U0009 - HIGH-SPEED CAN COMMUNICATION BUS (-) SHORTED TO BUS (+)

The control modules are connected to a complex communication network called CAN-Bus (Controller Area Network). It is through this network that the working parameters and various information are exchanged between the modules. Each controller has stored messages, which are necessary to send at the time of starting the data transmission, and through which you can determine the availability of the transmitter module.

The communication networks are HS-CAN (High-Speed Controller Area Network), MS-CAN (Medium Speed Controller Area Network), and the I-CAN (Infotainment Controller Area Network). Diagnostic code U0009 OBDII will be set when the High-Speed CAN Bus has a malfunction caused by a short circuit.

• Check Engine lamp illuminated.
• Other fault codes may be present.
• The car has difficulty starting.
• There are malfunctions in the acceleration.
• The control modules start to fail, as they cannot send their data to each other.
• There are errors in the ignition.
• The alarm is abruptly activated.
• The engine suddenly shuts down.

The U0009 OBD2 fault code is stored because of the following problems:

• A control module may have wiring deficiencies.
• There may be damage to a controller.
• The supply on the high-speed CAN bus line may be blocked.
• The ground may be insufficient.
• The alternator could be faulty.
• Wiring, fuses, connections, and relays may be defective.

To correct the DTC U0009 OBDII code, consider the following advice:

• As a first step consult the Technical Service Bulletins.
• Using a scanner you should verify if the DTC U0009 is configured conjunctly with other codes that may refer to a problem with a specific controller. If this is your case, diagnose the codes taking into account the order in which they are displayed.
• Check that there is no damage to the wiring and connections related to the HS-CAN (High-Speed Controller Area Network). If one of these has deficiencies caused by burns or wear, proceed with the corresponding adjustments.
• Shake the electrical components lightly and observe if any faults occur during this test.
• Observe which devices are compromising the electrical system.
• Progressively shake each installation monitoring the system for the recurring event of the fault. This test is an indicator of the possible existence of a maladjusted installation.
• If the terminals are exposed to steam, oxidation can affect the connectors. This problem can be remedied with an electrical parts cleaner; if this is not helpful, the affected part should be replaced.
• The electrical continuity of the installation should be tested and verified if it is short somewhere, this is done with a digital multimeter or tester.