Powertrain, generic (extended)

P26E3 Fuel Mode Indicator Lamp Control Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P26E3 is the opposite case of P26E2: the module that drives the fuel mode lamp sees a voltage on its control line that is higher than its commanded state allows. With a ground-side driver this is usually a short to a 12 V feed, or an open lamp that lets the line float to supply level; with a positive-side driver it points to outside voltage reaching the output. Many output stages switch off to protect themselves once they detect such a fault. The lamp matters on bi-fuel vehicles because it is the driver's only cue to the active fuel: on GM's 2016 Silverado and Sierra CNG it flashes once a second during a changeover and around ten times a second if the gas system has failed. No manufacturer documents P26E3 publicly, and a lamp circuit fault does not alter the exhaust emissions.

Likely causes

Lamp control wire shorted to a battery or ignition feed
Burnt-out bulb or open LED in the selector switch
Damaged or wet connector at the selector switch

Symptoms

  • Fuel mode lamp stays dark
  • Driver cannot tell which fuel is in use

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–250
Time0.3–1.5 h

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

Parts involved

fuel mode lampinstrument clusterwiring harness

Related codes

P26E2P2668P25A4

References: gmc.com, static.nhtsa.gov.