cavatica

My daughter's 2012 Fusion Hybrid has started showing both the "Check brake system" and "Service AdvanceTrac" warnings. The first time, a little over a week ago, she was on the road and stopping for a stop sign when they went on. She said the brakes stopped working, as in she had to use the emergency brake to stop. From what I read above, she probably had some braking ability if she'd pressed the pedal hard enough. Fortunately, she was going slowly on a quiet side street, there was nobody around, and she stopped without incident. The lights went off after she restarted the car, and the next day we took it in to a Ford dealer. They checked out the mechanical parts, couldn't find anything wrong, drove the car around with the intent of recreating the issue and couldn't. Charged us $100-plus for the diagnosis, and said if it happened again we would need to replace a module which would cost something like $1600 for the part and another $400 for the service. (I assume that's the ABS module.) Anyway, the car lasted for a week before the lights went on again. She was just starting it up in the driveway. Turning the car off and on didn't clear the warnings. I don't have a lot of confidence in this dealer. It sounds like they want to gouge us for a part that should cost around $500, and their labor's no bargain either. $2000 is more than half the value of the car at this point, so maybe they're hoping we'll buy a new Ford and trade in the old one for pennies...good luck with that. I think I should take the car to an independent mechanic I trust and just have him do the replacement; what is the argument for bringing the car back to the dealer?