U1000high severityNetwork
CAN Communication System Malfunction
on 1993-2001 Subaru Impreza 2.2L H4 · AWD
What this code means
The CAN bus network has a communication fault preventing modules from exchanging data properly, similar to generic P-code U0001. This can disrupt multiple systems that rely on shared data.
Symptoms
- Multiple warning lights on
- Erratic gauge or system behavior
- Modules not responding to scan tool
Common causes
- Damaged CAN bus wiring or connectors
- Faulty control module on the bus
- Corroded or loose ground connections
- Failed CAN transceiver
Diagnostic steps
- Scan all modules for stored U-codes
- Inspect CAN wiring and connectors for damage
- Measure CAN bus resistance and voltage
- Isolate faulty module by disconnecting nodes
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Other Network codes on this vehicle
U0001
High Speed CAN Communication Bus
U0002
High Speed CAN Communication Bus Performance
U0003
High Speed CAN Communication Bus (+) Open
U0004
High Speed CAN Communication Bus (+) Low
U0005
High Speed CAN Communication Bus (+) High
U0006
High Speed CAN Communication Bus (-) Open
U0007
High Speed CAN Communication Bus (-) Low
U0008
High Speed CAN Communication Bus (-) High
U0009
High Speed CAN Communication Bus Shorted Together
U0010
Medium Speed CAN Communication Bus