Record all freeze frame data before disconnecting any connectors or clearing code(s). When DTCs are cleared, the Freeze Frame data which may help diagnosed an intermittent fault will also be erased from ECM’s memory.

Freeze Frame Data: The Freeze Frame function is designed to provide technicians with engine and vehicle information at the time a code is set. Freeze Frame can be thought of as a snapshot of certain operating conditions present at the time the MIL is turned on and a code set. Because this data is critical to determining the cause of a malfunction, this particular data is locked into a Freeze Frame Data memory location. If more than one DTC is encountered, the first one detected will have Freeze Frame Data available.

Readiness Test “Incomplete” message indicates the ECM has not tested a system. If a customer complaint is present at the time of repair, it is important to run (“complete”) of the readiness tests. If a vehicle has DTC, some readiness tests will not complete since some electrical problems will make it impossible for the ECM to monitor signals during system operation. Run all the OBD monitors to get suitable readiness tests to ‘complete’ after repair the system.