What Does U0045 Mean?
The negative and positive wires of communication bus B are shorted together, causing complete network failure. This eliminates the differential signaling required for proper bus communication.
Common Causes
45%
Damaged harness causing CAN B(+) and B(-) wires to contact each other
30%
Faulty control module with internal short between bus lines
15%
Connector corrosion or contamination bridging bus terminals
7%
Improper repair or splice creating short between bus wires
3%
Rodent damage to wiring harness
Diagnostic Steps
1
Step 1: Measure resistance between CAN B(+) and CAN B(-) lines; should show approximately 60 ohms, not near zero
2
Step 2: Disconnect all modules from bus B and recheck resistance between bus lines
3
Step 3: If short clears with modules disconnected, reconnect modules one at a time to identify faulty module
4
Step 4: If short remains with modules disconnected, inspect harness for physical damage, especially at flex points
5
Step 5: Replace damaged harness section or faulty module causing the short circuit
Estimated Repair Cost
$200 - $1,800
Parts + labor, varies by vehicle and location
The negative and positive wires of communication bus B are shorted together, causing complete network failure. This eliminates the differential signaling required for proper bus communication.
The most common cause of U0045 (Vehicle Communication Bus B (-) shorted to Bus B (+)) is: Damaged harness causing CAN B(+) and B(-) wires to contact each other
Typical repair costs for U0045 range from $200 to $1,800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Complete loss of bus B communication can disable critical systems including engine management, transmission, ABS, and airbag systems. Vehicle may not operate safely or at all.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0045 to identify the root cause.
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Quick Info
Category
Network
System
Vehicle Communication Network
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
