Diagnostic trouble codes adapted to newlegal requirements
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Diagnostic trouble codes adapted to new
legal requirements
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Since 1988 Californian authorities (later followed by other countries around the
world) have required automotive manufacturers to make it possible through intelligence built
into the car's control system to detect and locate emission-related faults using OBDI
(On-Board Diagnostics).
For model year 1993 and later cars, the Californian requirements have been become
even stricter through the introduction of OBD II. One purpose of the new requirements was to
bring about the standardization of diagnostic trouble codes and command codes so that
different motor manufacturers will use the same codes, which will make life easier for
technicians who work on several different systems and makes of car. Recommendations for
this standardization are set forth in document SAE J-2012 (diagnostic trouble codes) and
document SAE J-1979 (command codes).
As a result of the above, the diagnostic trouble codes for the Saab Trionic system on
the 1994 model are different than those to which we have been accustomed when using the
ISAT scan tool for diagnostic trouble code reading.
The previous unique diagnostic trouble code for intermittent faults disappears
with the new diagnostic trouble codes. This does not mean that it is no longer possible to
detect intermittent faults, but intermittent faults are indicated in a different way than previously.
The new DTC consists of five characters, of which the first character is
a letter followed by a second part consisting of four digits (e g P0105). The letter indicates the
system as follows:
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B = Body
In addition there is also U (Undefined) as a spare.
The first digit after the letter indicates whether the code relates to legal requirements
according to the SAE (=0) or whether it is a unique manufacturer's code
(=1 or 2)
The second digit after the letter indicates the subsystem within the main group
concerned to which the diagnostic trouble code relates.
The meaning of the second digit for DTCs for Powertrains is as follows:
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P04xx Exhaust emission control system
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P05xx Speed/idling adjustment
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P06xx Electronic control module and its output signals
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P00xx Reserved for SAE
The last two digits in the diagnostic trouble code are a serial number which gives
each diagnostic trouble code in the group concerned a unique number.
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