HOLDEN GEN III V8, Service Training

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GEN III V8 ENGINE MANAGEMENT
POWERTRAIN ON-BOARD DIAGNOSTIC SYSTEM CHECK
After the visual/physical underhood inspection, the On-Board Diagnostic System Check is the starting point for
all diagnostic procedures or finding the cause of an emissions failure
All Diagnostic procedures must always begin with the On-board Diagnostic System Check
Diagnostic procedures must begin with the On-Board Diagnostic System Check, which represents an organised
approach for identifying system problems
The ON-BOARD DIAGNOSTIC SYSTEM CHECK makes an initial check of the system, then will direct the
technician to other charts in the Service Manual It must be used as a starting point for all procedures The
entire diagnostic section in the VT Series Service Manual is set up in a specific order, that is, the ON-BOARD
DIAGNOSTIC SYSTEM CHECK will lead the technician to other charts, and those charts may lead to still other
charts THE SEQUENCE MUST BE FOLLOWED. The engine/transmission control system uses many input
signals and controls many output functions If the correct diagnostic sequence is not followed, incorrect
diagnosis and replacement of good parts may happen
Diagnostic charts incorporate diagnosis procedures using a Tech 2 where possible This Tech 2 is a small
hand-held computer in itself Its job is to give information to a technician about what is happening in the
engine/transmission management system
The Data Link Connector (DLC) is used by the assembly plant to perform end of line tests This connector can
also be used by technicians to monitor certain inputs and outputs as seen by the Powertrain Control Module
The Tech 2 reads and displays the information (serial data) supplied to the data link connector from the
Powertrain Control Module (PCM)
The correct procedure to diagnose a problem is to follow three basic steps
1 . Are the On-Board Diagnostics working? This is determined by performing the On-Board Diagnostic System
Check Since this is the starting point for the diagnostic procedures or finding the cause of a failure, always
begin here
If the On-Board Diagnostics are not working, the On-Board Diagnostic System Check will lead to a
diagnostic chart to correct the problem If the On-Board Diagnostics are working correctly, the next step is
2. Is there a Diagnostic Trouble Code stored
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If a diagnostic trouble code is stored, go directly to the
numbered diagnostic trouble code chart This will determine if the fault is still present If no diagnostic
trouble code is stored, then
3. Observe Serial Data transmitted by the PCM This involves reading the information available on the Serial
Data Stream with a Tech 2 Information on this tool and the meaning of the various displays can be found in
the succeeding paragraphs Typical data readings under a particular operating condition can be found on
the Tech 2 Data page
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