# Accidentally jumper car incorrectly **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [June 27, 2019, 6:37am UTC](https://community.cartalk.com/t/accidentally-jumper-car-incorrectly/143094 "2019-06-27T06:37:12Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![iag360\_141684](https://avatars.discourse-cdn.com/v4/letter/i/df705f/32.png) [@iag360\_141684](https://community.cartalk.com/u/iag360_141684)\ **Post date:** [June 27, 2019, 6:37am UTC](https://community.cartalk.com/t/accidentally-jumper-car-incorrectly/143094/1 "2019-06-27T06:37:12Z")
2004 Kia amanti When jumping the car I accidentally put the positive on the negative terminal. This caused a bunch of sparks to appear with a nasty aroma. It happened for a good 2 1/2 seconds before I hurry and removed it. I drove it home and every thing seemed fine but I’m still worried. May I have caused some damage that I do no know of or could possibly encounter in the future because of this? ---
**Author:** ![COROLLAGUY1](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/corollaguy1/32/7575_2.png) [@COROLLAGUY1](https://community.cartalk.com/u/COROLLAGUY1)\ **Post date:** [June 27, 2019, 9:34am UTC](https://community.cartalk.com/t/accidentally-jumper-car-incorrectly/143094/2 "2019-06-27T09:34:02Z")
When a car battery is connected backward a fuse designed to protect vehicle electronics should blow. If your vehicle doesn’t have a fuse (almost all cars do) designed for this purpose, you will send electrical current backward through systems in your car including ECU, transmission control unit and more. If current flows backward through lights that’s not a problem. The issue is when current flows backward through an electronics that have diodes such as the ECU / ECM (Engine Control Unit / Module). It is not common to damage the Engine Control Unit / Module by connecting the battery cables incorrectly. Most of them are designed to withstand reverse polarity. In the worst case, the ECU/ECM can be removed and inspected if a diode has failed. ---
**Author:** ![Rod-Knox](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rod-Knox](https://community.cartalk.com/u/Rod-Knox)\ **Post date:** [June 27, 2019, 2:33pm UTC](https://community.cartalk.com/t/accidentally-jumper-car-incorrectly/143094/3 "2019-06-27T14:33:46Z")
When the key is off there is significantly less chance of damage when reversing the polarity compared to the key being on. But time will tell one way or the other.