U0044 is a network communication code indicating that the controller area network (CAN) bus labeled 'B' has a signal that is stuck or biased abnormally high. It means one of the data lines on Bus B is seeing a voltage level that should not be present, disrupting communication between the modules that share that bus.
Chafed insulation, pinched looms, or a conductor pinched between the body and a bracket can short the bus wire to 12 V or to a switched feed, driving the line high.
Backed-out terminals, water ingress, or green corrosion at a module plug can bias the bus high or open the circuit enough to produce a stuck-high condition.
Alarm systems, remote starters, audio interfaces, or telematics modules spliced into CAN-B can load or short the line, especially when their own wiring fails.
Each CAN bus normally has two 120-ohm termination resistors. If one is lost (corroded joint, broken splice, removed module), bus voltage levels shift and a high-bias code can be set.
An internal transistor failure in any module on the bus can clamp the line at battery voltage. Identifying which one requires isolating modules one at a time.
A shorted transceiver inside the PCM can hold Bus B high. This is uncommon and should only be considered after every wiring, connector, and peripheral-module cause has been ruled out.
No. In real-world cases, the PCM is the cause of U0044 only on rare occasions. The code almost always points to wiring damage, a connector issue, a failed termination, an aftermarket tap, or another module on the bus. Replacing the PCM without checking those items first is one of the most common and most expensive misdiagnoses for this code.
Yes. Voltage spikes, a failing battery, or improper jump-starting can corrupt bus communication and set transient U-codes including U0044. If the code does not return after clearing and the charging system checks out, it may have been event-related rather than a persistent fault.
It depends on which modules are affected. If critical systems such as the transmission, ABS, or engine controller are losing communication, the vehicle may enter a limp mode or stall, and it should not be driven. If only a non-critical body module is offline, limited driving is usually possible until repair.