What Does U0030 Mean?
The CAN-H (positive) line of communication Bus A has an open circuit, meaning there is a complete break in the wire preventing signal transmission. This results in complete or partial loss of network communication on this bus.
Safety Warning
Critical safety systems including ABS, airbags, and stability control may be completely disabled. Vehicle should not be driven until repaired.
Common Causes
40%
Broken or severed CAN-H wire in harness, often at flex points or pinch areas
25%
Disconnected or backed-out connector terminal for CAN-H circuit
20%
Damaged connector causing terminal to lose contact with pin
10%
Open circuit within a control module's CAN transceiver
5%
Rodent damage or physical damage to wiring harness
Diagnostic Steps
1
Step 1: Locate CAN Bus A wiring diagram and identify CAN-H wire color and routing path
2
Step 2: Measure voltage on CAN-H line at multiple points; an open will show no voltage downstream of break
3
Step 3: Perform continuity test on CAN-H wire from module to module to locate open circuit
4
Step 4: Inspect connectors along CAN-H circuit for backed-out pins, broken terminals, or damaged connector bodies
5
Step 5: Visually inspect harness routing for physical damage, particularly at frame rails, doors, and under-vehicle areas
Estimated Repair Cost
$200 - $1,200
Parts + labor, varies by vehicle and location
The CAN-H (positive) line of communication Bus A has an open circuit, meaning there is a complete break in the wire preventing signal transmission. This results in complete or partial loss of network communication on this bus.
The most common cause of U0030 (Vehicle Communication Bus A (+) Open) is: Broken or severed CAN-H wire in harness, often at flex points or pinch areas
Typical repair costs for U0030 range from $200 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Critical safety systems including ABS, airbags, and stability control may be completely disabled. Vehicle should not be driven until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0030 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
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