Skip to content
Book on WhatsApp

P25A4

Fuel Mode Select Switch Circuit

General electrical fault on the fuel mode select switch — used on bi-fuel vehicles (CNG/LPG/H2/gasoline) so the driver can pick the active fuel. With the input invalid, the ECM falls back to the default fuel and disables operator-selectable switching.

  • Check engine light: Yes
  • Emissions related: No
  • Repair difficulty: medium

Common causes

Ordered by how often each turns out to be the cause.

  • Open or shorted switch wireCommon

Parts involved

  • Fuel Mode Switch

P25A4 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.