CAN messages sent at irregular intervals on busy networks

Published: 8 October 2024 · Status: Resolved in firmware 2.0.1 · Last reviewed: 2026-08-07

Affected

Any device running firmware older than 2.0.1, on a network carrying enough traffic for the timing to matter. It showed up first on installations connected to Haltech engine management, and it can affect OEM networks the same way.

A quiet two-node bench bus will not show it. The symptom scales with how loaded the bus is, which is why it tends to appear when a configuration moves from the bench into the car.

What happens

Messages arrive late, or stop arriving. What the receiving device does with that varies, and the two reported cases look nothing alike:

  • BMW E9x — switching between automatic and manual transmission modes in the DME stops working, or responds late.
  • Haltech — torque management is not performed at all, or the wrong torque management action is taken.

Both read as a fault in the receiving ECU rather than in the transmitter, which is what makes this one expensive to chase.

Why

The device's internal CAN module was misconfigured. Rather than transmitting at the intervals the configuration asked for, it sent at irregular ones — which on a busy network means contributing more traffic than the bus budget allowed for, and pushing the network toward the point where messages are delayed or lost outright.

The misconfiguration was internal to the CAN module. Nothing in a user configuration caused it and nothing in one could avoid it.

What to do

Update to firmware 2.0.1 or later. There is no configuration workaround — the fix is in the firmware.

If you are still seeing delayed or missing messages after updating, the cause is something else, and the bus itself is the place to start: CAN bus diagnostics covers termination, bitrate and error counters.

Status

Resolved in firmware 2.0.1, which lists "Improved CAN bus traffic handling" under Communication in its release notes.

A release candidate was offered directly to owners at the time of the notice. That is no longer the route — the fix is in the released firmware.