Decimal/Binary/Hexadecimal Conversions 6E1-33; Verifying Vehicle Repair; Reading Diagnostic Trouble Codes Using A Tech 2 Scan Tool - Isuzu 1999 RODEO Workshop Manual

f Fuel Trim
f Engine Speed
f Engine Load
f Engine Coolant Temperature
f Vehicle Speed
f TP Angle
f MAP/BARO
f Injector Base Pulse Width
f Loop Status
Intermittent Malfunction Indicator Lamp
In the case of an "intermittent" fault, the MIL ("Check
Engine" lamp) may illuminate and then (after three trips)
go OFF. However, the corresponding diagnostic trouble
code will be stored in the memory. When unexpected
diagnostic trouble codes appear, check for an intermittent
malfunction.
A diagnostic trouble code may reset. Consult the
"Diagnostic Aids" associated with the diagnostic trouble
code. A physical inspection of the applicable sub–system
most often will resolve the problem.
Data Link Connector (DLC)
The provision for communicating with the control module
is the Data Link Connector (DLC). It is located at the lower
left of the instrument panel. The DLC is used to connect to
the Tech 2 Scan tool. Some common uses of the Tech 2
are listed below:
f Identifying stored Diagnostic Trouble Codes (DTCs)
f Clearing DTCs
f Performing output control tests
f Reading serial data
Decimal/Binary/Hexadecimal Conversions
Beginning in 1996, Federal Regulations require that all
auto manufacturers selling vehicles in the United States
provide Scan tool manufacturers
information to display vehicle operating parameters. All
Scan tool manufacturers will display a variety of vehicle
RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
TS24064
with software
information which will aid in repairing the vehicle. Some
Scan Tools will display encoded messages which will aid
in determining the nature of the concern. The method of
encoding involves the use of a two additional numbering
systems: Binary and Hexadecimal.
The binary number system has a base of two numbers.
Each digit is either a 0 or a 1. A binary number is an eight
digit number and is read from right to left. Each digit has a
position number with the farthest right being the 0 position
and the farthest left being the 7 position. The 0 position,
when displayed by a 1, indicates 1 in decimal. Each
position to the left is double the previous position and
added to any other position values marked as a 1.
A hexadecimal system is composed of 16 different alpha
numeric characters. The alpha numeric characters used
are numbers 0 through 9 and letters A through F. The
hexadecimal system is the most natural and common
approach for Scan Tool manufacturers to display data
represented by binary numbers and digital code.

Verifying Vehicle Repair

Verification of vehicle repair will be more comprehensive
for vehicles with OBD II system diagnostics. Following a
repair, the technician should perform the following steps:
1. Review and record the Fail Records and/or Freeze
Frame data for the DTC which has been diagnosed
(Freeze Frame data will only be stored for an A or B
type diagnostic and only if the MIL has been
requested).
2. Clear DTC(s).
3. Operate the vehicle within conditions noted in the Fail
Records and/or Freeze Frame data.
4. Monitor the DTC status information for the DTC which
has been diagnosed until the diagnostic test
associated with that DTC runs.
Following these steps are very important in verifying
repairs on OBD II systems. Failure to follow these steps
could result in unnecessary repairs.
Reading Diagnostic Trouble Codes Using
A Tech 2 Scan Tool
The procedure for reading diagnostic trouble code(s) is to
use a diagnostic Scan tool. When reading DTC(s), follow
instructions supplied by tool manufacturer.
Clearing Diagnostic Trouble Codes
IMPORTANT: Do not clear DTCs unless directed to do
so by the service information provided for each diagnostic
procedure. When DTCs are cleared, the Freeze Frame
and Failure Record data which may help diagnose an
intermittent fault will also be erased from memory.
If the fault that caused the DTC to be stored into memory
has been corrected, the Diagnostic Executive will begin to
count the "warm–up" cycles with no further faults
detected, the DTC will automatically be cleared from the
PCM memory.
To clear Diagnostic Trouble Codes (DTCs), use the
diagnostic Scan tool "clear DTCs" or "clear information"
function. When clearing DTCs follow instructions
supplied by the tool manufacturer.
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