P264F — Engine Serial Number Not Programmed or Incompatible

P264F is stored when the ECU sees not configured on the circuit named in the code. That describes how the circuit is behaving, not which part has failed — the wiring, the connector and the component itself can all produce it, which is why the checks below start with the cheapest.

Common causes

The cause is almost always one of a few things. Here they are — P264F rarely comes from anything outside this list:

• Replacement module fitted but never coded to the car
• Configuration lost after a battery or software event
• Wrong part number for this vehicle specification
• Adaptation or learning procedure not carried out after a repair

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. This is a coding fault, not a broken part — do not replace anything yet
2. Confirm the fitted module part number matches the vehicle specification
3. Run the coding or adaptation procedure with equipment that supports this brand
4. Re-check for the code after the adaptation completes

That is what holds for P264F in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.