Engine Control System (Diagnostics) (2.0L) - Introduction: General Description: Caution

Airbag system wiring harness is routed near the ECM, main relay and fuel pump relay.
CAUTION:
- Do not use electrical test equipment on the airbag system circuits.
- Be careful not to damage the airbag system wiring harness when servicing the ECM, TCM, main relay and fuel pump relay.
Never connect the battery in reverse polarity. Doing so will damage the ECM instantly, and other parts will also be damaged.
Do not disconnect the battery cables while the engine is running. A large counter electromotive force will be generated in the generator, and this voltage may damage electronic parts such as ECM etc.
When disconnecting the connectors of the electrical components, always be sure to turn the ignition switch to OFF. Perform the Clear Memory Mode after connecting the connectors. Refer to ENGINE (DIAGNOSTICS) (W/O STI)>CLEAR MEMORY MODE .
When measuring the voltage or resistance of individual sensor or all electrical control modules, use a tapered pin with a diameter of 0.6 mm (0.024 in) or less and touch it to the tip of terminal.

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Never insert the tapered pin into the terminal because it deforms inside which may lead to a malfunction.

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CAUTION: When replacing the ECM, be careful not to use the ECM of wrong specification to avoid any damage on the fuel injection system.

NOTE: When replacing the ECM of the models with immobilizer, immobilizer system must be registered. For detailed operation procedure, refer to the "REGISTRATION MANUAL FOR IMMOBILIZER".
The ECM connector is waterproof. When measuring the ECM connector terminal voltages, or the resistance between the ECM connector terminals, use the ST.

ST 18460AA030 CHECK BOARD
Take care not to allow water to get into the connectors when servicing or washing the vehicle in rainy weather. Avoid exposure to water even if the connectors are waterproof.
Use the ground terminal of the bulkhead harness for the grounding point when measuring voltage and resistance inside the passenger compartment.

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Use the engine ground terminal or engine assembly for the grounding point when measuring the voltage and resistance in engine compartment.

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All parts related to the engine control system are precision parts. Do not drop or otherwise apply impact. Do not reuse the parts that are dropped accidentally.
Do not connect the wiring of electrical parts directly to the battery terminals. It may cause erroneous operation of the charge control, leading to early deterioration of the battery or discharged battery.
Observe the following cautions when installing a radio in vehicle.
CAUTION:
- The antenna must be kept as far apart as possible from the ECM. Refer to ENGINE (DIAGNOSTICS) (W/O STI)>ELECTRICAL COMPONENT LOCATION>LOCATION>CONTROL MODULE .
- The antenna feeder must be placed as far apart as possible from the ECM and engine control system harness.
- Carefully adjust the antenna for correct matching.
- When mounting a large power type radio, pay special attention to the three items mentioned above.
- Incorrect installation of the radio may affect the operation of ECM.
When disconnecting the fuel hose, be sure to release the fuel pressure beforehand. Refer to FUEL INJECTION (FUEL SYSTEMS) (W/O STI)>FUEL>PROCEDURE>RELEASING OF FUEL PRESSURE .
Warning lights may illuminate when performing driving test with jacked-up or lifted-up condition, but this is not a system malfunction. The reason for this is the rotating speed difference between the front and rear wheels. When engine control system diagnosis is finished, perform the VDC memory clearance procedure of self-diagnosis function. Refer to VEHICLE DYNAMICS CONTROL (VDC) (DIAGNOSTICS)>CLEAR MEMORY MODE .