Purpose of inspection
Inspect the condition of the ECU (input signal, output signal) when the malfunction occurs and determine the cause by checking the data of ECU.
• Freeze frame data
Freeze frame data is data of ECU when the diagnostic codes are recorded. Malfunctions are judged depending on whether the malfunction signal system is an open circuit or short circuit, based on the type of freeze frame data. Example: When the codes from the water temperature signal system are detected: Check the freeze frame data on the water temperature signal. If the temperature is -40 degrees centigrade, the malfunction can be judged to be an open circuit. If it is 200 degrees centigrade or more, the malfunction can be judged to be a short circuit.
• Freeze frame data is deleted when the diagnostic codes are cleared or the modes are switched. Therefore, check freeze frame data immediately after checking diagnostic codes.
• As for diagnosis detection, there is time lag between malfunction occurrence and detection. Therefore, it is not the data at the time of malfunction occurrence but the data after the time lag is stored in memory as a freeze frame data.
• By referring to the freeze frame data, it is possible to estimate to some degree, the running conditions at the time of the malfunction.
• ECU data
ECU conditions can be checked by using ECU data even if the diagnostic codes are not identifi ed. The auto trigger function makes it possible to automatically record the ECU data before and after the malfunction is found. The function to record ECU data on the hand-held tester (snap shot) makes it possible to analyze ECU data when the malfunction occurs. This function can locate malfunctions that the diagnostic codes do not output, including the wrong sensor range and actuator system malfunctions.
Inspection methods
Refer to the ECU data and determine what has greatly changed since the symptoms occurred or if something has an abnormal value.