What Does U1900 Mean?
The Controller Area Network (CAN) communication bus has detected a fault preventing proper data exchange between modules. This is a critical network issue that can affect multiple vehicle systems depending on which CAN bus is affected (high-speed, medium-speed, or low-speed).
Safety Warning
Can cause critical safety systems like ABS, airbags, and stability control to malfunction. Vehicle may not start or may experience severe drivability issues. Do not drive until repaired.
Common Causes
30%
Short to ground or short to power in CAN bus wiring harness
25%
Failed control module pulling down or disrupting the CAN bus
20%
Damaged or corroded CAN bus termination resistors
15%
Water intrusion or corrosion in module connectors causing intermittent communication
10%
Aftermarket device improperly connected to OBD-II port disrupting CAN bus
Diagnostic Steps
1
Step 1: Measure CAN High and CAN Low voltage at the data link connector with key on engine off (should read approximately 2.5V each, 0V difference)
2
Step 2: With key on, check for proper voltage difference between CAN High (3.5V) and CAN Low (1.5V) during communication
3
Step 3: Measure total CAN bus resistance with key off and all modules connected (should read 60 ohms indicating two 120-ohm termination resistors in parallel)
4
Step 4: Disconnect modules one at a time while monitoring CAN bus voltage to identify which module is disrupting communication
5
Step 5: Inspect CAN bus wiring for damage, pinching, or water intrusion, especially in areas prone to flexing or corrosion
Estimated Repair Cost
$200 - $1,500
Parts + labor, varies by vehicle and location
The Controller Area Network (CAN) communication bus has detected a fault preventing proper data exchange between modules. This is a critical network issue that can affect multiple vehicle systems depending on which CAN bus is affected (high-speed, medium-speed, or low-speed).
The most common cause of U1900 (CAN Communication Bus Fault) is: Short to ground or short to power in CAN bus wiring harness
Typical repair costs for U1900 range from $200 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Can cause critical safety systems like ABS, airbags, and stability control to malfunction. Vehicle may not start or may experience severe drivability issues. Do not drive until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U1900 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Network
System
Vehicle Communication Network
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
