B - MFI Control System
[B] MFI CONTROL SYSTEM1. LINEAR OXYGEN SENSOR
^ Output Signal of Linear 02 sensor (NTK TL-6314)
Description:
The typical Oxygen Sensor (Zirconia 02 Sensor)
^ (as used in most Hyundai vehicles, including the non-SULEV Elantra)
^ Works essentially as a "switch."
^ It can determine if the mixture is rich or lean by detecting the Oxygen concentration. But, it doesn't indicate how rich or lean the mixture is.
^ The rich condition is indicated by a high output voltage (near 1 Volt).
^ The lean condition is indicated by a low output voltage (near 0 Volt).
The Linear Oxygen Sensor
^ Has the ability to not only indicate if the mixture is rich or lean but also how rich or lean the mixture is.
^ This ability is important in more closely controlling the Air/Fuel ratio in order to reduce exhaust emissions or when the engine is desired to be operated in a lean condition, for example.
^ The graph previously shown illustrates the difference in the signal outputs. The output signal of the Linear Oxygen Sensor is a variable CURRENT (positive and negative) whereas the output of the typical Zirconium Oxygen Sensor is a variable VOLTAGE.
Things to Note About the Linear Oxygen Sensor:
^ Although the Linear 02 Sensor's signal to the ECM is a variable current, this information is NOT available for diagnostic purposes.
^ The ECM processes the current information and outputs a variable voltage signal which CAN be used for diagnostic purposes.
^ The signal voltage range is 0 to 5 Volts.
^ In the case of the Linear 02 Sensor used on the XD SULEV, a stoichiometric mixture equates to about 2.0 Volts.
^ A LEAN mixture is indicated by a HIGH voltage (like the Titanium Sensor).
^ A RICH mixture is indicated by a LOW voltage (like the Titanium Sensor).
^ NOTE:
Keep in mind that the Rear 02 sensor on the XD SULEV is a typical Zirconium 02 Sensor (Rich ~ 1 Volt, Lean ~ 0 Volt), with opposite indication of rich and lean versus the Linear Front 02 Sensor.
^ The Linear 02 Sensor has 6 pins.
^ The 02 sensor connector housing has some numbers molded-in, indicating pin numbers. This information is not applicable to the XD SULEV. The Hyundai numbering system is different from what's molded into the sensor connector.
^ *The pictures show the correct Hyundai numbering system, the numbers on the previous TSB where incorrect .*
Typical Linear 02 Sensor Signal Recording as shown (Using Hi-Scan Pro Flight Recording).
Circuit Diagram
*Linear 02 Sensor Heater Inspection Procedures. The checking of the ground to the PCM diagram is incorrect in the previous TSB. The check should be between pins 1 at the O2 connector to pin 8 at the ECM connector. The last check for O2 heater resistance is incorrect, this TSB shows the correct information.*
CAUTION:
Do not check the sensors internal circuits with tester except for the internal resistance.
Step 2 of the harness inspection procedure
The table shows the pin relationship between the 02 Harness Connector and the PCM.
WARNING:
When checking for opens or short-to-grounds, use a small pin to gently contact the female pins on the PCM connector and the 02 connector. Touch the pins only. DO NOT attempt to insert the pin. The very small female pins can be easily damaged. If damaged, the control harness will require replacement to repair.
Hint:
When checking for a short to ground or circuit continuity, using the "AUDIBLE ALERT" feature of the DVOM allows for testing without having to look at the DVOM display. When the probes are manipulated to touch the correct pin to check for a short to ground or continuity, the audible alert will allow the tester to know as soon as the pin is contacted whether there is or is not a problem.
Step 3 of the harness inspection procedure -- Checking the Sensor Heater's Internal Resistance:
WARNING:
Be sure to take the resistance of the DVOM probe wiring you are using into account. When measuring small resistance values, the built-in resistance of the probes and any wiring, clips, extensions, etc. will have an affect on the reading.
EXAMPLE:
^ In the case of the Linear 02 Sensor, the standard internal heater resistance specification is very small (2.42 ~ 2.92 ohms at room temperature: 68°F = 20°C).
^ When the resistance was measured using a DVOM, the resistance value was found to be 3.3 ohms. This value is Out-of-Spec. and would imply the need to replace the Linear 02 Sensor.
^ The above measurement was made without taking into account the internal resistance of the wiring, clips and extensions used to make the measurement.
^ To take into account this resistance, calibrate the DVOM by using the "ZERO" feature of the DVOM.
^ First, attach all the probes, wires and clips that will be used to connect to the 02 sensor pins to the DVOM.
^ Connect the positive and negative leads together.
^ The DVOM will indicate the internal resistance of the wiring and clips. In this example, the value is 0.5 ohms. Use the "ZERO" feature of the DVOM to calibrate the resistance value to zero.
^ After using the "ZERO" feature, the display will indicate 0.0 ohms.
^ *Now, connect the leads to the 02 Sensor (pins # 5 and 6) and measure the resistance. The pin numbering and diagram has been corrected in this TSB*.
^ The result of the resistance measurement AFTER zeroing is 2.8 Ohms. This value is within the specifications for the sensor (2.42 ~ 2.92 Ohms).
2. INJECTOR
INSTALLATION OF INJECTORS AND DELIVERY PIPES
1. Install the new grommet to each injector. (Refer to Grommet and O-ring of injector in this TSB for details)
2. Apply a light coat of oil to the new 0-ring and install them to each injector.
3. Apply a light coat of oil where the fuel delivery pipe touches the 0-ring.
4. While rotating the injector, push it into the deliver pipe. Position the injector connector outward.
5. Apply a light coat of oil where the intake manifold touches the 0-ring of the injector.
6. Place the delivery pipe with all 4 injectors in position on the intake manifold.
7. Temporarily install the 2 bolts holding the delivery pipe to the intake manifold.
8. Check that the injectors rotate smoothly.
NOTE:
If the injectors do not rotate smoothly, the probable cause is incorrect installation of 0-ring.
9. Tighten the 2 bolts holding the delivery pipe to the cylinder head.
3. MAF & IAT SENSOR
Description:
A Mass Air Flow (MAF) sensor is used on the SULEV engine versus the Manifold Absolute Pressure (MAP) sensor used on the non-SULEV engine. This change allows more accurate mass air flow information to the ECM for precise engine control.
The Intake Air Temperature (IAT) sensor is built into the MAF sensor assembly.
Circuit diagram
The MAF Sensor and connector are unique to the XD Elantra SULEV Engine.
Spark Plug Information:
The SULEV Engine uses Iridium Spark Plugs (made by NGK).
These plugs have the following positive characteristics:
^ More stable ignition during cold starts with a leaner air/fuel mixture (better for emissions)
^ Longer Durability
The part numbers in the picture above are for NGK brand spark plugs.
Harness Inspection Procedures:
WARNING:
When checking for opens or short-to-grounds, use a small pin to gently contact the female pins on the PCM connector and the MAF connector. Touch the pins only. DO NOT attempt to insert the pin. The very small female pins can be easily damaged. If damaged, the control harness will require replacement to repair.
Refer to Diagnostic Trouble Code List shown in this TSB for additional hints.
Troubleshooting Procedures