* Fuel System Compatibility: Pontiac Transports, especially older models, were not designed to handle the higher ethanol content of blends like E85. Ethanol is corrosive and can damage or degrade certain rubber and plastic components in the fuel system, including fuel lines, seals, and gaskets. These components may not be compatible with the increased ethanol content, leading to leaks or malfunctions.
* Sensor Readings: The ethanol's different combustion properties affect sensor readings. The oxygen sensors (O2 sensors), which monitor the air-fuel mixture, will detect a deviation from the expected readings for gasoline designed for the car. This discrepancy triggers the check engine light as a way of alerting the driver to a potential problem.
* Engine Calibration: The engine's computer (ECU) is calibrated for a specific fuel type (typically gasoline with a low ethanol content). The different combustion characteristics of ethanol will cause the ECU to detect issues and thus illuminate the check engine light. The engine may run poorly or inefficiently as well.
In short, the check engine light is a safety measure indicating that the fuel system is likely being compromised and/or the engine isn't running optimally because of the incompatibility between the ethanol blend and the vehicle's design. Using E85 in a car not designed for it can lead to significant and costly repairs. Always refer to your owner's manual to determine the appropriate fuel type for your vehicle.
