01 The Little-Known Reason Mechanics Don’t Always Reset Your E… • 02 B0042, B0043, and B0044: Left Front or Driver Frontal Deplo… • 03 Electric Vehicles: The Future of Transportation Is Here, an… • 04 Engine CC: What It Is and How to Calculate It • 05 Does Auto Start - Stop Wear Out a Starter? • 06 How to Fix a Car That Loses Power in 2nd Gear: A Comprehens… • 07 Drivers Urged To Check Their Car Mirrors After Hidden Safet… • 08 Engineers Reveal Why Most Car Doors Are Designed To Rip Apa… • 09 Avoid These Brake Pads If You Drive in Rainy or Coastal Reg… • 10 Mechanics Shocked At How Many Cars Are Destroyed By Owners … •

DTC codes / U01xx · Lost communication with a control module / U019A

U019ALost Communication With Tachograph Module

U019A is a generic network communication code indicating that one or more control modules on the vehicle's Controller Area Network (CAN) bus have stopped receiving messages from the tachograph module. The tachograph module is a dedicated electronic unit that records vehicle speed, distance, driver activity, and engine data for commercial compliance, and when it goes silent the monitoring modules set this code after a defined timeout period.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaLost communication with a control module

Symptoms you may notice

  • The malfunction indicator lamp (MIL) or a dedicated communication warning light illuminates on the dashboard.
  • Often no symptoms besides the warning light, because the tachograph is a logging device and does not affect engine operation.
  • The tachograph display may be blank, frozen, or showing a communication error message.
  • Fleet compliance data may stop recording, leading to missing or incomplete driver records.
  • Other unrelated modules may log communication codes if the tachograph module is dragging down the CAN bus.
  • In some vehicles, the instrument cluster may show a tachograph or network fault message.

Common causes, most likely first

  1. A blown fuse or poor power/ground connection at the tachograph module, which is the most common cause of a silent module.
  2. Damaged or corroded wiring in the CAN bus branch to the tachograph, including chafed harnesses or water intrusion at connectors.
  3. A failed tachograph module itself, often due to internal electronics failure or a dead internal backup battery.
  4. Loose or unseated connector pins at the tachograph module or at an intermediate CAN junction point.
  5. A shorted or open CAN bus segment that isolates the tachograph from the rest of the network.
  6. Incorrect configuration or coding after a module replacement, causing the tachograph not to broadcast on the bus.
  7. A faulty gateway module that fails to route tachograph messages to the modules that monitor them.

How to diagnose and fix it

  1. Verify the code with a full-system scan and record all communication codes across every module to see which modules are affected.
  2. Check the tachograph fuse and measure battery voltage and ground continuity at the tachograph connector before condemning any part.
  3. Inspect the CAN wiring and connectors between the tachograph and the nearest network junction for damage, corrosion, or loose pins.
  4. Measure CAN bus resistance and voltage at the tachograph connector to confirm the bus is healthy and the module is receiving power.
  5. If power, ground, and bus signals are good, substitute a known-good tachograph module or perform a module communication test with a scan tool.
  6. After any repair, clear codes and verify that the tachograph module appears on the network and that no communication codes return after a road test.
  7. If the tachograph is replaced, complete any required configuration or coding so the new module broadcasts correctly on the CAN bus.

Why a silent tachograph is rarely the module's fault

  • A tachograph that has lost power or ground will set U019A even though the module itself is perfectly functional, so always check fuses and connectors before replacing hardware.
  • Because the tachograph is a compliance recorder, many drivers notice no drivability change at all and assume the code is harmless, but ignored communication faults can mask a failing network.
  • Water intrusion at the tachograph connector or a chafed harness behind the dashboard is a frequent hidden cause that a simple module swap will not fix.
  • U019A can be set by a gateway or central module that fails to route tachograph messages, so the fault may live far from the tachograph itself.
  • After a tachograph replacement, missing configuration can cause the new module to remain silent on the bus and set the same code again.

Can I keep driving with U019A?

The vehicle will usually drive normally because the tachograph is a logging device, but you should avoid long trips until the fault is repaired because compliance data may not be recorded. If the warning light is accompanied by other network codes or instrument cluster faults, have the vehicle inspected promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage