High Speed CAN Communication Bus (+) Low
2007-2012 Nissan Altima 2.5L I4
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
Nissan 200SX
1995-1998 1.6L I4 GA16DE
Nissan 200SX SE-R
1995-1998 2.0L I4 SR20DE
Nissan 240SX
1995-1998 2.4L I4 KA24DE
Nissan 300ZX
1990-1996 3.0L V6 VG30DE
Nissan 300ZX Twin Turbo
1990-1996 3.0L Twin-Turbo V6 VG30DETT
Nissan 350Z
2003-2006 3.5L V6 VQ35DE
Nissan 350Z
2007-2009 3.5L V6 VQ35HR
Nissan 370Z
2009-2020 3.7L V6 VQ37VHR
Common Questions
What does code U0004 mean on a 2007-2012 Nissan Altima?
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 Nissan Altima?
Common symptoms of U0004 include: Communication failures, Multiple DTCs from various modules, Intermittent system operation.
What causes U0004 on a 2007-2012 Nissan Altima?
Common causes of U0004 include: CAN H wire shorted to ground, Module pulling CAN H low, Damaged wiring insulation, Water intrusion in connector.