High Speed CAN Communication Bus (+) Low
2004-2016 Aston Martin DB9 6.0L V12
Description
The CAN High wire voltage is lower than expected, indicating a short to ground or excessive load on the bus.
Symptoms
- Communication failures
- Multiple DTCs from various modules
- Intermittent system operation
Common Causes
- CAN H wire shorted to ground
- Module pulling CAN H low
- Damaged wiring insulation
- Water intrusion in connector
Diagnostic Steps
- Measure CAN H voltage
- Disconnect modules one at a time to find short source
- Inspect wiring for chafing against ground
- Check connectors for moisture
Repair Notes
Find and repair the short to ground on the CAN H wire. Inspect for damaged insulation.
Related Codes
Other Network Codes
- U0001High Speed CAN Communication Bus
- U0002High Speed CAN Communication Bus Performance
- U0003High Speed CAN Communication Bus (+) Open
- 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
U0004 on Other Vehicles
Aston Martin DB11
2016-2024 4.0L V8 Twin Turbo
Aston Martin DB11
2016-2024 5.2L V12 Twin Turbo
Aston Martin DB7
1994-2003 3.2L I6 Supercharged
Aston Martin DBS Superleggera
2019-2024 5.2L V12 Twin Turbo
Aston Martin DBX
2020-2024 4.0L V8 Twin Turbo
Aston Martin Vantage
2005-2024 4.7L V8
Aston Martin Vantage
2018-2024 4.0L V8 Twin Turbo
Common Questions
What does code U0004 mean on a 2004-2016 Aston Martin DB9?
U0004 stands for "High Speed CAN Communication Bus (+) Low". The CAN High wire voltage is lower than expected, indicating a short to ground or excessive load on the bus.
What are the symptoms of U0004 on a Aston Martin DB9?
Common symptoms of U0004 include: Communication failures, Multiple DTCs from various modules, Intermittent system operation.
What causes U0004 on a 2004-2016 Aston Martin DB9?
Common causes of U0004 include: CAN H wire shorted to ground, Module pulling CAN H low, Damaged wiring insulation, Water intrusion in connector.