U0073 Error Code

The U0073 error code in Ford vehicles signifies a problem with the Control Module Communication Bus, commonly the Controller Area Network (CAN). When this code appears, it indicates a communication malfunction, often due to a problem within the network, which is vital for data exchange between control modules like the Engine Control Module (ECM), Transmission Control Module (TCM), and Anti-lock Brake System (ABS). Since these systems are interconnected, any disruption can affect performance and safety.

Issue Description

The U0073 error code is defined as “Control Module Communication Bus ‘A’ Off”. This code signals an issue within the CAN bus ‘A’ network, commonly used for high-speed communication between crucial modules. Ford vehicles utilize the CAN system to enable real-time data exchange between modules. When a U0073 code appears, it usually points to a disconnection or interruption in the communication line, which may be caused by a wiring issue, faulty modules, or power-related problems.

The CAN system operates on two lines, CAN ‘A’ and CAN ‘B,’ for high-speed and low-speed communications, respectively. The U0073 code specifically points to an issue in the CAN ‘A’ (high-speed) bus, which can lead to disrupted communication between high-priority modules.

Ford U0073 Error Code

Symptoms

When the U0073 code appears, symptoms may vary depending on which control modules are affected by the communication breakdown. Common signs associated with the U0073 code include:

  • Illuminated Warning Lights: Multiple warning lights may illuminate, such as the Check Engine Light (CEL), ABS, or stability control light.
  • Malfunctioning Systems: Key systems such as the ABS, traction control, or power steering may exhibit malfunctions or reduced functionality.
  • Instrument Cluster Issues: The instrument cluster may show erratic behavior or a lack of response in specific gauges and indicators.
  • Performance Issues: The engine or transmission may operate irregularly, sometimes entering “limp mode” to protect against damage.
  • Reduced or No Response from Diagnostic Tools: Diagnostic scanners may struggle to connect to some modules, making it challenging to retrieve or clear codes.

Causes

The U0073 error code can result from various issues, often involving the CAN bus wiring or components within the high-speed CAN network. Common causes include:

  • Damaged or Corroded CAN Wiring: Frayed or corroded wiring in the CAN bus can prevent the signal from reaching various control modules.
  • Faulty Control Module: A malfunctioning ECM, TCM, or Body Control Module (BCM) can lead to communication disruptions within the CAN network.
  • Electrical Short or Open Circuit: Short circuits or open circuits within the CAN bus wiring are common culprits, leading to complete or partial disconnection between modules.
  • Power Supply or Grounding Issues: Problems with the battery, charging system, or grounding can cause a voltage drop, affecting the CAN system’s performance.
  • Blown Fuse or Faulty Relay: A blown fuse or defective relay associated with the CAN network may prevent communication between modules, triggering the U0073 code.

Diagnosing

Diagnosing the U0073 code requires a step-by-step approach focused on verifying the CAN bus wiring and ensuring that each module in the network is functional. Here’s a structured guide for diagnosing this code:

  • Scan for Trouble Codes: Use an OBD-II scanner capable of reading CAN codes to verify the U0073 code. Check for any other accompanying error codes, as they may point to the specific module or network section causing the issue.
  • Inspect CAN Bus Wiring and Connectors: Visually examine the CAN bus wiring and connectors for signs of wear, corrosion, or disconnection. Pay attention to areas prone to moisture or damage from heat and vibration.
  • Check Related Fuses and Relays: Inspect fuses and relays related to the CAN network. Replace any blown fuses or malfunctioning relays and test the network again to see if the issue is resolved.
  • Test Battery Voltage and Ground Connections: Use a multimeter to measure the battery voltage and inspect ground points associated with the CAN network. Inadequate voltage or poor grounding can disrupt CAN communication.
  • Use Diagnostic Tools to Test Module Communication: Using a diagnostic scanner, try connecting to each module individually to identify any unresponsive module(s) that may be causing the U0073 code.
  • Check for Short or Open Circuits: Measure the voltage and resistance on the CAN high and CAN low circuits to identify any shorted or open circuits within the wiring. Addressing these wiring faults may clear the U0073 code.

Solutions

Once the specific issue has been identified, the U0073 error can typically be resolved with targeted repairs or replacements. Below are common solutions based on identified causes.

  • Repair or Replace Damaged Wiring
    • Repair or Replace Frayed Wiring: If there are signs of damaged or corroded wiring, repair or replace the affected sections. This is essential to re-establishing uninterrupted CAN communication.
    • Protect and Insulate Wiring: After repairs, protect the wiring with insulation to prevent future damage, especially in areas near heat or moisture.
  • Replace or Repair Faulty Control Module
    • Replace Defective Modules: If a particular module, such as the ECM, TCM, or BCM, is malfunctioning, replacing it may restore the CAN network’s functionality. Ensure the replacement module is programmed to communicate with the network.
    • Software Reprogramming: Some communication issues may be resolved with a software update or reprogramming at a Ford dealership or authorized repair center.
  • Fix Electrical Shorts or Open Circuits
    • Repair Short Circuits: If a short circuit is found within the CAN bus wiring, fix or replace the affected wires to prevent further disruption.
    • Correct Open Circuits: If there’s an open circuit within the CAN wiring, trace and repair the gap to re-establish continuity.
  • Check and Maintain Power Supply
    • Recharge or Replace the Battery: Ensure the battery is fully charged and capable of supporting the CAN network. Replace it if needed to prevent voltage drops that could interfere with network communication.
    • Inspect the Alternator and Charging System: A properly functioning charging system helps prevent low voltage issues that may affect the CAN system.
  • Replace Blown Fuses and Faulty Relays
    • Replace Faulty Fuses and Relays: Replace any damaged fuses or relays linked to the CAN system. After replacement, clear the U0073 code and test to see if normal operation resumes.

Preventive Measures

While some CAN communication errors are hard to predict, certain preventative steps can help minimize the risk of a U0073 code in Ford vehicles:

  • Regular Inspection of CAN Wiring and Connectors: Periodically check the CAN wiring for any signs of wear, corrosion, or looseness to address potential issues early.
  • Protect CAN Wiring in High-Risk Areas: Ensure that wiring is insulated from environmental hazards like moisture, high temperatures, and abrasion to reduce damage risk.
  • Maintain a Healthy Battery and Charging System: A fully charged, healthy battery and a reliable charging system help maintain stable voltage levels across the CAN network, reducing the likelihood of communication errors.
  • Use Quality Replacement Parts: When replacing fuses, relays, or control modules, opt for high-quality, Ford-compatible parts to enhance system reliability.
  • Stay Updated with Software Updates: Ensure control modules are updated with the latest software, as this can resolve certain network issues. Authorized Ford service centers can check for available software updates.

Ford Error Codes

  • P0401 Error Code

    P0401 Error Code

    The P0401 error code indicates a problem with the EGR system, which is crucial for controlling emissions.

  • P0420 Error Code

    P0420 Error Code

    The P0420 code indicate significant issues related to the catalytic converter and emissions system.

  • P0707 Error Code

    P0707 Error Code

    The P0707 error code is often caused by a faulty transmission range sensor or issues with its wiring and electrical connections.

  • P0741 Error Code

    P0741 Error Code

    The P0741 error code in Ford vehicles is primarily related to issues with the torque converter clutch or its control circuit.