U1999 – is a generic communication error code indicating a problem with the vehicle’s communication network.
The ODBII code U1999 indicates a generic communication error within the vehicle’s communication network, suggesting a problem with data transmission between modules.
The severity of ODBII code U1999 is generally considered moderate.
Common Causes For: U1996 Vehicle Communication Bus Malfunction
- Faulty wiring or connectors in the communication network.
- Malfunctioning control modules.
- Poor ground connections.
- Interference from aftermarket devices.
- Corroded or damaged pins in connectors.
- Software issues or outdated firmware in control modules.
- Low battery voltage or weak battery.
- Faulty OBD-II port.
Common misdiagnosis for U1999 is a generic communication error code indicating a problem with the vehicle’s communication network.
- Faulty OBDII scanner
- Bad ground connections
- Defective wiring harness
- Malfunctioning ECU (Engine Control Unit)
- Issues with other control modules
- Corrupted software or firmware
- Faulty sensors
- Battery or power supply issues
- Intermittent connection problems
- Incorrectly installed aftermarket accessories
Common Troubleshooting Steps
When dealing with OBD-II code U1999, which indicates a generic communication error in the vehicle’s communication network, there are several common troubleshooting steps you can follow to diagnose and potentially resolve the issue. Here’s a structured approach:
- Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes. U1999 may be accompanied by other codes that can provide more context about the issue.
- Inspect the OBD-II Connector: Ensure that the OBD-II connector is clean and free of corrosion. Check for any bent or damaged pins that could affect communication.
- Examine Wiring and Connectors: Inspect the wiring and connectors associated with the communication network (CAN bus, LIN bus, etc.). Look for signs of damage, fraying, or loose connections.
- Pay special attention to ground connections, as poor grounding can lead to communication issues.
- Check for Short Circuits or Open Circuits: Use a multimeter to check for continuity in the communication lines. Look for any short circuits or open circuits that could disrupt communication.
- Inspect Modules: Identify and inspect the modules that are part of the vehicle’s communication network. This may include the Engine Control Module (ECM), Transmission Control Module (TCM), Body Control Module (BCM), etc.
- Ensure that all modules are functioning properly and are powered on.
- Test Communication: Use a scan tool to test communication with each module. If certain modules are not responding, it may indicate a problem with that specific module or its wiring.
- Check for Software Updates: Verify if there are any software updates available for the vehicle’s modules. Sometimes, communication issues can be resolved with a software update.
- Inspect for Interference: Look for any aftermarket devices or modifications that may interfere with the vehicle’s communication network. This includes alarm systems, stereo systems, or other electronic devices.
- Battery and Power Supply Check: Ensure that the vehicle’s battery is in good condition and that the electrical system is functioning properly. Low voltage can cause communication errors.
- Clear Codes and Test Drive: After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.1
- Consult Technical Service Bulletins (TSBs): Check for any TSBs related to the specific make and model of the vehicle. Manufacturers may have issued guidance on known communication issues.1
- Seek Professional Help: If the issue persists after following these steps, it may be necessary to consult a professional mechanic or technician who specializes in automotive electronics. By following these troubleshooting steps, you can systematically identify and address the underlying issues causing the U1999 code.