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U0019 — Low Speed Can Communication Bus

Generic OBD-II · all makesNetwork / communication

U0019 indicates a problem with the vehicle's low-speed CAN communication network, meaning the bus is not transmitting data at the expected speed. It is a network-level fault rather than a direct engine issue.

Symptoms

What causes it — most likely first

1. Faulty low-speed CAN bus wiring or connector

Damaged, corroded, or loose wires/connector pins on the low-speed CAN network can interrupt signal integrity and trigger the code.

2. Corroded or loose bus connections

Oxidation or poor contact at termination resistors or splice points often causes intermittent bus failures.

3. Faulty low-speed CAN module (e.g., body control module)

A defective module that transmits or receives data on the low-speed bus can cause the network to drop out.

4. Faulty Powertrain Control Module (PCM)

Although rare, a PCM that malfunctions on the CAN bus can generate a U0019, typically after other causes have been ruled out.

5. Faulty other control module on the bus

Modules such as the ABS or instrument cluster that develop internal faults may disrupt the low-speed CAN communication.

How it's diagnosed

  1. Connect a scan tool and confirm U0019 is present with supporting data.
  2. Visually inspect the low-speed CAN wiring harness and connectors for damage, corrosion, or loose pins.
  3. Measure bus voltage and resistance to verify proper termination and continuity.
  4. Check power and ground circuits for each module on the low-speed network.
  5. Use a scan tool to monitor communication status of all modules and isolate the non-responsive one.
  6. Replace the identified faulty module only after confirming the bus is otherwise healthy.

Code facts & related codes

SystemNetwork / communication
StandardizationSAE generic — identical on every make
Related codesU0010 — Medium Speed Can Communication BusU0011 — Medium Speed Can Communication Bus PerU0012 — Medium Speed Can Communication Bus OpeU0013 — Medium Speed Can Communication Bus LowU0014 — Medium Speed Can Communication Bus HigU0015 — Medium Speed Can Communication Bus O

Frequently asked

Can I fix U0019 by simply replacing the PCM?

No. Replacing the PCM is rarely the solution; most often the issue is wiring, a connector, or a non-PCM module on the low-speed CAN bus.

Is a loose battery terminal a common cause of U0019?

A weak battery can affect overall electrical stability, but a loose terminal is not a typical direct cause of a low-speed CAN bus fault.

Do I need to replace the entire wiring harness?

Usually not. Most problems are resolved by repairing or cleaning the specific wires or connectors that are damaged or corroded.

Can I clear the code and ignore it?

Clearing the code without fixing the underlying bus issue will likely cause it to reappear, and drivability problems may persist.