Alex is absolutely correct, if I could add something from a clue that you gave us about the fuel cap light. On a rare occasion I have had the fuel tank pressure sensor short to vref which will cause the power-train control module to shut down. The vref circuit is a 5 volt circuit that several sensors use as a reference to for proper sensor voltage feedback. The fuel tank pressure sensor tells the power-train control module how much pressure is in the fuel tank, when the PCM tells the purge valve to open and pull a vacuum on the tank, the voltage will go from 2.65 to 1.50 approximately. And when the sensor fails, it usually fails high at 5 volts so now the PCM thinks that the fuel cap is off because the voltage is not coming down when a vacuum is commanded. Throttle position sensor, dpfe/egr sensor, fuel tank pressure sensor, are some of the most common vref short failures that I have seen. This is only one scenario, but if the vehicle will not start, probe the brown with white wire for 5 volts with the key on at any of those sensor connectors, or just unhook them in a no start condition to see if it starts. And if you have a scan tool that can look at the sensor readings, the ftp should read 2.65v with the key on engine off.
Wednesday, September 11th, 2019 AT 7:49 AM