ADAS & Vehicle Technology

Pre- and Post-Repair Scanning: What Every Vehicle Owner Should Know

Before a single panel is pulled or a single part is replaced, your vehicle should be telling the repair shop what’s wrong with it.

Not through visible damage — through data.

Modern vehicles store diagnostic trouble codes (DTCs) across dozens of electronic modules. After a collision, some of those codes point to problems you can see. Others point to problems you can’t — compromised ADAS sensors, malfunctioning restraint systems, damaged communication networks between modules. A comprehensive diagnostic scan reads all of them.

This scan needs to happen twice: once before the repair begins, and once after it’s complete. Both are essential. And both are routinely skipped.

What Is a Diagnostic Scan?

A diagnostic scan connects a scan tool to your vehicle’s onboard computer network and reads fault codes from every electronic module — not just the engine. A modern vehicle can have 80 or more individual control modules managing everything from the transmission to the airbags to the parking sensors.

When a collision occurs, the impact can affect any of these modules, their wiring, or the sensors they rely on. Some faults produce warning lights on your dashboard. Many do not. A diagnostic scan finds both kinds.

There’s an important distinction here: a basic code read — the kind you might get at an auto parts store — only checks the engine and emissions system. A proper collision diagnostic scan checks every module in the vehicle, including:

• Supplemental Restraint System (SRS) — Airbags, seatbelt pretensioners, crash sensors
• ADAS modules — Forward camera, radar, blind spot, parking assist
• Body control module — Lighting, power windows, locks, mirrors
• ABS / stability control — Wheel speed sensors, yaw sensors, steering angle
• Occupant detection — Seat weight sensors, passenger airbag status
• Communication networks — CAN bus integrity between modules

A full system scan produces a report showing every stored and pending fault code across the entire vehicle. That report is the starting point for a proper collision repair.

Why You Need a Pre-Repair Scan

The pre-repair scan — performed before any disassembly or repair work begins — establishes the baseline. It answers the question: what did the collision do to this vehicle’s electronic systems?

Without a pre-scan, the shop is guessing. They can see the dented fender and the broken headlight, but they can’t see the fault codes stored in the airbag module, the ADAS camera error logged when the windshield flexed on impact, or the blind spot sensor that lost communication when the rear quarter panel absorbed the hit.

The pre-scan also protects everyone involved:

• It protects you by documenting every collision-related fault so nothing gets missed during the repair.
• It protects the shop by creating a record of pre-existing conditions — codes that were present before they touched the vehicle.
• It protects the integrity of the claim by providing documented evidence of what the collision affected.

A pre-scan that reveals 14 fault codes across 6 modules tells a very different story than a repair estimate that only addresses body damage. And that story matters — for the repair, for the claim, and for your safety.

Why You Need a Post-Repair Scan

The post-repair scan confirms that the repair actually fixed everything the pre-scan identified — and didn’t introduce new problems.

Collision repair involves disconnecting and reconnecting electrical components, removing and reinstalling sensors, replacing modules, and sometimes reprogramming systems. Any of these steps can introduce new fault codes. Without a post-scan, there’s no way to verify that every system is functioning correctly before the vehicle goes back to the owner.

Think of it this way: the pre-scan is the diagnosis. The post-scan is the verification. Skipping either one is like a surgeon operating without imaging beforehand or discharging a patient without checking whether the surgery worked.

A clean post-scan — where all collision-related codes have been resolved and no new codes are present — is the only objective confirmation that the vehicle’s electronic systems are back to proper working order.

What the Manufacturers Require

This isn’t a matter of opinion or best practice. Every major vehicle manufacturer has published position statements requiring both pre- and post-repair diagnostic scanning after a collision.

These position statements are part of OEM repair procedures — the official, published instructions from the company that designed and built the vehicle. They carry significant weight because the manufacturer understands the vehicle’s systems better than anyone else.

The Inter-Industry Conference on Auto Collision Repair (I-CAR), the primary training organization for the collision repair industry, also emphasizes that scanning is a required step in the repair process — not an optional add-on.

When GM says scan the vehicle, and Ford says scan the vehicle, and Honda says scan the vehicle, and Subaru says scan the vehicle, and Toyota says scan the vehicle — there is no legitimate argument for skipping it. The people who engineered these systems are telling you, in writing, that scanning is mandatory.

What Happens When Scanning Is Skipped

When a shop skips the pre- and post-repair scans, the consequences aren’t theoretical. They’re real, and they’re dangerous.

Airbag systems may not function correctly. A stored fault in the supplemental restraint system could mean an airbag won’t deploy in your next collision — or will deploy when it shouldn’t. Seatbelt pretensioners that are supposed to tighten during impact may not fire. None of this triggers a dashboard light if the fault is in certain parts of the system.

ADAS features may misfire or fail to engage. A forward-facing camera that was knocked out of alignment by the collision might still appear functional — the lane departure icon still shows on your dashboard — but the system’s accuracy is compromised. Automatic emergency braking might activate too late. Or not at all.

