GUIDE / OBD-II
Save freeze-frame data before clearing
Freeze-frame data shows operating conditions when a fault was recorded. Save engine speed, load, coolant temperature, vehicle speed, fuel-system status and trims if available. A snapshot may relate to only one fault; it is not continuous recording. Clearing codes may remove it and reset readiness. Never operate a scanner while driving.
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Scan worksheet →Source-backed code explanations
Sources and interpretation
Read the meaning first, then follow the cited manufacturer pages. The explanations and vehicle-specific examples have different scopes; verify the exact application before using a repair instruction.
- 2000 Powertrain Control/Emissions Diagnosis — Villager OBDII, Description and Operation ↗
Ford Motor Company · PDF 14, 18
2000 Mercury Villager example: stored operating conditions at fault detection, scan-tool access and single-event priority/replacement behavior. Printed pages 1-14 and 1-18. Does not establish how many frames every modern control module supports.
- On-Board Diagnostic Hand-Held Scan Tool Technology — EPA420-R-00-017, October 2000 ↗
U.S. Environmental Protection Agency
Historical emissions scan-tool report, printed page 6: Mode 2 retrieves freeze-frame information; Mode 4 resets emissions diagnostic information including freeze frame and readiness. Background for preserving data before clearing, not validation of a current scanner or every module. Text edition has no PDF page anchors.