Introduction:

The U0059 diagnostic trouble code (DTC) signals a problem within a vehicle's communication network, specifically indicating a "High" voltage condition on the Data Communication Bus D (+) circuit. This bus is crucial for various electronic control units (ECUs) to communicate and share information. A malfunction in this communication network can lead to a range of issues, impacting vehicle performance, safety systems, and overall functionality.

Table: U0059 Vehicle Communication Bus D (+) High - Details and Solutions

Category Description Potential Solutions
Definition Vehicle Communication Bus D (+) High. This indicates that the voltage on the "D" communication bus positive (+) wire is higher than expected or specified by the vehicle manufacturer. "Bus D" refers to a specific communication network within the vehicle, often related to chassis or body control systems. The "+" designates the positive wire in the differential communication pair. None needed if just understanding the code.
Common Symptoms - Malfunction Indicator Lamp (MIL) illuminated. - Erratic behavior of various vehicle systems (e.g., ABS, traction control, power windows, door locks). - Communication errors between ECUs. - Loss of functionality in certain vehicle components or systems. - Stored DTCs in multiple ECUs related to communication errors. - Potential inability to start the vehicle (rare, but possible if the bus is critical to engine management). - Instrument panel warnings or error messages. - Reduced performance in systems reliant on data from the bus. Observe and document symptoms.
Possible Causes - Faulty ECU: An ECU connected to Bus D could be malfunctioning and sending an abnormally high voltage signal onto the bus. - Wiring Issues: Short to voltage in the wiring harness connected to the Bus D (+) wire. Corrosion, damage, or loose connections in the wiring harness. - Failed Terminator Resistor: The CAN bus uses terminator resistors at each end of the bus to maintain signal integrity. A faulty resistor can cause voltage imbalances. - Aftermarket Accessories: Poorly installed or malfunctioning aftermarket accessories connected to the vehicle's electrical system, interfering with the CAN bus. - Software Glitches: Rare, but a software glitch within an ECU could potentially cause communication errors. - Water Intrusion: Water damage to connectors or ECUs can cause shorts and voltage issues. - Physical Damage: Damage to the wiring harness from accidents or repairs. - Inspect wiring harness for damage, shorts, or corrosion. - Check ECU connectors for proper connection and corrosion. - Disconnect aftermarket accessories one by one to see if the issue resolves. - Test terminator resistor values. - Use a scan tool to monitor CAN bus voltage. - Perform a wiggle test on the wiring harness to see if the code appears or disappears. - Inspect for water intrusion in connectors and ECUs. - Consult the vehicle's wiring diagram for specific component locations and wiring routes. - Inspect the battery voltage and charging system.
Diagnostic Steps 1. Scan for Codes: Use a professional-grade scan tool to read all stored DTCs in all ECUs. Note all codes present, as they may provide clues. 2. Visual Inspection: Thoroughly inspect the wiring harness and connectors associated with Bus D. Look for signs of damage, corrosion, or loose connections. Pay close attention to areas where the harness may rub against the vehicle's chassis. 3. CAN Bus Voltage Testing: Use a multimeter or oscilloscope to measure the voltage on the Bus D (+) and (-) wires. Compare the readings to the manufacturer's specifications. A significant deviation from the specified voltage range indicates a problem. 4. Component Isolation: If a specific ECU is suspected, disconnect it from the Bus D and re-scan for codes. If the U0059 code disappears, the disconnected ECU is likely the culprit. 5. Wiring Harness Testing: Use a multimeter to check the continuity and resistance of the Bus D (+) and (-) wires. A short to ground or a break in the wire will affect the bus voltage. 6. Terminator Resistor Testing: Locate the terminator resistors at each end of the Bus D and use a multimeter to measure their resistance. The resistance should be approximately 120 ohms. An open or shorted resistor can disrupt communication. 7. Oscilloscope Waveform Analysis: Use an oscilloscope to analyze the CAN bus waveform. A distorted or missing waveform indicates a problem with the bus. 8. Consult Vehicle-Specific Information: Refer to the vehicle's service manual or wiring diagram for specific information about the Bus D, including component locations, wiring routes, and voltage specifications. 9. Module Communication Test: Use a scan tool to perform a module communication test to see which modules are communicating on the bus and which are not. Follow each step systematically.
Tools Required - Professional-grade scan tool with CAN bus diagnostic capabilities. - Multimeter. - Oscilloscope (optional, but highly recommended for advanced diagnostics). - Wiring diagram for the specific vehicle. - Connector cleaner. - Terminal pin extractor. - Basic hand tools (e.g., screwdrivers, pliers, wire strippers). - Test lights. Gather all necessary tools before starting the diagnostic process.
Related DTCs - U0001: High Speed CAN Communication Bus. - U0100: Lost Communication with ECM/PCM. - U0121: Lost Communication with ABS Control Module. - U0155: Lost Communication with Instrument Panel Cluster (IPC). - Other U-codes related to lost communication with specific modules. - Any code related to a module connected to Bus D. - B-codes (Body codes) related to components controlled by modules on Bus D. Note these codes, as they can provide additional diagnostic information.
Severity Moderate to High. The severity depends on the specific systems affected by the communication failure. Loss of critical systems like ABS or traction control can pose a safety risk. Communication failures can also lead to vehicle drivability problems and inconvenience. Address the issue promptly to avoid potential safety risks and further damage.
Repair Costs Variable, depending on the cause. Simple wiring repairs may be relatively inexpensive, while replacing a faulty ECU can be costly. Diagnostic labor costs can also add to the overall expense. Accurate diagnosis is crucial to avoid unnecessary repairs. Obtain multiple quotes from reputable repair shops.
Preventative Measures - Regularly inspect wiring harnesses for damage or corrosion. - Ensure proper installation of aftermarket accessories. - Protect the vehicle's electrical system from water intrusion. - Address any electrical issues promptly to prevent further damage. - Avoid overloading the vehicle's electrical system. - Ensure proper battery maintenance. Implement these measures to minimize the risk of future communication bus problems.

