U0059 Code: High-Speed CAN Communication Bus Performance Problem
Short Description:
U0059 indicates that one or more control modules have detected abnormal performance on the High-Speed Controller Area Network (CAN) Bus. Communication remains possible but is degraded due to electrical or network-related faults.
What Does U0059 Mean?
The U0059 Diagnostic Trouble Code (DTC) is stored when the High-Speed CAN Bus fails to maintain normal communication performance. Unlike complete communication loss codes, U0059 generally indicates unstable data transmission caused by electrical interference, excessive circuit resistance, poor grounding, damaged wiring, connector corrosion, or an internally faulty control module.
The High-Speed CAN Bus allows continuous communication between critical vehicle systems including the Engine Control Module (ECM), Transmission Control Module (TCM), Anti-lock Brake System (ABS), Body Control Module (BCM), Electric Power Steering (EPS), Instrument Cluster, and other electronic modules.
High-Speed CAN Bus Overview
The High-Speed CAN Bus uses two differential communication wires: CAN High (CAN-H) and CAN Low (CAN-L). These opposite voltage signals improve resistance to electrical noise while providing fast and reliable communication between control modules.
Damage to either communication wire, poor terminal contact, low battery voltage, weak ground connections, failed termination resistors, or an internally malfunctioning module may reduce communication quality and trigger U0059.
Common Symptoms
| Symptom | Description |
|---|---|
| Check Engine Light | Communication fault detected. |
| ABS / ESC Warning | Brake or stability warning lamps may illuminate. |
| Intermittent Module Communication | Some modules may disconnect randomly. |
| Electronic System Malfunctions | Various vehicle systems may operate abnormally. |
Common Causes
| Cause | Explanation |
|---|---|
| Damaged CAN Wiring | Open circuit, short circuit, or high resistance. |
| Loose or Corroded Connectors | Poor terminal contact interrupts communication. |
| Weak Battery | Low voltage reduces CAN Bus stability. |
| Poor Ground Connection | Ground faults create unstable communication signals. |
| Faulty Control Module | A defective module can interfere with the CAN network. |
High-Speed CAN Bus Network Diagram
The diagram below shows a simplified High-Speed CAN Bus network connecting major vehicle control modules.
Diagnosis Procedure
Begin by performing a complete network scan using a professional diagnostic scanner. Record all stored communication DTCs before clearing any codes. Check battery voltage, charging system output, CAN Bus wiring, connectors, ground circuits, and network resistance before replacing any control module.
Step 1: Scan All Control Modules
Communication faults often affect multiple modules simultaneously. Any module that is offline or reporting intermittent communication can help identify the source of the network problem.
| Related Code | Description |
|---|---|
| U0100 | Lost Communication With ECM/PCM |
| U0121 | Lost Communication With ABS Module |
| U0140 | Lost Communication With BCM |
| U0155 | Lost Communication With Instrument Cluster |
Typical Live Data
The following values represent typical High-Speed CAN Bus measurements. Always compare readings with the manufacturer's specifications for the vehicle being serviced.
| Parameter | Typical Value | Fault Indication |
|---|---|---|
| CAN High (CAN-H) | 2.5–3.5 V | Fixed or Unstable Voltage |
| CAN Low (CAN-L) | 2.5–1.5 V | Fixed or Unstable Voltage |
| Bus Resistance | ≈60 Ω | 0 Ω / 120 Ω / Open |
| Module Status | Online | Offline / Intermittent |
Oscilloscope Waveform Analysis
A dual-channel oscilloscope provides the fastest method for evaluating CAN Bus signal quality. CAN-H and CAN-L should produce clean mirrored waveforms during normal network communication.
Normal Signal
Distorted Signal
No Communication
Estimated Repair Cost
| Repair | Estimated Cost |
|---|---|
| Repair CAN Wiring | $50–300 |
| Replace Connector | $30–150 |
| Module Programming | $100–400 |
| Replace Control Module | $300–1,500+ |
Severity Level
Severity: High
U0059 is considered a high-severity communication code because unstable CAN Bus performance can affect multiple safety and powertrain systems, leading to intermittent faults and reduced vehicle reliability.
Common Repair Mistakes
Avoid replacing electronic control modules before checking battery voltage, charging system performance, CAN wiring, connectors, grounds, and network resistance. Most U0059 faults are caused by electrical problems rather than failed modules.
Recommended Diagnostic Tools
Recommended tools include a professional full-system scan tool, digital multimeter, dual-channel oscilloscope, and manufacturer wiring diagrams for accurate High-Speed CAN Bus diagnosis.
Frequently Asked Questions (FAQ)
Can I drive with the U0059 code?
In many cases, yes. However, because U0059 indicates degraded High-Speed CAN Bus performance, important systems such as the engine, transmission, ABS, electronic stability control, and power steering may operate intermittently or unpredictably. The vehicle should be diagnosed as soon as possible.
Can a weak battery cause U0059?
Yes. A weak battery, poor charging system performance, or unstable system voltage can reduce CAN Bus communication quality and trigger U0059. Battery condition and charging voltage should always be checked before replacing electronic modules.
Can damaged CAN wiring trigger U0059?
Yes. Damaged wiring, loose connectors, corrosion, high resistance, open circuits, or short circuits affecting CAN High or CAN Low are among the most common causes of U0059.
What is the normal CAN Bus resistance?
With the ignition switched OFF, resistance measured between CAN High and CAN Low is typically about 60 Ω. Measurements near 120 Ω, 0 Ω, or an open circuit usually indicate a network fault. Always compare readings with the manufacturer's specifications.
Can a faulty control module cause U0059?
Yes. An internally defective control module can overload or interfere with the CAN Bus, causing unstable communication and triggering U0059. However, wiring faults, connector problems, poor grounds, and battery issues are considerably more common than module failures.
Conclusion
The U0059 diagnostic trouble code indicates degraded performance of the High-Speed CAN Bus communication network rather than failure of a single sensor or actuator. Accurate diagnosis should include checking battery and charging system voltage, CAN Bus resistance, wiring continuity, connector condition, module power and ground circuits, scan tool live data, and oscilloscope waveforms. Following a systematic diagnostic process helps identify the root cause while avoiding unnecessary replacement of expensive control modules.
Comments
Post a Comment