48
function can be applied by tapping the functional button at the lower bottom of the
screen.
Figure 4-18
Sample DTC & FFD Screen
Stored Codes
Stored codes are the current emission related DTCs from the ECM of the vehicle.
OBD II/EOBD Codes have a priority according to their emission severity, with
higher priority codes overwriting lower priority codes. The priority of the code
determines the illumination of the MIL and the codes erase procedure.
Manufacturers rank codes differently, so expect to see differences between makes.
Pending Codes
These are codes whose setting conditions were met during the last drive cycle, but
need to be met on two or more consecutive drive cycles before the DTC actually
sets. The intended use of this service is to assist the service technician after a
vehicle repair and after clearing diagnostic information, by reporting test results
after a single driving cycle.
a) If a test failed during the driving cycle, the DTC associated with that test is
reported. If the pending fault does not occur again within 40 to 80 warm-up
cycles, the fault is automatically cleared from memory.
b) Test results reported by this service do not necessarily indicate a faulty
component or system. If test results indicate another failure after additional
driving, then a DTC is set to indicate a faulty component or system, and the
MIL is illuminated.
Freeze Frame
In most cases the stored frame is the last DTC that occurred. Certain DTCs, those
that have a greater impact on vehicle emission, have a higher priority. In these
cases, the highest priority DTC is the one for which the freeze frame records are
retained. Freeze frame data includes a
“snapshot” of critical parameter values at