Quick Answer
U0256 means: DTC U0256 indicates a communication failure between the powertrain control module and other control modules.
Can I drive with U0256? Immediate diagnosis is recommended to prevent further complications.
Common Questions
What does U0256 mean and how does it affect my car?
DTC U0256 indicates a communication error between your vehicle's control modules. This can lead to issues like engine performance problems, malfunctioning electrical components, and even stalling. Addressing this code is essential to maintain your vehicle's reliability and safety.
What are the most common causes of U0256 and how much does it cost to fix?
Common causes include damaged wiring (60% likelihood), faulty BCM, and software issues. Repair costs can range from $150 for wiring repairs to $800 for BCM replacement, depending on the severity of the issue.
Can I drive my car with U0256 or should I stop immediately?
It is advisable to avoid driving your vehicle until the issue is diagnosed, as it may lead to further damage or unsafe driving conditions.
How can I diagnose U0256 myself using GeekOBD APP?
Using the GeekOBD APP, you can scan for diagnostic trouble codes, view freeze frame data, and check sensor readings to identify potential issues related to U0256. Make sure your device is compatible with the app.
What vehicles are most commonly affected by U0256?
DTC U0256 is frequently found in 2015-2019 Chevrolet and GMC models, such as the Silverado and Sierra, particularly those with complex electrical systems.
How can I prevent U0256 from happening again?
Regularly inspect your vehicle's wiring and electrical connections, keep software updated, and avoid aftermarket installations that could disrupt electrical systems.
What is U0256?
DTC U0256 is a diagnostic trouble code indicating a communication issue between control modules in your vehicle. Specifically, this code signifies that the powertrain control module (PCM) is unable to receive messages from the body control module (BCM) or the transmission control module (TCM). This loss of communication can lead to various malfunctions, including failure of certain electrical components, erratic engine behavior, and issues with transmission operation. In real-world scenarios, drivers might notice that their dashboard warning lights, such as the check engine light, remain illuminated, or they may experience delayed or rough shifting in their automatic transmissions. This code is often seen in popular models like the Chevrolet Silverado and GMC Sierra from 2015 to 2019. Ignoring this code can lead to more severe electrical issues, decreased vehicle performance, and even safety concerns while driving, as certain systems may fail to operate as intended. Therefore, prompt diagnosis and repair are crucial to ensure the proper functioning of your vehicle’s systems.
System: U - Network (Communication, CAN Bus)
Symptoms
Common symptoms when U0256 is present:
- Check engine light stays on constantly, indicating a communication failure.
- Delayed or harsh shifting in automatic transmissions, leading to a rough driving experience.
- Inconsistent operation of electrical components such as windows or lights, which may fail to respond as expected.
- Unexpected engine stalling or hesitation during acceleration, making it unsafe to drive.
- Battery drain issues due to malfunctioning modules that remain active even when the vehicle is off.
Possible Causes
Most common causes of U0256 (ordered by frequency):
- The most common cause of U0256 is damaged wiring or connectors between the PCM and BCM, which occurs in about 60% of cases. Look for frayed wires or corrosion.
- Another common cause is a malfunctioning BCM itself. If the BCM is not operating correctly, it can fail to send or receive signals properly.
- In some cases, programming issues or software glitches in the control modules can lead to U0256. Keeping firmware updated can prevent this.
- Less common, but serious, is a failed PCM that does not communicate with other modules. This could require a costly replacement.
- A rare cause includes interference from aftermarket accessories that disrupt the vehicle's electrical systems.
U0256 Repair Costs
Cost Breakdown by Repair Type
Wiring Repair
Repairing or replacing damaged wiring or connectors between the PCM and BCM.
- Total: $150 - $400
- Success rate: 85%
BCM Replacement
Replacing a faulty body control module if it fails to communicate.
- Total: $400 - $800
- Success rate: 90%
PCM Reprogramming
Reprogramming the powertrain control module to fix software issues.
- Total: $100 - $300
- Success rate: 75%
Money-Saving Tips for U0256
- 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 U0256 Diagnosis Process
Follow these systematic steps to accurately diagnose U0256. Each step builds on the previous one to ensure accurate diagnosis.
Step 1: Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion (5-10 minutes)
Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion (5-10 minutes).
Step 2: Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context (10-15 minutes)
Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context (10-15 minutes).
Step 3: Step 3: Component testing - Use multimeter or specific diagnostic tools to test suspected components, such as the PCM and BCM (20-30 minutes)
Step 3: Component testing - Use multimeter or specific diagnostic tools to test suspected components, such as the PCM and BCM (20-30 minutes).
Step 4: Step 4: System function test - Verify proper operation after repairs and clear codes (10-15 minutes)
Step 4: System function test - Verify proper operation after repairs and clear codes (10-15 minutes).
Step 5: Step 5: Road test verification - Drive vehicle under various conditions to confirm repair success (15-20 minutes)
Step 5: Road test verification - Drive vehicle under various conditions to confirm repair success (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: Wiring Repair on 2017 Chevrolet Silverado
Vehicle: 2017 Chevrolet Silverado 1500, 50,000 miles
Problem: Customer experienced persistent check engine light and intermittent electrical failures.
Diagnosis: Visual inspection revealed damaged wiring between the PCM and BCM.
Solution: Repaired and replaced the damaged wiring harness.
Cost: $250 for parts and labor.
Result: Customer reported no further issues post-repair, and the check engine light remained off.
Case Study 2: BCM Replacement on 2018 GMC Sierra
Vehicle: 2018 GMC Sierra 2500HD, 30,000 miles
Problem: Vehicle displayed U0256 code with erratic behavior in lights and windows.
Diagnosis: Diagnostic tests confirmed a faulty BCM.
Solution: Replaced the BCM with a new unit and reprogrammed it.
Cost: $600 for parts and labor.
Result: All electrical functions returned to normal, and no further codes appeared.