Capture diagnostic evidence before clearing a fault code

01

Why save the evidence before clearing codes?

Clearing a fault code changes the evidence available for diagnosis. Bosch's OBD 1300 manual warns that its erase function resets emissions-monitor readiness and, depending on the vehicle, may also remove freeze-frame information and monitor-test results. Its erase command cannot remove permanent DTCs.[bosch-erase]

Save the starting evidence before deciding whether clearing is appropriate. This guide is a workshop recording checklist, not permission to clear a particular vehicle or a substitute for the manufacturer's diagnostic procedure.[bosch-erase]

02

1. Record the vehicle and the complaint separately

As a practical job-recording step, note the confirmed make, model, model year, engine or fuel type and market. Record the VIN in the workshop job record where appropriate, and confirm any uncertain vehicle details rather than guessing them.[bosch-codes]

Keep the customer's account separate from your observations. Record when the complaint happens: for example, during a cold start, after warming up or under a reported driving condition. Label these as reported conditions unless you have actually observed them. Bosch distinguishes generic from manufacturer-specific codes; a generic description alone does not establish the correct vehicle-specific test.[bosch-codes]

03

2. Save the complete code report and scan scope

Save or photograph the exact code strings, descriptions, reported status and the module name or address. Keep any additional suffix or failure-type information exactly as displayed. Bosch's Read Codes section explains that module identity and DTC type are separate information fields, and that not every vehicle supports every type.[bosch-codes]

For a useful handover, also note which systems were successfully read and which were not accessible. Do not turn an unread module into a clean result. A generic engine/emissions read does not establish that every vehicle system has been checked. These recording recommendations do not promise that a particular scanner can access every module.[bosch-codes]

04

3. Preserve freeze-frame data and readiness status

If available, save the freeze frame with its associated code and module. Record the values, units and operating conditions actually shown rather than filling gaps with expected numbers. Bosch describes freeze frame as a snapshot of operating conditions at an emissions-related fault; it is not the same as a live reading taken now.[bosch-freeze][bosch-erase]

Record the current readiness display before any erase operation. Bosch warns that clearing resets readiness and may remove other diagnostic information, depending on the vehicle. Missing or unsupported data should stay labelled unavailable; it is not evidence that the vehicle passed a test.[bosch-freeze][bosch-erase]

Do not use this general guide to select a drive cycle or judge inspection eligibility. Those decisions need the applicable vehicle instructions and local requirements.[bosch-freeze][bosch-erase]

05

4. Choose the next test before making a change

Use the code to guide investigation, not to name a confirmed failed part. Look up the full code and applicable manufacturer procedure for the confirmed vehicle. As an editorial diagnostic discipline, write down the hypothesis, the next test and what result would support or weaken it.[bosch-codes][bosch-erase]

If clearing becomes an appropriate step under that procedure, keep the original evidence and document the action separately. An erase acknowledgement or an immediately clear code list is not proof of repair. Bosch notes that a relevant monitor may need to run before a repair conclusion can be reached; it does not provide a universal drive cycle.[bosch-codes][bosch-erase]

06

Use MechNostic to organise the next step

Bring your confirmed vehicle details, symptom description and photos of fault-code displays into MechNostic to help organise the diagnostic discussion. The app supports text and photo input, including VIN-plate images; check the extracted details against the original rather than assuming they are correct.[mechnostic]

Keep reported symptoms, observed readings, possible causes and confirmed findings distinct. Use MechNostic's suggestions alongside actual scan evidence and current manufacturer service information. An AI suggestion is not a measured result, a repair specification or a confirmed diagnosis.[mechnostic]