Steve-o

I have a 2003 c4s in need of a battery. My buddy says jump starting could blow out the ECU.
Comments?

IGROWL

I wouldn't think it would do any damage if you did it according to the manual. It says to start the process at the fuse box in the footwell. Do you have the manual? It walks you through step by step.

Dennis C

Follow the manual and you'll be fine. I've done it before with no issues.

Steve-o

Thanks for the quick replies. I'll give it a shot.

renaissance.man

Your buddy is right. You are risking damage to the ECU when jump starting. It is the initial spark that can be damaging. The same can be said about welding when the battery posts are connected, since you are essentially creating an electric short to ground.

Just b/c people do it and there are no obvious repercussions, doesn't change the fact that IT IS A RISK.

To be completely safe, remove both terminals from the battery posts first (isolating the sensitive electronics in the car), then hook up the jumper cables to just the battery. This is the safest way - sans a trickle charger.

As a matter of fact, I would refuse to give anyone a jump in any of my more modern cars for this reason. Replacing the ECU would be expensive and a hassle for sure,.

fpb111

Don't use the fuse box terminal to actually jump start the car. It is just there to enable you to open the frunk or engine lid to get to the battery (frunk) or jump start terminals in the engine bay, + terminal on right side and - the airbox bolt. See the manual!

Invius

FWIW, I've used mine to jump start another car and had no issues.