What Does U0027 Mean?
The CAN bus negative (-) and positive (+) lines are shorted together, eliminating the differential voltage required for proper communication. This creates a single-wire circuit instead of the required twisted pair.
Common Causes
40%
Pinched or crushed harness causing CAN+ and CAN- wires to short together
25%
Failed module with internal short between CAN+ and CAN- circuits
20%
Damaged connector with cross-contamination or melted terminals
10%
Water intrusion causing short between CAN circuits
5%
Improper repair with CAN+ and CAN- wires crossed or spliced together
Diagnostic Steps
1
Step 1: Measure resistance between CAN+ and CAN- at diagnostic port; low or zero resistance confirms short
2
Step 2: Disconnect modules one at a time and recheck resistance to isolate internal module short vs. wiring short
3
Step 3: Inspect all accessible connectors for melted, crossed, or damaged terminals on CAN circuits
4
Step 4: Examine harness routing for pinch points, particularly at body seams, door hinges, and cable tie locations
5
Step 5: If short persists with modules disconnected, segment test harness sections using wiring diagram to locate fault
Estimated Repair Cost
$200 - $1,000
Parts + labor, varies by vehicle and location
The CAN bus negative (-) and positive (+) lines are shorted together, eliminating the differential voltage required for proper communication. This creates a single-wire circuit instead of the required twisted pair.
The most common cause of U0027 (Low Speed CAN Communication Bus (-) shorted to Bus (+)) is: Pinched or crushed harness causing CAN+ and CAN- wires to short together
Typical repair costs for U0027 range from $200 to $1,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Complete network failure will occur, affecting multiple vehicle systems. Critical safety features may be disabled, and vehicle may not start or operate properly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0027 to identify the root cause.
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Quick Info
Category
Network
System
Network Communications
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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