GENERAL DESCRIPTION
Engine (Diagnostics)
3. General Description
S068001
8) Use engine grounding terminal   or engine
proper as the grounding point to the  body when
measuring voltage and resistance in  the engine compartment.
A: CAUTION
S068001A03
1)  Airbag system wiring harness is routed near the engine control module (ECM), main relay and fuel pump relay.
CAUTION:
•  All Airbag system wiring harness and con­nectors are colored yellow. Do not use electri­cal test equipment on these circuit.
•  Be careful not to damage Airbag system wir­ing harness when servicing the engine control module (ECM), transmission control module (TCM), main relay and fuel pump relay.
2)   Never connect the battery in reverse polarity.
•  The ECM will be destroyed instantly.
•  The fuel injector and other part will be damaged in just a few minutes more.
3)   Do not disconnect the battery terminals while the engine is running.
•  A large counter electromotive force will be gen­erated in the alternator, and this voltage may dam­age electronic parts such as ECM, etc.
4)   Before disconnecting the connectors of each sensor and the ECM, be sure to turn OFF the igni­tion switch.
5)   Poor contact has been identified as a primary cause of this problem. To measure the voltage and/or resistance of individual sensors or all elec­trical control modules at the harness side connector, use a tapered pin with a diameter of less than 0.64 mm (0.025 in). Do not insert the pin more than 5 mm (0.20 in) into the part.
6)   Before removing ECM from the located position, disconnect two cables on battery.
•  Otherwise, the ECM may be damaged.
CAUTION:
When replacing ECM, be careful not to use the wrong spec. ECM to avoid any damage on fuel injection system.
7)  The connectors to each sensor in the engine compartment and the harness connectors on the engine side and body side are all designed to be waterproof. However, it is still necessary to take care not to allow water to get into the connectors when washing the vehicle, or when servicing the vehicle on a rainy day.
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9) Use TCM mounting stud bolts at the body head grounding point when measuring voltage and resistance inside the passenger compartment.
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10)   Every MFI-related part is a precision part. Do not drop them.
11)  Observe the following cautions when installing a radio in MFI equipped models.
CAUTION:
•  The antenna must be kept as far apart as possible from the control unit.
(The ECM is located in the engine compart­ment.)
•  The antenna feeder must be placed as far apart as possible from the ECM and MFI har­ness.
•  Carefully adjust the antenna for correct matching.
•  When mounting a large power type radio, pay special attention to the three items above mentioned.
•  Incorrect installation of the radio may affect the operation of the ECM.
12)   Before disconnecting the fuel hose, discon­nect the fuel pump connector and crank the engine for more than five seconds to release pressure in the fuel system. If engine starts during this operation, run it until it stops.
13)   Problems in the electronic-controlled auto­matic transmission may be caused by failure of the
EN(SOHCw/oOBD)-6
GENERAL DESCRIPTION
Engine (Diagnostics)
engine, the electronic control system, the transmis­sion proper, or by a combination of these. These three causes must be distinguished clearly when performing diagnostics.
14)   Diagnostics should be conducted by rotating with simple, easy operations and proceeding to complicated, difficult operations. The most impor­tant thing in diagnostics is to understand the cus­tomer's complaint, and distinguish between the three causes.
15)   In AT vehicles, do not continue the stall for more than five seconds at a time (from closed throttle, fully open throttle to stall engine speed).
16)  On ABS vehicle, when performing driving test in jacked-up or lifted-up position, sometimes the warning light may be lit, but this is not a malfunc­tion of the system. The reason for this is the speed difference between the front and rear wheels. After diagnosis of engine control system, perform the ABS memory clearance procedure of self-diagno­sis system.
2. ENGINE GROUNDING
S068001A1002
Make sure the engine grounding terminal is prop­erly connected to the engine.
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C: NOTE
S068001A15
1. ENGINE AND EMISSION CONTROL
SYSTEM
S068001A1501
•  The Multipoint Fuel Injection (MFI) system is a system that supplies the optimum air-fuel mixture to the engine for all the various operating condi­tions through the use of the latest electronic tech­nology.
With this system fuel, which is pressurized at a constant pressure, is injected into the intake air passage of the cylinder head. The injection quan­tity of fuel is controlled by an intermittent injection system where the electro-magnetic injection valve (fuel injector) opens only for a short period of time, depending on the quantity of air required for one cycle of operation. In actual operation, the injection quantity is determined by the duration of an elec­tric pulse applied to the fuel injector and this per­mits simple, yet highly precise metering of the fuel.
•   Further, all the operating conditions of the engine are converted into electric signals, and this results in additional features of the system, such as large improved adaptability, easier addition of com­pensating element, etc.
The MFI system also has the following features:
•   Reduced emission of harmful exhaust gases.
•   Reduced in fuel consumption.
•   Increased engine output.
•  Superior acceleration and deceleration.
•  Superior startability and warm-up perfor­mance in cold weather since compensation is made for coolant and intake air temperature.
B: INSPECTION
S068001A10
Before performing diagnostics, check the following items which might affect engine problems:
1. BATTERY S068001A1001
1)   Measure battery voltage and specific gravity of electrolyte.
Standard voltage: 12 V Specific gravity: Above 1.260
2)  Check the condition of the main and other fuses, and harnesses and connectors. Also check for proper grounding.
EN(SOHCw/oOBD)-7
GENERAL DESCRIPTION
Engine (Diagnostics)
D: PREPARATION TOOL
S068001A17
ILLUSTRATION
TOOL NUMBER
DESCRIPTION
REMARKS
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24082AA150 (Newly adopted tool)
CARTRIDGE
Troubleshooting for electrical systems.
B2M3876
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22771AA030
SELECT MONITOR KIT
Troubleshooting for electrical systems.
•  English: 22771AA030 (Without printer)
•  German: 22771AA070 (Without printer)
•  French: 22771AA080 (Without printer)
•  Spanish: 22771AA090 (Without printer)
B2M3877
EN(SOHCw/oOBD)-8
GENERAL DESCRIPTION
Engine (Diagnostics)
MEMO:
EN(SOHCw/oOBD)-9