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Professional 909X User Manual
2.3 Diagnostic Trouble Codes (DTCs)
OBD II Diagnostic Trouble Codes are codes that are stored by the on-board
computer diagnostic system in response to a problem found in the vehicle. These
codes identify a particular problem area and are intended to provide you with a
guide as to where a fault might be occurring within a vehicle. DO NOT replace
parts based only on DTCs without rst consulting the vehicle’s service manual
for proper testing procedures for that particular system, circuit or component.
OBD II Diagnostic Trouble Codes consist of a ve-digit alphanumeric code.
• The 1st character is a letter (B, C, P or U). It identifies the “main system”
where the fault occurred (Body, Chassis, Powertrain, or Network).
• The 2nd character is a numeric digit (0 thru 3). It identies the “type” of code
(Generic or Manufacturer-Specic).
Note: Generic DTCs are codes that are used by all vehicle
manufacturers. The standards for generic DTCs, as well as their
denitions, are set by the Society of Automotive Engineers (SAE).
Manufacturer-Specific DTCs are codes that are controlled by the
vehicle manufacturers. The Federal Government does not require
vehicle manufacturers to go beyond the standardized generic DTCs in
order to comply with the new OBD II emissions standards. However,
manufacturers are free to expand beyond the standardized codes to make
their systems easier to diagnose.
• The 3rd character is a letter or a numeric digit (0 thru 9, A thru F). It identies
the specic system or sub-system where the problem is located.
• The 4th and 5th characters are letters or numeric digits (0 thru 9, A thru F).
They identify the section of the system that is malfunctioning.
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