Enhanced Diagnostics

Enhanced diagnostic information, found in the CODE HISTORY function of the TECH-1, is designed to provide the service technician with specific malfunction occurrence information. For each of the first five and the very last Diagnostic Trouble Codes (DTCs) stored, data stored to identify the specific DTC, the number of occurrences and the number of drive cycles since the malfunction first and last occurred. A normal drive cycle consists of starting the engine, driving the vehicle over 8 km/h (5 mph) and keying down. These first five DTCs are also stored in the order of occurrence. The order in which the first five DTCs occurred can be useful in determining if a previous malfunction is linked to the most recent malfunction, such as an intermittent open in a wheel speed sensor circuit which later becomes completely open. However, if a malfunction is present, the drive cycle counter will increase by turning the ignition switch to "ON" and "LOCK."

During difficult diagnosis situations, this information can be used to identify malfunction occurrence trends. Does the malfunction occur more frequently now than it did during the last customer visit? Did the malfunction only occur once over a large number of driving cycles, indicating an unusual condition present when it occurred? Does the malfunction occur infrequently over a large number of drive cycles, indicating that special diagnosis techniques may be required to identify the source of the malfunction? If, for example, a malfunction occurred one out of 20 drive cycles, the malfunction is intermittent and has not recurred for 19 drive cycles. This malfunction may be difficult or impossible to duplicate and may have been caused by a severe vehicle impact (large pot hole, speed bump at high speed, etc.) that momentarily opened an electrical connector or caused unusual vehicle suspension movement. Problem resolution is unlikely, and the problem may never recur (check diagnostic aids provided for that DTC). If, for example, the malfunction occurred three out of 15 drive cycles, the odds of finding the cause are still not good, but you know how often it occurs and you can determine whether or not the malfunction is becoming more frequent based on an additional or past customer visit if the source of the problem cannot or could not be found. If the malfunction occurred 10 out of 20 drive cycles, the odds of finding the cause are very good.

By using the additional malfunction data, you can also determine if a malfunction is randomly intermittent or if it has not recurred for long periods of time due to weather changes or a repair prior to this visit. Say a DTC occurred 10 out of 20 drive cycles but has not recurred for 10 drive cycles. This means the malfunction occurred 10 out 10 drive cycles but has not reoccurred since. A significant environmental change or repair may have occurred 10 drive cycles ago. A repair may not be necessary if customer information can confirm a recent repair. If no repair was made, the service technician can focus on diagnosis techniques used to locate difficult-to-recreate problems.