2015 Chevy Express Check Engine Light with P0171, P0174, and P0113 Codes After E85 Usage
A 2015 Chevrolet Express owner reports the check engine light is on due to persistent trouble codes P0171 (System Too Lean Bank 1), P0174 (System Too Lean Bank 2), and P0113 (Engine Coolant Temperature Sensor 'A' Circuit Low). The vehicle was previously used with E85 fuel, which may contribute to the lean condition. Despite replacing components including the fuel pump injectors, MAF sensor, oxygen sensors, and PCM, the issue remains unresolved. The user is seeking guidance on potential root causes and troubleshooting steps for this persistent problem.
Why was E85 fuel used in this vehicle? Using E85 can cause lean misfires and affect sensor readings, especially in vehicles not designed for it. Consider the possibility of vacuum leaks or incorrect fuel pressure. Even with a new fuel pump, verify fuel system pressure. Use an OBD2 scanner to monitor live data—check MAF, MAP, fuel trims, and oxygen sensor voltages—to identify where the lean condition is occurring.