| TIBURON(GK) >2003 > G 2.7 DOHC > Fuel System > General Information>Description and Operation |

MULTIPORT FUEL INJECTION (MFI)
GENERAL INFORMATION FUEL INJECTION CONTROL IDLE SPEED CONTROL IGNITION TIMING CONTROL OTHER CONTROL FUNCTIONS
1. | Fuel Pump Control : Turns the fuel pump relay ON so that current is supplied to the fuel pumpwhile the engine is cranking or running.
2. | A/C Compressor Clutch Relay Control : Turns the compressor clutch of the A/C ON and OFF.
3. | Fan Relay Control : The radiator fan and condenser fan speeds are controlled in response to theengine coolant temperature and vehicle speed.
4. | Evaporative Emission Purge Control (Refer to GROUP EC).
DIAGNOSTIC TEST MODE
• | When an abnormality is detected in one of the sensors or actuators relatedto emission control, the CHECK ENGINE/MALFUNCTION INDICATOR LAMP illuminatesas a warning to the driver.
• | When an abnormality is detected in one of the sensors or actuators, a diagnostictrouble code corresponding to the abnormality is output.
• | The RAM data inside the PCM that is related to the sensors and actuators canbe read by means of the scan tool. In addition, the actuators can be controlledunder certain circumstances.
HOW TO COPE WITH INTERMITTENT MALFUNCTIONS
1. | Ask the customer about the malfunction. Ask what it feels like, what it sounds like, etc. Then ask about driving conditions,weather, frequency of occurrence, and so on.
2. | Determine the conditions from the customer's responses. Typically, almost all intermittent malfunctions occur from conditions likevibration, temperature and/or moisture change, poor connections. From thecustomer's replies, it should be deduced which condition exists.
3. | Use the simulation test In the cases of vibration or poor connections, use the simulation tests belowto attempt to duplicate the customer's complaint. Determine the most likelycircuit(s) and perform the simulation tests on the connectors and parts ofthat circuit(s). Be sure to use the inspection procedures provided for diagnostictrouble codes and trouble symptoms. For temperature and/or moisture conditionsrelated intermittent malfunctions, using common sense, try to change the conditionsof the suspected circuit components, then use the simulation tests below.
4. | Verify that the intermittent malfunction is eliminated. Repair the malfunctioning part and try to duplicate the condition(s) againto verify that the intermittent malfunction has been eliminated.
• | Shake the connector up-and-down, right-and-left.
• | Shake the wiring harness up-and-down, right-and-left.
• | Vibrate the part or sensor.
SERVICE POINTS IN INSPECTING A BLOWN FUSE
• | Harness being crushed by the vehicle body.
• | Damage to the outer casing of the harness due to wear or heat.
• | Water getting into the connector or circuitry.
• | Human error (mistakenly shorting a circuit, etc.).
INSPECTING THE MFI SYSTEM
1. | Engine is hard to start or does not start at all
2. | Unstable idle
3. | Poor driveability
ON-BOARD DIAGNOSTICS
• | Diagnostic trouble codes are set as follows: After the PCM first detects a malfunction, a diagnostic trouble code is recorded when the engine is restarted and the same malfunction is re-detected. (Themalfunction is detected in driving cycle). However, for fuel system rich/lean misfiring, a diagnostic trouble code is recorded on the first detection of the malfunction.
• | Erasing diagnostic trouble codes: After recording the diagnostic trouble code, if the PCM does not re-detect the malfunction for 40 driving cycles, the diagnostic trouble code will be erased from the PCM memory. However, for fuel system rich/lean or misfiring,the diagnostic trouble code will be erased if both of the following conditions are met:
- | When driving conditions (engine speed, engine coolant temperature, etc.) are identical to those when the malfunction was first recorded.
- | When the PCM does not re-detect the malfunction for 80 driving cycles.
A "driving cycle" is complete as soon as the vehicle goes into closed-loop operation.
• | Catalyst
• | Fuel system
• | Air flow sensor (MAF sensor)
• | Intake Air Temperature Sensor (IAT sensor)
• | Engine Coolant Temperature Sensor (ECT sensor)
• | Throttle Position Sensor (TPS)
• | Front Oxygen Sensor
• | Rear Oxygen Sensor Heater
• | Rear Oxygen Sensor
• | Front Oxygen Sensor Heater
• | Injector
• | Misfire
• | Crankshaft Position Sensor (CKP sensor)
• | Camshaft Position Sensor (CMP sensor)
• | Evaporative Emission Control System
• | Vehicle Speed Sensor (VSS)
• | Idle Speed Control
• | PCM
1. | After turning the ignition key on, check that the light illuminates for 5 seconds without the engine running.
2. | If the light does not illuminate, check for an open circuit in the harness,blown fuse and blown bulb.
• | When battery voltage is excessively low, diagnostic trouble codes can not be read. Be sure to check the battery for voltage and the charging system before starting the test.
• | Codes are erased if the battery or the PCM connector is disconnected. Do not disconnect the battery before the diagnostic trouble codes are completely read and recorded.
1. | Turn OFF the ignition switch.
2. | Connect the scan tool to the data link connector on the lower crash pad.
3. | Turn ON the ignition switch.
4. | Use the Hi-Scan Pro to check the diagnostic trouble code.
5. | Repair the faulty part from the diagnosis chart.
6. | Erase the diagnostic trouble code.
7. | Disconnect the Hi-Scan Pro.
TROUBLESHOOTING DIAGNOSTIC TROUBLESHOOTING FLOW