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44
Figure 4-22 DTC & FFD Screen
Stored Codes
Stored codes are the current emissions-related DTCs from the ECU of the vehicle.
OBDII/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 DTCs may vary by vehicle.
Pending Codes
These are codes that were generated during the last drive cycle, but before the
DTC actually sets, two or more consecutive drive cycles are needed. 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 drive 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 do not necessarily indicate a faulty component or system.
If test results indicate another failure after additional driving, a DTC is stored to
indicate a faulty component or system.
Freeze Frame
Typically, the stored freeze frame is the last DTC reported. Certain DTCs that have
a greater impact on vehicle emission, have a higher priority. In these cases, the top
prioritized DTC is the one for which the freeze frame records are retained. Freeze
frame data includes a “snapshot” of critical parameter values at the time the DTC is
set.
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