2003 Chevrolet Malibutheft light comes on, won't start do you have any suggestions

What left light? The left headlight? That is weird.

Perhaps u have an electrical problem, but first make sure that some anti-theft program has not activated itself & disabled the vehicle. That recently happened to me. l actually called the AAA battery service out & when he arrived, the thing just started right up for him. Embarrasing.

Also check ur fuses.

Edit: Oh the THEFT light, in that case ur security system kicked in for some reason & disabled ur vehicle, which is what happened to me about two weeks ago. Has not happened again thankfully. Sometimes that just happens but if it happens a few times, ur ignition system is failing & will need to be replaced OR ur key may need to be replaced.

my mali did that too. Check the fuel pump.

Check the starter. Our van did that a few months ago, it ran fine then one night while we were out it just didnt start and the theft light was on. It was the starter. - Is it making any noise or trying to turn over when you try to start it?

take the positive battery terminal off the battery, & tap it to any grounded location(like any exposed bare metal) for 5 seconds DO NOT TAP IT TO THE OTHER SIDE OF THE BATTERY!!!!!(you'lll drain the battery & it wont start without a jump)
but the terminal back on the battery(MAKE SURE BOTH TERMINALS ARE ON TIGHT) & attempt to start ur car. Drive to the nearest service station.
if that does not work, next try getting a jump.
if the car wo not start, call a tow truck & have it taken a service station, This is a common thing for this car from 98 on up
but l do not believe Chevy has put out a recall

The theft light is caused by an ignition problem in the steering column. You need to get it replaced.

1. Turn key to on. do not try to start
2. Leave key on until theft light flashes. may take 10 min.
3. Key off for 5 seconds.
4. Repete.
5. Do this cycle 3 times. should relearn key?
6. Start vehichle.