U019A: Lost Communication With Tachograph Module

What it means

ECU lost communication with the tachograph module (commercial vehicle driving-time recorder, EU regulation).

At a glance

• Usually lights the warning light of the system that lost communication

How it works

The tachograph records commercial-vehicle driving and rest information, and communicates status over the vehicle network. The control module sets U019A when it stops receiving expected messages from the tachograph module; the fault concerns communication, not necessarily the recorder itself.

Common causes

Most likely first.

1. Module unpowered
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Tachograph functions may be unavailable
• Other communication codes

How to diagnose it

1. Use a scan tool to save freeze-frame data and check whether U019A is current, then scan other modules for related communication codes.
2. Check whether the tachograph powers up and displays warnings or faults, since a dead unit may have lost its supply.
3. Inspect the tachograph module's power, ground, connectors, and network wiring for a blown fuse, corrosion, looseness, or damage.
4. Check whether a gateway has related routing faults and confirm it is configured for the vehicle's network.
5. Have the CAN network and its terminating resistance checked against the manufacturer's specification, especially if several modules report communication faults.

Common fixes

• Repair a loose, corroded, or damaged tachograph connector or wiring.
• Restore the tachograph module's power or ground supply, or replace a failed fuse after checking for the cause.
• Correct a gateway configuration or routing fault using the vehicle's specified procedure.
• Repair the CAN network or replace an out-of-spec terminating resistor.

Can I keep driving?

If the tachograph is unavailable, required driving-time recording may be affected; follow applicable operating requirements and avoid relying on the recorder until it works. If other communication faults or vehicle warnings appear, arrange diagnosis before continuing commercial use.