Equus 3130 - Scan Tool – OBD2 - Manual (Page 17)

OBD2 15
E
Onboard Diagnostics
DIAGNOSTIC TROUBLE CODES (DTCs)
DIAGNOSTIC TROUBLE CODES (DTCs)
Diagnostic Trouble Codes (DTCs) are
meant to guide you to the proper serv-
ice procedure in the vehicle’s service
manual. DO NOT replace parts based
only on DTCs without first consulting
the vehicle’s service manual for prop-
er testing procedures for that particular
system, circuit or component.
DTCs are alphanumeric codes that are used to identify a
problem that is present in any of the systems that are mon-
itored by the on-board computer (PCM). Each trouble code
has an assigned message that identifies the circuit, compo-
nent or system area where the problem was found.
OBD 2 diagnostic trouble codes are made up of five charac-
ters:
■ The 1st character is a letter. It identifies the “main system” where
the fault occurred (Body, Chassis, Powertrain, or Network).
■ The 2nd character is a numeric digit. It identifies the “type” of code
(Generic or Manufacturer-Specific).
Generic DTCs are codes that are used by all vehicle manu-
facturers. The standards for generic DTCs, as well as their
definitions, 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 stan-
dardized generic DTCs in order to comply with the new
OBD2 emissions standards. However, manufacturers are free
to expand beyond the standardized codes to make their sys-
tems easier to diagnose.
■ The 3rd character is a numeric digit. It identifies the specific sys-
tem or sub-system where the problem is located.
■ The 4th and 5th characters are numeric digits. They identify the
section of the system that is malfunctioning.
Diagnostic Trouble
Codes (DTCs) are
codes that identify a
specific problem area.