Detailed Explanations:

Definition: The U0059 code signifies that the voltage on the Data Communication Bus D (+) wire is excessively high. This bus is a network that allows different ECUs within the vehicle to communicate with each other. The "+" symbol indicates the positive wire in the differential communication pair. This high voltage condition disrupts the normal communication flow.

Common Symptoms: Several symptoms can arise due to a U0059 code. The most common is the illumination of the Malfunction Indicator Lamp (MIL). Erratic behavior in various vehicle systems like ABS, traction control, power windows, and door locks can also occur. Communication errors between ECUs, loss of functionality in certain components, stored DTCs in multiple ECUs, and even an inability to start the vehicle (though rare) are also possibilities. Instrument panel warnings and reduced performance in systems relying on data from the bus are other potential indicators.

Possible Causes: The root cause of a U0059 code can vary. A faulty ECU connected to Bus D could be sending an abnormally high voltage signal. Wiring issues such as a short to voltage, corrosion, damage, or loose connections are common culprits. A failed terminator resistor, which helps maintain signal integrity, can also cause voltage imbalances. Poorly installed aftermarket accessories interfering with the CAN bus, rare software glitches within an ECU, water intrusion into connectors or ECUs, and physical damage to the wiring harness are also potential causes.

Diagnostic Steps: A systematic approach is crucial for diagnosing a U0059 code. Start by scanning for all stored DTCs using a professional-grade scan tool. Perform a thorough visual inspection of the wiring harness and connectors associated with Bus D, looking for damage, corrosion, or loose connections. Use a multimeter or oscilloscope to measure the voltage on the Bus D (+) and (-) wires, comparing the readings to the manufacturer's specifications. If a specific ECU is suspected, disconnect it and re-scan for codes. Test the continuity and resistance of the Bus D wires using a multimeter. Locate and test the terminator resistors. Use an oscilloscope to analyze the CAN bus waveform. Consult the vehicle's service manual for specific information. Finally, perform a module communication test using a scan tool.

Tools Required: Diagnosing a U0059 code requires specific tools. A professional-grade scan tool with CAN bus diagnostic capabilities is essential. A multimeter is needed for voltage and resistance measurements. An oscilloscope is highly recommended for advanced diagnostics and waveform analysis. A wiring diagram for the specific vehicle is crucial. Connector cleaner, terminal pin extractors, basic hand tools, and test lights are also helpful.

Related DTCs: The U0059 code often appears alongside other related DTCs. These include U0001 (High Speed CAN Communication Bus), U0100 (Lost Communication with ECM/PCM), U0121 (Lost Communication with ABS Control Module), U0155 (Lost Communication with Instrument Panel Cluster (IPC)), other U-codes related to lost communication with specific modules, B-codes related to components controlled by modules on Bus D. Noting these codes can provide valuable diagnostic information.

Severity: The severity of a U0059 code ranges from moderate to high. The specific impact depends on the systems affected by the communication failure. Loss of critical systems like ABS or traction control poses a significant safety risk. Communication failures can also lead to vehicle drivability problems and general inconvenience.

Repair Costs: Repair costs for a U0059 code are variable. Simple wiring repairs might be relatively inexpensive, while replacing a faulty ECU can be costly. Diagnostic labor costs can also contribute to the overall expense. Accurate diagnosis is paramount to avoid unnecessary repairs. Obtaining multiple quotes from reputable repair shops is recommended.

Preventative Measures: Several preventative measures can help minimize the risk of future communication bus problems. Regularly inspect wiring harnesses for damage or corrosion. Ensure proper installation of aftermarket accessories. Protect the vehicle's electrical system from water intrusion. Address any electrical issues promptly to prevent further damage. Avoid overloading the vehicle's electrical system and ensure proper battery maintenance.

Frequently Asked Questions:

  • What does the U0059 code mean? It signifies that the voltage on the Data Communication Bus D (+) wire is higher than expected, disrupting communication between ECUs.

  • Can I drive my car with a U0059 code? It's generally not recommended, especially if critical systems like ABS or traction control are affected, as it could be a safety risk.

  • How do I fix a U0059 code? The fix depends on the cause and involves diagnosing the issue, which may include inspecting wiring, testing ECUs, and checking terminator resistors.

  • Is the U0059 code serious? Yes, it can be serious, particularly if it affects safety-related systems. Prompt diagnosis and repair are recommended.

  • Can a bad battery cause a U0059 code? Yes, a weak or failing battery can cause voltage fluctuations and communication errors on the CAN bus.

Conclusion:

The U0059 code signals a critical issue within the vehicle's communication network, requiring a systematic diagnostic approach to identify and resolve the underlying cause. Addressing this code promptly is crucial to ensure the proper functioning of various vehicle systems and maintain safety.