Seatbelt pretensioners may malfunction. These devices use small explosive charges to cinch the seatbelt tight in a crash. If the system has an unresolved fault code, the pretensioner may not fire when you need it most.

All of this can happen without a single warning light on your dashboard. The vehicle looks repaired. It drives fine. But the safety net that’s supposed to protect you in your next emergency has holes in it that nobody checked for.

Why Scanning Gets Skipped

If scanning is this important — and every manufacturer requires it — why does it get skipped so often?

Three reasons:

1. The insurer doesn’t include it on the estimate. When the insurance company writes the initial repair estimate, they’re looking at photos of damage. Scanning isn’t visible damage. If the adjuster doesn’t include it, and the shop doesn’t push back, it doesn’t get done.

2. The shop doesn’t have the equipment or training. A proper full-system collision scan requires professional-grade scan tools — not the basic OBD-II readers used for engine diagnostics. Some shops, particularly those focused on volume over quality, may not invest in the right equipment or the training to use it properly.

3. Nobody asks for it. The vehicle owner doesn’t know scanning exists, so they don’t ask. The insurer benefits from keeping repair costs down, so they don’t volunteer it. And some shops just follow whatever the insurance estimate says, without supplementing for required procedures.

The result is a gap between what the manufacturer requires and what actually happens in the repair bay. That gap falls on the vehicle owner — both the safety risk and the financial impact.

How to Verify Your Shop Performed Scans

You have every right to ask for documentation. Here’s what to look for:

1. Ask for the pre-scan report before repairs begin. A reputable shop will show you the scan results and walk you through what the codes mean. If the shop says “we don’t scan” or “scanning isn’t necessary on this repair,” that’s a serious red flag.
2. Ask for the post-scan report at delivery. When you pick up your vehicle, request the post-scan report showing that all collision-related codes have been cleared and no new codes are present.
3. Check the repair invoice. Pre- and post-repair scanning should appear as separate line items on the invoice. If they’re not listed, ask why.
4. Look for calibration line items. If your vehicle has ADAS features and any related components were disturbed during the repair, you should also see calibration procedures listed. We’ll cover calibration in depth in our upcoming article on ADAS calibration.

A shop that performs proper scanning will have no problem showing you the documentation. A shop that gets defensive or dismissive when you ask is telling you something important.

What to Do If Your Insurer Refuses to Pay for Scanning

This happens more often than it should. You or your shop submit a supplement requesting payment for pre- and post-repair scanning, and the insurance company pushes back — claiming it’s not necessary, not supported, or included in other labor operations.

Here’s how to respond:

Cite OEM position statements. Every major manufacturer has published documentation requiring scanning. These are publicly available and carry significant weight in disputes. When the company that built the vehicle says scanning is mandatory, an insurance adjuster’s opinion to the contrary doesn’t hold up.

Reference I-CAR’s position. I-CAR has been clear that diagnostic scanning is a required part of the collision repair process. This isn’t a fringe opinion — it’s the industry training standard.

Document everything in writing. If the insurer verbally denies scanning, ask them to put the denial in writing and explain their technical basis for overriding the manufacturer’s repair procedures. Most adjusters will reconsider once they’re asked to document their position.

File a complaint if necessary. If your insurer refuses to pay for a procedure that the vehicle manufacturer requires, that refusal may constitute an unfair claims practice. Your state’s Department of Insurance accepts complaints, and documented denials of OEM-required procedures are exactly the kind of issue they take seriously.

You should never have to fight to get a required safety procedure covered. But if you do have to fight, the manufacturers, the training organizations, and the documentation are all on your side.

Scanning and Your Claim Value

Beyond the safety implications, scanning documentation directly affects the value of your insurance claim — whether you’re pursuing a repair supplement, a diminished value claim, or a total loss dispute.

A pre-scan report showing fault codes across multiple modules demonstrates the true scope and severity of the collision damage — often far beyond what’s visible on the surface. This documentation supports higher repair costs, stronger diminished value arguments, and a more complete picture of what the collision actually did to your vehicle.

Conversely, if scanning was never performed, you may have hidden damage that was never addressed — damage that affects both your safety and your vehicle’s value.

We Know What to Look For

At Collision Claims Advisors, we review repair documentation on every claim we handle. With over 25 years in the collision industry and IACP certification, we know what a proper repair looks like — and we know what’s missing when corners are cut. Scanning, calibration, and OEM procedure compliance are part of every evaluation we perform.

If you’re not sure whether your repair was done right, or if your insurer is pushing back on required procedures, we can help you understand your options and build a case based on what the evidence actually shows.

Get an Expert Claim Review

Don’t guess whether your repair was complete or your claim was handled fairly. Start your claim review here — it takes about 60 seconds, and there’s no cost or obligation. We’ll tell you exactly where you stand.