are done correctly to prevent such problems.
- Less common but serious causes include software glitches in the control modules. In these cases, a software update may be necessary to resolve the communication failure.
- A rare but possible cause of U0855 is a complete failure of the OBD-II port itself, which can prevent communication between the vehicle and diagnostic tools.
U0855 Repair Costs
Cost Breakdown by Repair Type
Wiring Repair
Repairing damaged wiring or connectors that caused the communication failure.
- Total: $200 - $500
- Success rate: 85%
Control Module Replacement
Replacing a faulty control module that is not communicating properly.
- Total: $600 - $1200
- Success rate: 90%
Software Update
Updating the software of the control modules to fix communication issues.
- Total: $100 - $250
- Success rate: 70%
Money-Saving Tips for U0855
- Start with the most common and least expensive repairs first
- Use GeekOBD APP to confirm diagnosis before replacing expensive parts
- Consider preventive maintenance to avoid future occurrences
- Compare prices for OEM vs aftermarket parts based on your needs
- Address the issue promptly to prevent more expensive secondary damage
Diagnostic Steps
Professional U0855 Diagnosis Process
Follow these systematic steps to accurately diagnose U0855. Each step builds on the previous one to ensure accurate diagnosis.
Step 1: Step 1: Start with a visual inspection of wiring and connectors for signs of damage or corrosion
Step 1: Start with a visual inspection of wiring and connectors for signs of damage or corrosion. Look for loose connections that could disrupt communication (5-10 minutes).
Step 2: Step 2: Use an OBD2 scanner or the GeekOBD APP to check for U0855 and any other related codes, as this will provide context for the issue (10-15 minutes)
Step 2: Use an OBD2 scanner or the GeekOBD APP to check for U0855 and any other related codes, as this will provide context for the issue (10-15 minutes).
Step 3: Step 3: Conduct component testing on the suspected control modules using a multimeter or specialized diagnostic tools to assess their functionality (20-30 minutes)
Step 3: Conduct component testing on the suspected control modules using a multimeter or specialized diagnostic tools to assess their functionality (20-30 minutes).
Step 4: Step 4: Perform a system function test after making repairs to ensure all modules are communicating correctly, then clear the codes from memory (10-15 minutes)
Step 4: Perform a system function test after making repairs to ensure all modules are communicating correctly, then clear the codes from memory (10-15 minutes).
Step 5: Step 5: Finally, conduct a road test to evaluate the vehicle's performance under various conditions, confirming that the issue has been resolved (15-20 minutes)
Step 5: Finally, conduct a road test to evaluate the vehicle's performance under various conditions, confirming that the issue has been resolved (15-20 minutes).
Important Notes
- Always verify the repair with GeekOBD APP after completing diagnostic steps
- Clear codes and test drive to ensure the problem is resolved
- Address underlying causes to prevent code recurrence
Real Repair Case Studies
Case Study 1: Communication Failure in 2017 Chevrolet Silverado
Vehicle: 2017 Chevrolet Silverado 1500, 45,000 miles
Problem: Customer reported the check engine light was on, with harsh shifting and reduced power.
Diagnosis: Diagnostics revealed U0855. A visual inspection showed corrosion in the wiring harness leading to the TCM.
Solution: Repaired the damaged wiring and replaced the TCM due to internal faults.
Cost: $750 (parts: $500 for TCM, $250 for labor)
Result: After the repair, the communication was restored, and the vehicle operated smoothly without further issues.
Case Study 2: Software Update Resolves U0855 in 2018 GMC Sierra
Vehicle: 2018 GMC Sierra 1500, 30,000 miles
Problem: Customer experienced erratic shifts and occasional stalling.
Diagnosis: OBD scan identified U0855. A software update was recommended due to known issues with the module firmware.
Solution: Performed a software update on the PCM and TCM.
Cost: $150 (software update fee)
Result: The update resolved the communication issues, and the vehicle returned to normal operation without further symptoms.