14 | OBD 100 | Glossary
Glossary | OBD 100 | 15
569624 Rev "A"
2013-12-19
|
Robert Bosch GmbH
en
8. Glossary
Cnf
Confirmed code
If a pending code is confirmed in the second
drive cycle, it becomes a confirmed code and
the malfunction indicator light (MIL) comes on.
DTC
Diagnostic trouble code
A trouble code is a 5-position code made up of
a letter and four digits. A distinction is made
between standard trouble codes which may
occur with all vehicle makes and manufacturer-
specific trouble codes specified by vehicle
manufacturers for certain vehicle models.
A plain language text outlining the cause of the
problem can be assigned to each trouble code.
ECU Electronic control unit
EOBD European On-Board diagnosis
EOBD is not an official term but is often used to
refer to OBD-2 in conjunction with EU vehicles.
For further information refer to Section 4.1.
Drive cycle
A drive cycle commences on starting the engine
(warm or cold) and ends on switching off the
engine.
Freeze frame data (FFD)
The following data (freeze frame data) are
stored in connection with the first pending
code:
R
Vehicle speed
R
Coolant temperature
R
Intake manifold pressure
R
Engine load
R
Mixture formation adaptation value
R
Lambda control status (control loop)
R
Time since trouble first recorded
The data represent a sort of snapshot of the
prevailing operating and ambient conditions at
the moment in time at which the trouble was
detected. A freeze frame data set remains stored
in the memory even if another emission-related
trouble code is stored (this does not however
apply to trouble codes resulting from misfiring
or faults in the fuel system). Freeze frame data
stored for a trouble code arising from misfiring
or a fuel system fault overwrite all previously
stored data and cannot be overwritten
themselves.
I/M monitors
The Readiness code is used in OBD to refer
to the testing of emission-related functions.
Since the introduction of OBD-2 all electrical
components have been continuously checked for
proper operation. In addition, complete systems
(e.g. exhaust gas recirculation) are checked
by way of diagnostic routines which are not
constantly active. The Readiness code is set as
a means of checking whether these diagnostic
routines have been performed.
The Readiness code gives an indication of
whether a diagnosis result has been supplied
for all individual systems since the fault memory
was last erased or the electronic control unit
was replaced.
The following are permanently monitored:
R
Missing combustion
R
Fuel system (injection times)
R
Circuits for emission-related components
The following are monitored once per drive
cycle:
R
Lambda sensor function
R
Catalytic converter function
If the functions of systems and components
are tied to certain operating conditions, these
are only checked on passing the corresponding
operating points (speed, load or temperature
thresholds).
i
The Readiness code was introduced as a
means of revealing manipulation. It makes
it possible to see whether the fault memory
was erased by disconnecting the battery for
example.