3.
Monitor sensors related to fuel trim(Ex. HO2S,MAFS,MAPS,TPS,MAPS,TPS,ECTS,PCSV,Injectors etc.) with scantool
ideal air-fuel ratioto so as to raise the efficiency of catalytic convertor. Generally, NOx increases at lean combustion while CO, HC increases in rich combustion. Thus, in order to purge all of these gases with catalytic convertor, air-fuel ratio should be nearly at the ideal ratio. However the range in which all gases purified successfully is too narrow, it is impossible to meet ideal range with open loop control, therefore feed back control using HO2S is required. HO2S output signal changes rapidly near ideal air-fuel ratio and this characteristic is used at feed back control. comparing HO2S output signal and reference value, PCM increases fuel injection quantity at lean condition and decreases at rich condition. As deterioration of engine, due to the characteristic changes of many components of intake and fuel line or inevitable tolerance of components at production process, achieving ideal air-fuel ratio is almost impossible with the fixed fuel injectionduration. Regarding the change of cross section by clogged injector, feed back correction is performed yet, it cannot cover all the ranges. It means if the correction range is massively seperated from the ideal value or if the mean of feed back control range too inclines to lean or rich condition, feed back correction does not work efficiently. Therefore processing correction value throughout long time statistically during driving, PCM controlls fuel injection duration as fitting the mean to be the ideal air-fuel ratio value. Through adaptive control, accuracy of the control could be improved and the value of adaptive control varies countiuously during driving and is always up-dated.
Checking air-fuel ratio correction value every 0.75 sec. at idle, if the value within the detecting condition for more than 0.3 sec., PCM sets P2187. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Fuel Trim Idle Condition Option Limits Exceeded | ● Sensors related to Fuel Trim ● Intake system ● Fuel Pressure ● Faulty PCM |
EnableConditions | ● 550rpm ≤ Engine Speed ≤ 4000rpm ● 60℃ (140℉) ≤ Engine coolant temperature ≤ 114.992℃ (239℉) ● -10℃ (14℉) ≤ Intake Air Temperature ≤ 60℃ (140℉) ● 0° ≤ Throttle Position ≤ 72° ● 25kPa ≤ Engine Load ≤ 90kPa ● 1.5g/s ≤ Intake Air Flow ≤ 80g/s ● Barometric Pressure ≥ 72kPa ● Vehicle Speed ≤ 130km/h ● System Voltage ≥ 11V ● Closed Loop Active ● Other diagnostic fault not active | |
Threshold value | ● Average of short term fuel trim 〉1.5 ● Average of long term fuel trim 〉0.76 | |
DiagnosisTime | ● Contineous (More than 0.375sec. Failure for every 0.75sec. Test) | |
MIL On Condition | ● 2 Driving Cycles |
Connect scantool to DLC(Data Link Connector)
Warm up the engine to normal operating temperature.
Monitor sensors related to fuel trim(Ex. HO2S,MAFS,MAPS,TPS,MAPS,TPS,ECTS,PCSV,Injectors etc.) with scantool
Are those parameters displayed correctly ?
▶Fault is intermittent caused by poor contact in Sensor’s and/or PCM’s connector or was repairedand PCM memory was not cleared. Thoroughly check connectors for looseness, poorconnection, bending, corrosion, contamination, deterioration, or damage. Repair or replaceas necessary and go to "Verification of Vehicle Repair" procedure
▶Go to "Terminal and connector inspection" procedure.
Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to "System Inspection " procedure.
Check Air leakage
Check gasket is contaminated or misinstalled.
▶ Installation or any damage of Throttle body gasket
▶ Installation or any damage of the gasket between intake manifold and surge tank.
▶ Clogging of intake manifold or injectors resulting from foreign materials.
▶ Open stuck of PCSV caused by foreign materials between surge tank and PCSV.
Has a problem been found ?
▶ Repair or replace as necessary and then, go to "Verification of Vehicle Repair" procedure.
▶ Go to "Check Fuel Line Inspection" as follows.
Check Fuel Line Inspection
Check clog, contamination and installation of each hose as follows.
▶ Check connection of each fuel line.
▶ Check damage, interference and installation of vaccum hose connected to fuel line.
▶ Check that fuel pipe in the fuel line is bent and sqeezed.
▶ Check any fuel leakage from fuel pipe in the fuel line.
Has a problem been found ?
▶ Repair or replace as necessary and then, go to "Verification of Vehicle Repair" procedure.
▶ Go to "Check fuel pressure" as follows.
Check Fuel Pressure
Refer to "Fuel pressure test" in "Fuel delivery system"
Is the measured fuel pressure within specification ?
▶ Go to "Component Inspection" procedure.
▶ Repair or replace as necessary and the, go to "Verification of Vehicle Repair" procedure.
Check PCV
IG "OFF".
Remove PCV valve and then, check that plunger in the PCV is moving.
Is the PCV normal ?
▶ Go to "Check PCSV" as follows.
▶ Substitute with a known-good PCV and check for proper operation. If the problem is corrected,replace PCV and then go to "Verification of Vehicle Repair" procedure.
Check PCSV
IG "OFF".
Remove PCSV and Vaccum Hose
Check that PCSV is just one way solenoid valve
Is the PCSV normal ?
▶ Go to "Check injector" as follows.
▶ Substitute with a known-good PCSV and check for proper operation. If the problem is corrected,replace PCSV and then go to "Verification of Vehicle Repair" procedure.
Check injector
IG "OFF"
Remove injector.
Check that injector hole is clogged by foreign materials.
Measure resistance between terminal 1 an 2 of injector connector.(Component Side)
Temp. | Resistance |
20℃ (68℉) | 11.4 ~ 12.6Ω |
Is the measured resistance within specification ?
▶ Go to "Check component related to fuel trim" as follows.
▶ Substitute with a known-good injector and check for proper operation. If the problem is corrected,replace injector and then go to "Verification of Vehicle Repair" procedure.
Check component related to fuel trim
Check component related to fuel trim such as HO2S, MAFS,MAPS, TPS, ECTS, PCSV and Injectores) - Refer to each designated trouble shooting guide.
Are those component related to fuel trim O.K ?
▶ Substitute with a known-good PCM and check for proper operation. If the problem is corrected,replace PCM and then go to "Verification of Vehicle Repair" procedure.
There is a memory reset function on scantool that can erase optional parts automaticallydetected and memorized by PCM.
▶ Repair or replace as necessary and then, go to "Verification of Vehicle Repair" procedure.
After a repair, it is essential to verify that the fault has been corrected.
Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
Using a Scantool, Clear the DTCs
Operate the vehicle within conditions noted in the freeze frame data or enable conditions
Monitor that all rediness test have been verified as " Complete "
Are any DTCs present ?
▶ Go to the applicable troubleshoooting procedure.
▶ System is performing to specification at this time.
