Engine Controls - Engine (Diagnostics) (H6DO): General Description: Caution
- Airbag system wiring harness is routed near the ECM, main relay and fuel pump relay.CAUTION:
- All airbag system wiring harnesses and connectors are yellow. Do not use the electrical test equipment on these 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.
- The ECM will be destroyed instantly.
- The fuel injector and other parts will be damaged.
- Do not disconnect the battery terminals 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.
- Before disconnecting the connectors of each sensor and ECM, be sure to turn the ignition switch to OFF. Perform the Clear Memory Mode after connecting the connectors.
- Poor contact has been identified as a primary cause of this problem. Measure the voltage or resistance of individual sensor or all electrical control modules using 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.
- Remove the ECM from the located position after disconnecting two cables on battery. Otherwise, the ECM may be damaged.CAUTION: When replacing the ECM, be careful not to use the wrong spec. ECM to avoid any damage on the fuel injection system.
- Connectors of each sensor in the engine compartment and the harness connectors on the engine side and body side are all designed to be waterproof. Even if the connectors are waterproof, take care not to allow water to get into them when washing the vehicle, or when servicing the vehicle in rainy weather.
- Use ECM mounting stud bolts as the grounding point to chassis when measuring voltage and resistance in the passenger compartment.
- Use the engine ground terminal or engine assembly as the grounding point to chassis when measuring the voltage and resistance in engine compartment.
- Use TCM mounting stud bolts at the body side grounding point when measuring voltage and resistance inside the passenger compartment.
- Every MFI-related part is a precision part. Do not drop them.
- Observe the following cautions when installing a radio in MFI equipped models.CAUTION:
- The antenna must be kept as far apart as possible from control unit. (The ECM is located under the steering column, inside of instrument panel lower trim panel.)
- 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 mentioned above.
- Incorrect installation of the radio may affect the operation of ECM.
- 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.
- Problems in the electronic-controlled automatic transmission may be caused by failure of the engine, the electronic control system, the transmission proper, or by a combination of these. These three causes (engine, electrical control system, transmission) must be distinguished clearly when performing diagnostics.
- Diagnostics should be conducted by rotating with simple, easy operations and proceeding to complicated, difficult operations, of a fault or trouble. The most important thing in diagnostics is to understand the customer's complaint, and distinguish between the three causes (engine, electrical control system, transmission).
- In AT models, do not continue the stall for more than five seconds at a time, (from closed throttle, fully open throttle to stall speed reading, and then decrease engine speed.)
- For the model with ABS, the ABS warning light 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 speed difference between the front and rear wheels. After diagnosis of engine control system, perform the ABS memory clear procedure of self-diagnosis function.