What are the signs of hidden damage after a car accident?

Consumer Reports says: "some damage from the fender bender may not be visible." It advises getting an estimate that covers recalibrating any affected sensors or cameras.

Consumer Reports says many newer cars have sensors for automatic emergency braking and adaptive cruise control behind the front bumper cover, and rear sensors can be affected too, even when the plastic shows no apparent damage. AAA says radar, camera and ultrasonic sensors may be "located in or behind the front and rear bumpers," and that even minor incidents can damage them.

Calibration means re-aiming a sensor so it reads correctly again. AAA says that after a sensor is replaced, the system must be calibrated, which "requires special training, tools and information." I-CAR calls post-repair calibration "a required step following the removal, installation, and/or repair of many safety and driver convenience system parts." Consumer Reports advises making sure the repair facility has the equipment for proper calibration.

A scan reads the car's computers for stored warning messages, called fault codes. I-CAR says a scan before repair is a step in damage analysis, used "to identify errors, faults, and/or damage." A scan after repair is a quality-control step, to make sure all codes related to the collision, or set during repair, are identified and cleared. If damage prevents the early scan, I-CAR says it should be done "as soon as repair progress allows it to be done safely."

Consumer Reports says: "the body filler and paint applied during a shoddy repair job can prevent the sensors from working properly."

These come from a Consumer Reports checklist for used-car buyers. It does not tie them to a crash, so treat each as a clue, not proof:

• misaligned panels or large gaps, which the checklist says can point to either sloppy factory assembly or shoddy repair work
• paint that does not match from panel to panel, and paint on the rubber seals around the hood and trunk lid if repainting is suspected
• kinks or large dents in structural parts such as the floor pan, which the checklist says usually indicate a past accident, and fresh undercoating that may hide recent structural repairs

This page cannot tell you what is or is not wrong with any car.

Consumer Reports says: "Larger repairs may warrant a second opinion."

• Was the car scanned for fault codes before and after the repair?
• Were sensors and cameras checked and recalibrated, and by whom?
• What was found once the damaged area was opened up?
• Should I consider a second opinion?
• What should I watch for in the next few weeks?