Engine check engine light came on. Also error message BPEMI

The loose gas cap can mess with your vacuum system but a check engine light means check your computers error messages. Have a mechanic do so before we speculate too far.

Check the resistance of the injectors. They should measure 14 ohms cold. Another check is to run the engine, and with a long screwdriver placed against each injector in turn, put your ear against the screwdriver handle to check if all injectors sound the same. Any one that is different is probably malfunctioning.

That makes no sense...sorry

there is a DTC error stored, in the ECU. (scan tools show this)
there is a car puter, error, message that really means
the gas tank is not holding air pressure.."EVAP sys"
and 99% of the time, that is "a loose gas cap"
it can take many driving cycle to clear this code.
or 1second with any scan tool, even a $30 tool.

What error message are you receiving? If you are talking about your check engine light (CEL) then you will need to clear the codes for it to go away, or it must be driven through a series of specific events for the computer to clear itself, just take it down to your local auto store and have them scan and clear codes. At 14.5v you should not get the battery light, you may want to check your wiring to your ECM. With your old alternator running at 16v I would say it is possible something was damaged. I know many manufacturers do not protect the computer from spikes from alternators, I have seen this twice in the field, and actually had personal experience as well. This will require much more knowledge about your vehicle and electricity to understand what pins to test and what you should be looking for.

Thwe check engine light is on because the computer has detected a problem. Take the car to Autozone and they will scan it for free and tell you what the problem is. If you have a question, let me know. I am here to help you.

the engine light can mean many different error messages. The only way to find out is to hook it to a computer reading module. Try visiting a dealer or your local garage and see if they will hook it up for you, it only takes a moment. Then it will give the error message code 9 times out of ten its the oxygen censor.

PO455 is a large evaporative fuel leak. A bad fuel cap is ONE of the things that COULD be the problem. Fuel system cleaning only lightened your wallet. Reading your post is confusing. Did all this start AFTER the Valvoline Wallet Flushing? If so , they left something loose or disconnected. I would find a qualified repair shop to fix the problem, and if it has anything to do with what Valvoline did, make them pay the bill.

go to autozone and get the codes. they will test for free.

Message Center Display
The following messages may be displayed on the message center.
This message center will display CHECK TRANSMISSION if the following codes have been set.


DTC Codes Possible Faults P1746, P1747, P1760 Electronic pressure control solenoid P0743, P1767 Torque converter clutch circuit P0750, P0755, P0760 Shift solenoid circuit P1714, P1715, P1716 ISIG P0731, P0732, P0733, P0734 SFT error P0741, P1742, P1743, P1744 Torque converter clutch error P1783 Over temperature P1700 NEV error P0712, P0713, P0710,
P1710, P1713, P1718 Transmission fluid
temperature error P0705, P0708, P1704 Transmission range sensor error P0500, P0503 Vehicle speed sensor error P0715 Turbine shaft speed error
NOTE: For codes. For additional information, refer to Diagnostic Trouble Code Chart.

you may be low on brake fluid or pads worn