P26E2: Fuel Mode Indicator Lamp Control Circuit Low

Bi-fuel vehicles show the active fuel with an indicator, often a lamp in the selector switch. GM's 2015 Impala bi-fuel lights it while running on CNG and flashes it during a fuel change; GM's 2016 CNG pickups also flash it fast to signal a gas system fault, and Ford's earlier bi-fuel trucks combined the ALT/GAS selector with its lamp in one assembly. P26E2 means the controlling module reads the lamp control circuit as too low. Where the module switches the lamp on the positive side, that typically points to a short to ground in the wire or the lamp; with a ground-side driver the same reading can mean an open path. No manufacturer documents P26E2 publicly. The fuel change itself still works, but the driver may see a lamp that is dark or always lit and loses the fault warning. P2668 is the general circuit fault.

Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

Symptoms

Fuel mode lamp dark or permanently lit
No visible warning when the gas system has a fault

Most likely causes

Lamp control wire chafed to ground
Shorted LED or bulb in the fuel selector switch
Faulty lamp output in the controlling module

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and wiring
With the connector unplugged, check whether the signal wire is making contact with ground.
Use live data to compare the reading with actual conditions
Measure power, ground, and signal
Replace the sensor if the circuit is good

Good to know

Repair difficulty: easy

What each character of P26E2 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
6: Control modules and outputs
E2: Specific fault in that system

Frequently asked questions

Can I keep driving with code P26E2?

You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

What causes code P26E2?

The most common causes are: lamp control wire chafed to ground; shorted LED or bulb in the fuel selector switch; faulty lamp output in the controlling module.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.