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ENGINE APPLICATION MANUAL GM Powertrain
Gasoline 4.3L V6 90 Degree Revised: 08/15/2000
File: c:\data\manuales\v6-truck\am43v6#3.doc
Contact:Luis Nespolo - (248) 857-1558 Printed: 8/15/00
64
4.1.3.1 Onboard Diagnostics
Onboard diagnostic refers to the ability of the Powertrain control system to self diagnose
emission performance related problems and communicate the existence of such problems to
the vehicle operator via the “Service Engine Soon” telltale light present in the vehicle
instrument panel, or to the service technician via a serial data communication tool attached
to what has been the Assembly Line Data Link (ALDL), but what is becoming an industry
standard “Class 2” serial data link per SAE J1850.
a. Improve in-use compliance with emission standards for the lifetime of the vehicle.
b. Detect & identify deterioration and malfunction of emission related components and
systems.
c. Augment/supplant current inspection/maintenance programs.
d. Detect deterioration or malfunction of individual emission related components.
e. Define a standardized electronic communication protocol to enable interrogation of the
control system so as to allow independent service stations the ability to diagnose and repair
emission related failures with communized electronic instruments across various
manufacturer’s product lines.
4.1.3.2 Applicability
Table 4.1.3.2 -1 defines the applicability of Federal OBD II requirements to Federally
emission certified full size GMTG vehicles.
GVWR (Lbs.) OBDII Compliance Requirements
EPA California
< 8500 Lbs. yes yes
8500 < GVWR < 14000 no N/a
> 14000 Lbs. N/a N/a
Table 4.1.3.2-I. Applicability of Federal/California OBD II Full-Size Vehicles
4.1.3.3 Requirements
Federal OBD II requirements may be categorized into two basic groups. The two groups
include:
a. Standardization requirements
b. Diagnostic Requirements specific to Federal OBD II
Requirement Description
Data Link Connector and Protocol SAEJ1850 - Specifics requirements for vehicle data
communications network. GM implementation of this
standard known as Class 2 Serial Data
SAEJ1962 - Specifies the new 16 pin under dash
diagnostic connector.
SAEJ1978 - Specifies the OBD II scan tool which is
designed to attach and communicate via the under
dash diagnostic connector.
Test Modes and Fault Codes SAEJ1979 - Specifies CARB/EPA functions and
messages
Parameter Information SAEJ2012 - Specifies format and messages for
diagnostic trouble codes