Red security light on dash is blinking and engine won't start or even turn over.

It was a defective battery but led me on a merry chase.

Thanks for your post. I have same pickup. And sure enough it was the batt. All same symptoms. It was dying going down road after jumping in about 3 mins. Im sure cause it was keeping the constant amp rating to operate.

Same issue, It was the battery leads. Why have it on a security light indicator???? Anyways, thanks guys.

Same issue here. I removed the battery and in the process I noticed the connectors were corroded. I got the battery tested at a local auto parts store and was told that there were no indicators that it could be defective, but being that it had over 5 years powering the engine I was told that it would not be a bad idea to replace it with a new one. I put a new battery, new battery connectors and new batteries for the door remote, and "brrrm, brrrm" back to normal. One Note; before I installed the new battery I held the negative and positive battery connectors against each other for 15 seconds (no battery in the truck) to reset the computer. So far, not only the blinking red light on the dash board (Anti- Theft Security) stopped blinking, but also the engine light turned off and a miss-fire issue the truck was having (related to ignition coils failure) has also gone away. I wiil keep my fingers crossed, but so far (over 50 miles) my 2003 RAM 1500 is running smooth and feeling like new. I will update if anything changes within the next 1000 miles.