Battery voltage at a module connector does not prove that every internal supply is present. The input protection path sits between the vehicle supply and the electronics it protects.

How to narrow it down

A board-level assessment should establish where the supply stops and whether a downstream fault is influencing the protection circuit. Include any reversed connection or jump-start history. External power and grounds still need proper testing before internal repair is considered.

What to include with the fault report

Send the module label, incident history and confirmed connector supply measurements.

A protection device must not be bridged to return a module to service. Its purpose and the cause of failure need to be addressed.

Speak to AXION

For ECU testing and component-level repair, send your vehicle details and fault report. Workshop assessment is in Didcot, Oxfordshire. Suitable postal or remote work is confirmed before booking.

Technical background from Nexperia. The referenced design explains the principle; the vehicle-specific procedure determines the repair.

Related reading — A shorted transient suppressor and a module supply fault. Browse all vehicle-electronics diagnostic notes or return to the repair library.