Battery won't stay charged

First make sure the battery is fully charged. Also make sure the belt on the alternator is not broken/missing. after you charge the battery,start the vehicle and put a voltage meter/multimeter on volts dc and apply the leads to the battery posts,you should see anywhere from 13-14.5 volts from the alternator if it is working. if not,check the fuse or fuses for the alternator. if the fuse is good,replace the alternator,and test the battery.

you have a SHORTED, CONDITION, you need to inspect all wires within this circuit, including all grounds. are all your connections right ? with engine running is your battery showing 12 to 14 volts, is your starter connected properly, reinspect all wiring in this cicuit, are your battery cables in good shape ? make sure no other wires are touching wires in this charging circuit . have a parts store check the charging circuit for you . have them check the battery, and the alternator, one dead cell in battery can cause your problem, also even a new alternator can be bad !!!

CHECK WIRING THIS UNIT WILL CONTORT THE FIELD IN THE COMPUTER. THE FIELD CONTROL IS WHAT MAKES IT CHARGE.

Sounds very much like the battery or the battery cables/connections. If the battery has low fluid or a shorted cell or two, it won't take a full charge no matter how long you charge it.
If you are not able to take the battery in for a load test and validate that it is good, try changing it out with the battery in another vehicle that is not having a problem, and see if that vehicle suddenly develops the same issue. Batteries need to have a load applied while the voltage is checked for a valid determination of it's condition. If you have a volt meter, have someone try the starter while you are checking the battery voltage. If it falls way below 12 volts (replace it), or stays above 12 volts (good) you have a valid answer either way.

Sounds like a bad alternator. Drained your battery and when you turned on the lights it took all the power left in your battery. When you drain a battery down that far, they are real hard to jump, and coupled with the alternator, the car is not producing enough current to start and stay running.

I would take the alternator off and take it to oyur local auto parts store to be tested. If bad, replace it and charge the battery fully before starting. Then check voltage at battery with motor running. Should be 13.2 -14 Volts DC. If not, you may have a bad battery cable or blown fusible link. (especially that if the alternator tests good).....Mike

COULD BE PROBLEM IN THE ALTERNATOR.BATTERY COULD BE DRAINING THROUGH IT.TURN OFF RADIO.BEFORE DISCONNECTING BATTERY CABLES.TAKE OUT ALTERNATOR HAVE IT CHECKED.

CODE 43 IS ELECTRONIC SPARK CONTROL -.KNOCK SENSOR.LOOKS LIKE ALTERNATOR NOT PUTTING OUT ENOUGH VOLTS TO CHARGE BATTERY.YOU NEED 13.5 TO 14.5 VOLTS.CHECK ALTERNATOR FUSE AND ELECTRICAL WIRES.MAKE SURE BELTS NOT SLIPPING.IF ALL IS GOOD.REMOVE ALTERNATOR.LET AUTO ZONE CHECK IT.TO MAKE SURE.TURN OFF RADIO BEFORE MOVING BATTERY CABLES.SO YOU WONT LOSE RADIO CODE.YOUR CAR IS NOT GOING TO RUN RIGHT IF THE ECM DONT RECEIVE 12 VOLTS OR 13 VOLTS.

You need more than 12 volts to charge the battery. How many amps does the alternator put out? This is what charges the battery.

Replace the starter relay,It is located in the fuse box under the hood

Since you bench tested the alternator, and the battery has good capacity (hopefully isn't 5 years old or more), the next logical step is to do a leakage test.

Disconnect one of the battery cables (either one, I'd go with the negative one) and insert a 12 volt test light between the battery and ground of your car. Now, any current draw must go through the lamp. If it is lit with "nothing drawing any current" you can now look further for the offending circuit. Usually simple stuff like aftermarket alarm system, trunk light staying on, that sort of thing.

Even try removing fuses one at a time to localize which circuit to check.

Good luck.