What Does U0074 Mean?
Communication bus B has lost power or is completely non-functional. This secondary network is not transmitting any data between modules.
Common Causes
30%
Blown fuse supplying power to bus B network modules
25%
Open or broken wire in bus B communication lines
20%
Failed module acting as bus B master preventing network operation
15%
Corroded connector or poor ground connection on bus B circuit
10%
Damaged termination resistor causing bus B signal collapse
Diagnostic Steps
1
Step 1: Check all fuses associated with bus B network and connected modules
2
Step 2: Verify proper power supply voltage to bus B circuit at main junction points
3
Step 3: Test continuity of bus B positive and negative wires from end to end
4
Step 4: Check bus B termination resistors at each end of network using ohmmeter (should read 60 ohms between bus+ and bus-)
5
Step 5: Disconnect modules one at a time to identify if a failed module is pulling down the bus
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
Communication bus B has lost power or is completely non-functional. This secondary network is not transmitting any data between modules.
The most common cause of U0074 (Control Module Communication Bus B Off) is: Blown fuse supplying power to bus B network modules
Typical repair costs for U0074 range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May disable convenience features and some safety systems. Vehicle typically remains drivable but with reduced functionality.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0074 to identify the root cause.
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Quick Info
Category
Network
System
Network Communication
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
