Powertrain, generic (extended)

P2668 Fuel Mode Indicator Lamp Control Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Bi-fuel vehicles tell the driver which fuel is in use through a small indicator, often built into the fuel selector button. On GM's 2016 Silverado and Sierra with CNG the light is off on gasoline, steady on natural gas, flashes once per second during a changeover and flashes about ten times per second when the CNG system has a fault; the 2015 Impala Bi-Fuel uses a similar light in its CNG switch. P2668 indicates that the module driving this lamp has found a fault in its control circuit, such as an open wire or a failed bulb or LED. No manufacturer documents the code publicly. Fuel switching itself is unaffected, but the driver loses the fuel mode display and the error warning. P26E2 and P26E3 are the low and high variants.

Likely causes

Indicator LED or bulb in the selector switch failed
Open wire or loose connector at the switch
Lamp driver in the control module defective

Symptoms

  • Fuel mode lamp stays dark in gas mode
  • No flashing during fuel changeover or on errors

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

P26E2P26E3P25A4P2665

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