Equus 3120 - OBD 2&1 Tool Kit - Manual (Page 23)

OBD2 & 1 21
E
OBD2 Systems
DIAGNOSTIC TROUBLE CODES (DTCs)
On some Asian and European vehicles the DLC is located
behind the “ashtray” (the ashtray must be removed to access
it) or on the far left corner of the dash. If the DLC cannot be
located, consult the vehicle’s service manual for the location.
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.