Can a OBD2 Scanner Clear Codes? What Really Gets Erased

Quick answer: Can a OBD2 scanner clear codes? Yes. Almost every scanner, even a basic code reader, has an Erase or Clear Codes function that deletes stored trouble codes and turns off the check engine light. But clearing is not a repair. It also wipes freeze frame data, resets your emissions readiness monitors, and the code returns if the fault is still there.

So yes, you can clear codes yourself. Whether you should, right now, is a different matter.

My rule: read, record, repair, then clear. In that order. When I see someone clear a code before writing it down, I wince, because any technician who looks at the car later starts from scratch, with no codes and no freeze frame snapshot to guide the diagnosis.

How to Use an OBD2 Scanner to Clear Codes

Exact menus vary by tool, so check your scanner’s manual. Autel’s AutoLink manual gives a typical sequence:

1. Turn the ignition off before plugging anything in. Autel warns not to connect or disconnect test equipment with the ignition on or the engine running.
2. Find the 16-pin diagnostic connector, usually under the dash on the driver’s side.
3. Plug in the scanner, then turn the ignition to ON.
4. Let the tool link. It cycles through OBD2 protocols until it finds the one your car uses.
5. Read the codes first and write down every one, plus the freeze frame data.
6. Choose Erase Codes. Autel says to do this with the key on and engine off, and not to start the engine during the erase.
7. Confirm, then turn the ignition off and unplug the tool.

If the tool shows a linking error instead, see our guide on why an OBD2 port is not communicating.

What Clearing Codes Also Erases

Honestly, this is the part most people miss. According to Autel’s manual, erasing can wipe:

• The stored trouble codes, obviously.
• Freeze frame data, the snapshot of engine conditions at the moment the fault was set.
• Manufacturer-specific enhanced data, on tools that read it.
• I/M readiness status. Every monitor resets to Not Ready or Not Complete.

That last point catches people out at inspection time. Emissions programs check readiness monitors, and a freshly cleared car usually shows several as incomplete.

Freeze frame data matters too. It shows the speed, temperature and load when the fault happened. Once it’s gone, a technician has less to work with.

Why Codes Come Back After Clearing

Here’s the decision tree I’d use when the light returns.

1. The fault is still there. Autel’s manual is blunt: as long as the vehicle has a fault, the codes keep coming back. Clearing only resets the memory.
2. It’s an intermittent fault. The car needs the right conditions to retest, so the light may stay off for days and then return.
3. The repair was incomplete. A new sensor on damaged wiring will set the same code again.
4. A permanent code is stored. See the next section.

If the same code returns after a repair, stop clearing it. Don’t fall into that loop. Clearing a code over and over just hides useful evidence.

Can a OBD2 Scanner Clear Codes Permanently?

No scan tool can delete permanent diagnostic trouble codes. California’s Bureau of Automotive Repair (BAR) explains that these PDTCs look like regular codes, but they can’t be erased with a scan tool or by disconnecting the battery.

Only the car’s own OBD2 system clears them, once it has verified the fault is gone. That means fixing the problem and then driving normally.

BAR’s smog test rules show how seriously regulators take this, and the numbers are specific. In California, 2010 and newer vehicles with a stored PDTC fail the Smog Check, unless the car has finished at least 15 warm-up cycles and 200 miles since its codes were last cleared.

What About Disconnecting the Battery?

It often clears codes too, but it’s a blunt tool. The California Air Resources Board says a dead, disconnected or replaced battery can leave readiness indicators incomplete, which can fail an emissions test.

I’d use the scanner instead. It’s cleaner. You keep a record.

When to Call a Technician

Get professional help, rather than clearing and hoping, if:

• The check engine light is flashing. CARB says that signals a malfunction that could damage your catalytic converter.
• The same code returns after you’ve repaired it.
• The code points to misfires, fuel trim or catalyst problems.
• An inspection is coming up and monitors won’t set.

For that last case, see OBD2 not ready for smog check. For misfire codes, our spark plugs vs fuel injectors guide helps narrow the cause. More scanner guides live in Diagnostics & Engine.

Frequently Asked Questions

Can an OBD2 Scanner Reset Codes?

Yes. “Reset,” “clear” and “erase” all mean the same function. It deletes stored codes and turns off the check engine light until the fault is detected again.

Will Clearing Codes Pass an Emissions Test?

Usually not right away. Clearing resets readiness monitors to incomplete. CARB says owners can often set them by driving normally for about a week.

What Is an OBD2 Scanner and Code Clearer?

It’s simply a scan tool that can both read and erase trouble codes. Most basic readers do both. More advanced tools add live data, freeze frame and manufacturer-specific systems.

Is It Bad to Clear Codes Without Fixing the Problem?

In my view it doesn’t damage anything, but it hides the evidence. Autel’s manual says not to erase codes until the system has been checked by a technician.

How Long After Clearing Codes Does the Light Come Back?

It depends on the fault. A hard fault can return on the next drive. An intermittent one may take several drive cycles.

Last updated: November 10, 2026. Sources: Autel AutoLink AL319 manual: erasing codes, California BAR: On-Board Diagnostic Test Reference (PDF) and CARB OBD II fact sheet.