What are a pre-scan and post-scan in ADAS calibration?

What is a pre scan on a car — and a post-scan

The two scans bracket the calibration so the result is provable, not assumed.

1. 1

   Pre-scan before the work

   The scan tool reads every relevant module and records existing fault codes, so anything already wrong is documented before the glass or the camera is touched.

2. 2

   Calibration

   The camera is calibrated — static, dynamic, or both — following the manufacturer procedure for the vehicle.

3. 3

   Post-scan after the work

   The scan tool reads the modules again, confirming the calibration passed and that no new fault codes appeared during the job.

4. 4

   Documentation

   The before and after results are recorded, so there is a record the camera was verified and the systems were clear when the car left.

Is a post scan necessary

The post-scan is what turns a calibration from an assumption into a proof. Without it, the shop is saying the camera was calibrated; with it, the shop is showing the scan results that confirm it. The post-scan catches fault codes that a test drive would not — a camera that calibrated on the targets but throws a code on the road, or a related module that lost its settings during a battery disconnect.

The pre-scan matters just as much. Vehicles carry fault codes from all kinds of unrelated issues — a tire pressure sensor, an old airbag code, a parking sensor glitch. The pre-scan records those up front so they are not later blamed on the windshield replacement, and so the technician knows which codes are new and which were already there.

What the scans catch

• Existing fault codes documented before the work, so they are not blamed on the replacement.
• A calibration that did not pass — caught on the post-scan, not on the road.
• Related modules that lost settings during a battery disconnect or reconnection.
• A clear record that the camera was verified and the systems were clean when the car left.

More questions about pre- and post-scans