KESS or K-Tag generic error

A generic error is the tool telling you that a step did not complete and that it does not have
a more specific message for why. It is not a diagnosis. The same message covers a long list of
causes, which is why working through them in order beats guessing.

In practice it almost always means the exchange between the tool and the ECU was interrupted
or the tool did not get the reply it expected. It rarely means the ECU is damaged.

Work through these in order

1. Voltage. Put a proper battery support unit on the vehicle, not a trickle
   charger, and check what the voltage is actually doing rather than assuming. This is the first
   check because it is the most common cause and the easiest to rule out.
2. The physical connection. OBD plug fully seated and not loose in the socket.
   The correct cable or adapter for the job. On a bench or boot connection, check every wire against
   the diagram again before you retry, including the ground.
3. The right protocol for the right ECU. Identify the ECU from the hardware and
   software numbers, not from what the car is supposed to have. Facelifts, mid year changes and
   previously replaced ECUs all catch people out here.
4. Anything else on the bus. Unplug other diagnostic tools, and disconnect
   hardwired trackers, dashcams and aftermarket alarms. Any of them can talk over the top of the
   tool.
5. USB and laptop. Straight into the laptop, no hub. Try a different port and a
   different cable. Turn off sleep, hibernate and USB selective suspend. Antivirus and backup
   software can both interrupt a session.
6. Tool software and firmware. Both up to date, and both actually finished
   updating rather than part way through.
7. Retry once with everything above corrected. If it fails the same way twice
   with a clean setup, stop retrying and send it to us.

Do not keep retrying a write

Retrying a failed read costs you time. Retrying a failed write costs you an ECU. If the error
appeared during a read or an identification, retrying is reasonable. If it appeared during a
write, treat it as a writing error, leave everything connected, and follow the recovery steps for
that instead.

Why we ask for the log

Because the message on screen is the same for a flat support unit, a loose plug and an
unsupported ECU variant, and the log is what separates them. It records the protocol used, what
the ECU replied, and the point at which it stopped. Attach it to your ticket on the dealer portal
along with any read files.

The exact wording of the error and where the tool keeps its logs both change between versions,
so what you see may not match word for word. The order of the checks above does not change.