U1000 Communications Failure OBD-II Trouble Code
U1000: Cannot Communicate with TCM / Class 2 Communications Failure OBD-II Trouble Code
U1000 Possible Causes
- Controller Area Network (CAN) communication harness is open or shorted
- Faulty Engine Control Module (ECM)
- Poor harness ground connection.
How Serious is the Code?
The severity of a U1000 diagnostic trouble code largely depends on the vehicle. The issue stems from a CAN bus (controller area network) fault within the network of wires and modules that allow the ECU to control all of the components on the vehicle. Needless to say, a trained mechanic will need to inspect the vehicle to determine the cause of this OBD2 code.
Symptoms of a U1000 include:
- A particular system in the car may not work
- Engine stalling
- Poor engine performance
- The engine will not start
How to Diagnose the Code?
The first step to diagnosing a U1000 OBDII trouble code, is to check all of the manufacturer’s technical service bulletins (TSB) to see if there’s any known cause and solution for these transmission problems. If no TSB’s are found, then the wiring and connectors along the CAN bus harness will need to be checked for signs of damage and corrosion. All of the ground connections will need to be checked too. The TCM and ECU will also need to be checked.
What Repairs Will Fix U1000?
- Repair damaged wiring, connectors and ground connections
- Replace ECU
- Replace TCM