A useful before-and-after scan shows what changed. Record the vehicle, symptoms, modules reached and exact fault messages before repair. Afterward, repeat the relevant checks and document any remaining faults or unavailable modules. A clean code list alone does not prove the original problem is fixed.
A warning light disappears after work on a car. That is encouraging, but it leaves two questions: did the original fault stay away, and did the tool reach the same systems on both scans? A simple comparison record makes those questions easier to answer.
This guide provides a checklist you can use with a compatible full-system scanner. It also explains when our EDIAG C1 is a sensible choice for that workflow.
Start with the systems you need to check
Generic OBD-II diagnostics focus on emissions-related information. A full-system diagnostic tool can also access supported manufacturer-specific systems, such as braking, transmission or body electronics. The systems actually available depend on the vehicle and the tool’s software.
Check the expected module coverage before buying. “Full system” does not mean every controller on every car, and an unavailable module is not the same result as a module reporting no faults. TOPDON’s diagnostic manual makes this distinction through supported-system scanning and vehicle-dependent functions; its menu instructions apply to that tool, not to C1.
Save a baseline before clearing anything
Give the record a recognizable name: vehicle identifier, date and “before repair.” Use the tool’s available records or screenshots, supplemented by written notes. The aim is to preserve what you actually saw, regardless of the app’s export features.
| Record | What to capture | Why it matters |
|---|---|---|
| Vehicle and visit | Year, make, model, engine, mileage and date. Keep a full VIN in your private records. | Prevents comparisons with a different vehicle or visit. |
| Original complaint | The symptom, warning lights and conditions when it happens. | Keeps the repair focused on the problem the driver experienced. |
| Scan coverage | Modules reached, modules unavailable and any connection messages. | Shows whether the two scans cover the same ground. |
| Fault details | Module name, exact code, description and displayed status. Save associated data if available. | A code count loses the context needed for comparison. |
| Test conditions | Ignition or engine state and any relevant conditions required by the service procedure. | Makes a later comparison easier to interpret. |
Do not replace the original record with a screenshot taken after clearing codes. If a procedure calls for clearing, note when it happened. For an introduction to code descriptions and statuses, use our OBD2 code reader guide.
Compare the same evidence after repair
- 1. IdentifyConfirm the same vehicle and software selection.
- 2. RepeatRescan the supported systems relevant to the job.
- 3. CompareMatch module names, codes and statuses against the baseline.
- 4. VerifyRecord the symptom check and any work still needed.
Make a separate note of the repair performed. If the vehicle’s procedure requires a relearn, calibration or a particular verification condition, record whether it was completed. A rescan supports repair verification; it does not replace those steps or a physical inspection.
| After-repair finding | Useful next record |
|---|---|
| Original code remains | Save its current status and the conditions of the rescan; continue the vehicle-specific diagnostic procedure. |
| A different code appears | Document it separately and investigate its relationship to the work. Timing alone does not establish the cause. |
| No codes, but the symptom remains | Record that the complaint is unresolved. Do not close the job on the code result alone. |
| A previously reached module is unavailable | Mark the comparison incomplete and investigate communication or test conditions. |
| No relevant codes and the symptom check passes | Record the actual checks completed and conditions observed, without claiming every possible fault is ruled out. |
Keep both diagnostic reports: EDIAG C1 can generate pre-repair and post-repair reports. Save both with the vehicle’s service record and compare the scan results to see what changed. Add a brief note about the work performed, the symptom check and any follow-up needed.
When EDIAG C1 fits this workflow
We recommend considering C1 when you want a compact Bluetooth adapter for supported full-system diagnostics through a mobile app. Its listed AutoVIN and manual vehicle selection options help you start with the correct vehicle profile; verify that profile before scanning.
Start with our vehicle coverage information, then ask about your exact year, model, engine and required modules. If your work requires a dedicated tablet, specific report exports or functions beyond C1’s documented capabilities, make those requirements part of the comparison before choosing a tool.
Common questions
Do I need full-system scanning for every check-engine light?
It depends on the diagnostic job. Basic emissions information may answer an initial question, while faults or symptoms involving other controllers require appropriate system access. Choose coverage around the systems you need to investigate.
Does a post-repair scan prove a car is fixed?
No. It records the diagnostic results available at that time. Repair verification also needs the relevant symptom check and any vehicle-specific tests or procedures.
Can I use this checklist without PDF export?
Yes. Screenshots and a clearly labeled written comparison can preserve your own observations. If a workshop or customer requires a formal report format, verify that feature separately before purchase.
Does C1 scan every module on every vehicle?
No universal coverage is promised. C1 lists full-system diagnostics, but module and function availability must be confirmed for the exact vehicle.
Keep the before record, compare the same systems, and document what you verified. If C1 covers the modules your vehicle needs, it offers a compact way to support that routine.
Sources & further reading
- EDIAG C1: current product features and software terms
- TOPDON ArtiDiag900 Lite manual: supported systems and before/after scan comparison
Product information and sources checked September 16, 2026. This EDIAGTOOL buying guide is based on published documentation, not a hands-on vehicle test. Follow service information for your exact vehicle.
