Powertrain, generic (extended)

P25A7 Fuel Mode Select Switch Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P25A7 reports a fuel mode select switch signal above the accepted window. With a pull-up input this mostly means the switch never closes its path – an open signal or return wire, a connector half off, a broken switch – or that the line has contact with a supply voltage, for example where an alternative-fuel conversion tapped into nearby wiring. No manufacturer documents P25A7 publicly; it follows CARB's demand that every computer input be checked for out-of-range readings. GM's 2016 Sierra and Silverado bi-fuel supplement shows the switch also carries the fuel indicator light, so a supply fault can affect both. Opposite to P25A6, measuring for voltage on the signal line with the switch unplugged separates a short to power from an open. Selection by switch stops working.

Likely causes

Open signal or return wire, connector not seated
Signal wire touching a supply voltage, e.g. after aftermarket wiring
Switch contact broken open

Symptoms

  • Switch has no effect
  • Fuel indicator on the switch may stay dark

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–300
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel mode switch

Related codes

P25A4P25A5P25A6P25A8

References: law.cornell.edu, gmc.com.