Clarke 4501135, User Instructions

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6. Use extreme caution when working around the ignition coil,
distributor cap, ignition wires and spark plugs. These components
create hazardous voltages when the engine is running.
7. Always put the transmission in PARK (for automatic transmission)
or NEUTRAL (for manual transmission) and make sure the parking
brake is engaged.
8. Keep a fire extinguisher suitable for fuel / chemical /electrical fires
nearby.
9. Do
n’t connect or disconnect any test equipment with the ignition on,
or engine running.
10. Keep the code reader dry, clean and free from oil, water and
grease. Use a mild detergent on a clean cloth to clean the
outside of the device when necessary.
2. GENERAL INFORMATION
2.1 On-Board-Diagnostics (OBD) 2
The first generation of On-Board Diagnostic (called OBD I), was
developed by the California Air Resources Board (ARB) and
implemented in 1988 to monitor some of the emission control
components on vehicles. As technology and the desire to improve
On-Board Diagnostic capability increased, a new generation of On-
Board Diagnostics system was developed. This second generation of
On-Board Diagnostic regulations is called "OBD II".
The OBD II system is designed to monitor emission control systems
and key engine components by performing either continuous or periodic
tests of specific components and vehicle conditions. When a problem is
detected, the OBD II system turns on a warning lamp (MIL) on the
vehicle instrument panel to alert the driver typically by the phrase of
“Check Engine” or “Service Engine Soon”. The system will also store
important information about the detected malfunction so that a
technician can accurately find and fix the problem.
Here below follow three pieces of such crucial information:
● Whether the Malfunction Indicator Light (MIL) is commanded
'on' or 'off';
● Which if any, Diagnostic Trouble Codes (DTCs) are stored;
● Readiness Monitor status
2.2 Diagnostic Trouble Codes (DTCs)
OBD II Diagnostic Trouble Codes are codes that are stored by the
on-board computer diagnostic system in response to a problem found in
the vehicle. These codes identify a particular problem area and are