U0003
High Speed CAN Communication Bus (+) Open
1992-1998 BMW 325i E36 2.5L I6 M50 🇷🇺
High SeverityNetwork
Description
The CAN High wire is open, disrupting high-speed bus communication. CAN H carries the dominant high signal.
Symptoms
- Multiple modules offline
- Warning lights illuminated
- Systems inoperative
- No scan tool communication on some modules
Common Causes
- Broken CAN H wire
- Corroded CAN H terminal
- Damaged CAN bus connector
- Wiring harness damage
Diagnostic Steps
- Measure voltage on CAN H (should be ~2.5V idle, ~3.5V dominant)
- Check continuity of CAN H wire
- Inspect CAN bus connectors
- Locate break using voltage drop test
Repair Notes
Locate and repair the open in the CAN H wire. Check all splice points.
Related Codes
Other Network Codes
- U0001High Speed CAN Communication Bus
- U0002High Speed CAN Communication Bus Performance
- U0004High Speed CAN Communication Bus (+) Low
- U0005High Speed CAN Communication Bus (+) High
- U0006High Speed CAN Communication Bus (-) Open
- U0007High Speed CAN Communication Bus (-) Low
- U0008High Speed CAN Communication Bus (-) High
- U0009High Speed CAN Communication Bus Shorted Together
- U0010Medium Speed CAN Communication Bus
- U0028Vehicle Communication Bus A Performance
U0003 on Other Vehicles
Common Questions
What does code U0003 mean on a 1992-1998 BMW 325i E36?
U0003 stands for "High Speed CAN Communication Bus (+) Open". The CAN High wire is open, disrupting high-speed bus communication. CAN H carries the dominant high signal.
What are the symptoms of U0003 on a BMW 325i E36?
Common symptoms of U0003 include: Multiple modules offline, Warning lights illuminated, Systems inoperative, No scan tool communication on some modules.
What causes U0003 on a 1992-1998 BMW 325i E36?
Common causes of U0003 include: Broken CAN H wire, Corroded CAN H terminal, Damaged CAN bus connector, Wiring harness damage.