Pre Scan And Post Scan Report Checklist

A pre-scan and a post-scan only create a comparison record of vehicle condition around a repair. They document what supported systems reported before and after work; they do not, by themselves, prove roadworthiness or that every fault is gone.

Why scan before and after — documentation, not a verdict

Workshops and careful DIY owners use pre/post scan reports to show which DTCs and system results existed at each stage. Official diagnostic workflows describe auto-scanning supported systems and saving reports so conditions can be compared around a repair. That comparison is a record-keeping aid, not a certificate of success.

Pre-scan checklist

1. Record vehicle identity: make, model, year, engine, registration or VIN note, and mileage.
2. Note warning lamps and the customer or owner symptom in plain language.
3. Connect safely with ignition in the state your tool requires.
4. Run an auto scan or system-by-system scan of the modules your vehicle and tool actually support.
5. Save the DTC list, freeze-frame where available, and the full report file or clear photographs.
6. Do not clear codes yet — diagnose and plan the repair first.

Auto scan detects supported systems; it does not imply every module or function is covered on every vehicle. Confirm coverage when a system is missing from the report.

Repair boundary: diagnose and fix before clearing

Clearing codes merely to make pre- and post-reports match destroys evidence and can hide an incomplete repair. Keep the pre-scan untouched as your baseline. Perform diagnosis and the required repair, then move to the post-scan. This article is a documentation checklist, not a repair manual — keep repair methods out of scope here.

Post-scan checklist

1. Repeat comparable conditions where practical (similar ignition state, temperature window and, if relevant, a comparable short road route).
2. Rescan the same supported systems you captured before the repair.
3. Save a new report with date, mileage and technician or owner initials.
4. Compare code lists, statuses and freeze-frame side by side.
5. Note any remaining pending, stored or permanent statuses without forcing a clear to “tidy” the paperwork.

What a clean report cannot prove — and when to escalate

A post-scan with no codes is not proof of roadworthiness, MOT success or a complete repair. Intermittent faults can sleep. Unsupported modules never appear. Road testing and professional inspection remain necessary when symptoms persist, safety lamps return, or the comparison raises new questions.

Escalate when reports disagree with the road feel, when communication fails on a system that should be present, or when legal or insurer documentation needs a qualified workshop stamp — use confirmed details record-keeping duties that this checklist does not create.

Next step and FAQ

If you need a handheld that can auto-scan supported systems and save reports for comparison, review the TOPDON ArtiDiag600S 4-system car code reader and confirm vehicle coverage first. Related reading: how to check car-scanner compatibility by vehicle and function and 4-system OBD2 scanner for dashboard lights.

Is a blank post-scan a pass?

No. It only shows that supported systems reported no codes under the conditions of that scan.

Should I clear codes so the reports match?

No. Clear only after the required repair, and never solely to tidy paperwork.

Why might a system be missing from the report?

Auto scan covers supported systems for that vehicle/tool pairing. Missing modules can mean lack of support, a connection issue or a vehicle-specific limit — verify officially.

Do I need a road test after a clean post-scan?

If symptoms were road-dependent or safety-related, a careful road check and, where needed, professional follow-up remain sensible.