Diagnostic trouble codes (DTCs)

If the control module detects a fault it stores a diagnostic trouble code (DTC) and the SRS indicator lamp lights light lights. The only time the warning lamp does not light is when the cable between the control module and combined instrument panel is short-circuited to ground or if the bulb is blown. When the ignition is switched on the lamp should light for approximately 3 seconds and then go out if no diagnostic trouble code (DTC) is stored. The control module can store up to 10 diagnostic trouble codes (DTCs). If for some reason a fault disappears after the diagnostic trouble code (DTC) has been permanently stored in the control module, information about the fault remains in the control module.

Each diagnostic trouble code (DTC) has 4 fault clocks which store data about the start time and, if applicable, the end time for the fault. Absolute start and end times are related to the total time that the system has been powered up. Relative start and end time displays the time the fault occurred or disappeared the last time the ignition was switched on. The absolute time displays the days and the relative time displays the hours, minutes and seconds. If the fault recurs, the end time is rest and the fault code counter (counter 2) counts up by one.

Each diagnostic trouble code (DTC) also has a counter (counter 1) which displays whether the fault is active (permanent) or passive (intermittent). If the counter value is 0 the fault is intermittent. The counter is used during fault-tracing to check if the fault has disappeared or if it remains. The diagnostic trouble code (DTC) status row is updated continuously and switches to intermittent fault if the fault becomes inactive. However, if the fault was passive, but then changes to active, the fault code status row changes to permanent fault.