6 | OBD 100 | All you need to know about OBD
All you need to know about OBD | OBD 100 | 7
569624 Rev "A"
2013-12-19
|
Robert Bosch GmbH
en
4.5
What are trouble codes
The OBD trouble codes (DTC) are defined in
SAE J2012 and ISO 15031-6. Manufacturer-
specific trouble codes can be defined by vehicle
manufacturers.
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.
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A plain language text outlining the cause of
the problem can be assigned to each trouble
code.
4.5.1
Trouble code structure
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The structure of the trouble codes is shown in
the following table. This information facilitates
trouble-shooting in situations for which no
trouble code description is provided.
Trouble codes are 5-position codes.
Example:
P 0 1 22 Throttle position sensor signal too low
Pos.
Value
Description
1
B
C
P
U
Body
Chassis
Powertrain
Network
2
Example
for P
0, 2
1
3
Trouble code defined by ISO / SAE
Trouble code defined by
manufacturer
Trouble code defined by ISO / SAE
or by manufacturer
3
Example
for P0
0 – F
0 – 2
3
4
5
6
7 – 9
A – C
D – F
Grouped by systems
Fuel air metering
Ignition system
Auxiliary emission controls
Vehicle speed and idle control
Computer and output signals
Transmission
Hybrid
Reserved for ISO / SAE
4, 5
00 – 99 Identification of individual
components
Tab. 3: Trouble code structure
4.5.2
Stored trouble codes
Stored trouble codes (DTC) are trouble codes
which have been stored in the electronic control
unit (ECU). The description of the trouble
code and the number of the electronic control
unit with the designation of its origin are also
displayed.
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If a trouble code has been set which causes
the malfunction indicator light (MIL) to come
on, the electronic control unit stores the
current values of the sensors at the time at
which the fault occurred.
4.5.3
Pending code (Pnd)
The first time a fault occurs this is stored
as a pending code in the fault memory. If a
pending code is confirmed in the second drive
cycle, it becomes a confirmed code. A pending
code stored in the electronic control unit is
automatically erased after 40 drive cycles
if the prevailing operating conditions were
the same as when the trouble code was set.
Otherwise the pending code is erased after
80 engine cycles. Such trouble codes report
those faults which have occurred during a drive
cycle but which were not sufficient to cause a
trouble code to be stored, i.e. not causing the
malfunction indicator light to come on.
4.5.4
Confirmed code (Cnf)
If a pending code is confirmed in the second
drive cycle, it becomes a confirmed code and
the malfunction indicator light comes on.
4.5.5
Permanent code (Prm)
Permanent codes are a special form of confirmed
codes. Permanent codes have only been set by
vehicles since 2010, which means that they are
not supported by all vehicles.
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Permanent codes cannot be erased with a
diagnostic tester or by disconnecting the
battery voltage. The problem must have been
rectified and must not have occurred again for
the trouble code to be automatically deleted
from the fault memory by the electronic control
unit.
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The presence of a permanent code will cause
the vehicle to fail an Inspection or exhaust
emission test.