Page 344 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

7 To prevent damage to the on-board computer
when taking vehicle electrical measurements,
always use a digital multimeter with at least 10
megOhms of impedance.

8 Fuel and battery vapors are highly flammable.
To prevent an explosion, keep all sparks, heated
items and open flames away from the battery and
fuel / fuel vapors. DO NOT SMOKE NEAR THE
VEHICLE DURING TESTING.

9 Don’t wear loose clothing or jewelry when working on an engine. Loose clothing can become caught in the
fan, pulleys, belts, etc. Jewelry is highly conductive, and can cause a severe burn if it makes contact between
a power source and ground.
10 Be extra cautious when working around the ignition coil, distributor cap, ignition wires and spark plugs. These
components produce hazardous voltages when the engine is running.
11 Put blocks in front of the drive wheels and never leave the vehicle unattended while running tests.

12 Put the transmission in PARK (for automatic transmission) or NEUTRAL (for manual transmission) and make
sure the parking brake is engaged.
13 Keep a fire extinguisher suitable for gasoline/chemical/ electrical fires nearby.

14 Don’t connect or disconnect any test equipment while the ignition is on or the engine is running.
15 Keep the scan tool dry, clean, free from oil/water or grease. Use a mild detergent on a clean cloth to clean the
outside of the scan tool, when necessary.

16 Put blocks in front of the drive wheels and never leave the vehicle unattended while running tests.
17 Keep clothing, hair, hands, tools, test equipment, etc. away from all moving or hot engine parts.
18 Keep clothing, hair, hands, tools, test equipment, etc. away from all moving or hot engine parts.
Diagnostic Trouble Codes (DTCs)
OBD II Diagnostic Trouble Codes are codes that 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 intended to provide you
with a guide as to where a fault might be occurring within a vehicle. OBD II Diagnostic Trouble Codes consists
of a five-digit alphanumeric code. The first character, a letter, identifies which control system sets the code. The
other four characters, all numbers, provide additional information on where the DTC originated and the operating
conditions that caused it to set. Here below is an example to illustrate the structure of the digits:
Diagnostic Trouble Codes (DTCs) are meant to guide you to the proper service procedure in the vehicle’s service
manual. DO NOT replace parts based only on DTCs without first consulting the vehicle’s service manual for
proper 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
monitored by the on-board computer (PCM). Each trouble code has an assigned message that identifies the
circuit, component or system area where the problem was found.

331
CITS : Automotive - Mechanic Diesel - Lesson 104 - 107 CITS : Automotive - Mechanic Diesel - Lesson 104 - 107