U1000 Communication Area Network (CAN) Lost Communication

mansoorkhan October 25, 2018

U1000 Communication Area Network (CAN) Lost Communication



What does code U1000 mean?

This is a manufacturer specific network code. Specific troubleshooting steps will vary depending on the vehicle.
Modern vehicles use a data bus to allow communication between onboard computers. This data bus is called a communication area network (CAN) and the computers are referred to as modules. A typical late-model vehicle has many modules and they all share their information via the CAN bus. There are dedicated modules for most parts of the vehicle. For example, there’s an engine control module (ECM), transmission (TCM) and brake control module (BCM).


U1000 Possible Causes.?

The cause for this code varies with each vehicle. The second code will identify the defective part or area that the fault has occurred. The code is so specific that the technical service bulletins (TSBs) must be examined not only for the make of vehicle but for the specific model and options present for an accurate assessment.
  1. Controller Area Network (CAN) communication harness is open or  
    shorted
  2. Faulty Engine Control Module (ECM)
  3. Poor harness ground connection.

U1000 Symptoms..?

  • An illuminated check engine light
  • A secondary code specifying a failed module
  • Performance problems ranging from a no-start condition to inoperative HVAC system, depending on which module is unable to communicate
If the U1000 stands alone, no symptoms may be present

When is the code detected?

When ECM is not transmitting or receiving CAN communication signal of OBD (emission-related diagnosis) for 2 seconds or more.


Code U1000 Details

U1000 is a manufacturer specific code. Because of this, the code definition may verysomewhat between vehicles.
Usually, the problem is poor harness ground connection.
There is a service bulletin for the following Nissan models with U1000 code:
– 2002-2006 Nissan Maxima
– 2004-2006 Nissan Titan
– 2004-2006 Nissan Armada
– 2002-2006 Nissan Sentra
– 2005-2006 Nissan Frontier
– 2002-2006 Nissan Altima
– 2005-2006 Nissan Xterra
– 2005-2006 Nissan Pathfinder
– 2004-2006 Nissan Quest
– 2003-2006 Nissan 350Z
– 2003-2006 Nissan Murano
Service bulletin suggests cleaning engine and body harness ground connection to repair the problem. 
– Clean/re-tighten ECM ground connections.
– Clean/re-tighten negative battery cable body connection and battery post connection.
– If needed, clean and ensure good contact between the steering member assembly and the left side instrument stay assembly.

U1000 Code Repair Information

All communications through the CAN bus requires a good ground, continuity without shorting, lack of resistance which would cause a drop in voltage and good components.
  • Access all technical service bulletins (TSB) relating to code U1000 and any additional codes for your particular model and option group.
  • Use the service manual in combination with the TSBs to identify the area or module at fault.
  • Study the method to access the faulty module. Disconnect the module to isolate it from the CAN bus harness and connector.
  • Check the CAN bus harness and connector for shorts or opens using a voltmeter.
  • Follow the directions in the service manual used for determining whether the ECM is at Fault or if the module is to blame.
Read P0011 Nissan Fault Code Problem Solution

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