Chapa Lab · MotorAUTOCODES
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Comprenez l’alerte avant de changer des pièces

Votre voiture parle en codes.
Ici, on les comprend.

Comprenez les codes OBD-II et les voyants, leurs causes possibles, les contrôles sûrs et quand arrêter de conduire. Consultez le VIN et les rappels officiels sur demande.

OBD-II / LIVEA clear clue before replacing a part
Lire mon alerte Ne remplace pas le diagnostic d’un garage. Il vous aide d’abord à comprendre et décider.

AUTO / DIAG 01

Que voulez-vous vérifier ?

Try:
P0420

Guidance, not diagnosis

Catalyst system efficiency below threshold

Priority medium

The control module compares signals before and after the catalyst and sees less exhaust cleaning than expected. This code alone does not prove the catalyst must be replaced.

Possible causes

  1. 01Exhaust leak
  2. 02Aged or unstable oxygen sensor
  3. 03Degraded catalyst
  4. 04Incorrect mixture or combustion

Safe checks

  • Check related mixture or misfire codes.
  • Inspect for leaks only when the exhaust is cold.
  • Compare sensor data before replacing parts.

A code is a clue; it does not prove that one particular part has failed.

STEP 01

Read the warning

Enter the reader code, dashboard light or vehicle data.

STEP 02

Understand the scope

Separate meaning, possible causes and safety signals without false certainty.

STEP 03

Decide with context

Save or print a clear sheet before speaking with a workshop or replacing parts.

For people, not control modules

More context before opening the toolbox.

Buying a used car?

Check the VIN and review general safety campaigns before deciding.

Did a warning light appear?

Tell a routine service need from a signal that requires a safe stop.

Speaking with a workshop?

Bring a printable sheet with the code, symptoms and useful questions.

Clean-workshop privacy

No account. No vehicle history. No stored VIN.

Local explanations run in your browser. VIN and recall requests go to NHTSA only when you ask. Advertising is prepared for the future but remains disabled in this draft.

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