GENERAL DESCRIPTION |
In order to provide the best possible combination of drivability, fuel economy and emission control, the PCM uses a closed loop air/fuel metering system. The PCM monitors the HO2S signal voltage and adjusts fuel delivery based it in closed loop fuel control. Changes in fuel delivery will be indicated by the long-term and the short-term fuel trim values. The ideal fuel trim value is around 0%. The PCM will add fuel when the HO2S signal is indicating a lean condition. Additional fuel is indicated by fuel trim values that are above 0%. The PCM will reduce fuel when the HO2S signal is indicating a rich condition. Reduction in fuel is indicated by fuel trim values that are below 0%. The DTC relevant to fuel trim will be set when the amount reaches excessive levels because of a lean or rich condition.
DTC DESCRIPTION |
Checking the fuel trime value under detecting condition, if its average exceeds the limit over certain period, PCM sets P0174.
DTC DETECTING CONDITION |
Item | Detecting Condition | Possible Cause | ||||||||||
DTC Strategy |
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Enable Conditions |
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Threshold value |
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Diagnosis Time |
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MIL On Condition |
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MONITOR GDS DATA |
1. | Monitor DTCs related to MAFS, MAPS, ECTS, Injector or CVVT items with scantool. |
2. | Are there the DTCs above-mentioned?
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SYSTEM INSPECTION |
■ Check air leakage |
1. | Visually/physically inspect the air leakage in intake/exhaust system for following items. ▶ Vacuum hoses for splits, kinks and improper connections. ▶ Throttle body gasket ▶ Gasket between intake manifold and cylinder head ▶ Seals between intake manifold and fuel injectors ▶ Exhaust system between HO2S and three way catalyst for air leakage |
2. | Has a problem found in this procedure?
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■ Check the fuel line |
1. | Check the fuel line for following items ▶ Connector connection state ▶ Damage/ connection state for vacuum hoses connected to fuel line ▶ Bent/ pressed/ twisted fuel line or fuel leakage |
2. | Has a problem found in this procedure?
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■ Check fuel pressure |
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1. | IG “OFF” and disconnect Fuel Pump Relay in Junction Box. |
2. | Start-up and wait until it stops itself. |
3. | IG “OFF” and connect Fuel Pump Relay. |
4. | Install the fuel pressure gauge to the delivery pipe with the fuel pressure gauge adaptor. |
5. | Activate the fuel pump, and with fuel pressure applied, check that there is no fuel leakage from the pressure gauge or connection part. |
6. | Measure the fuel pressure at idle.
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7. | Is the measured fuel pressure within specifications ?
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COMPONENT INSPECTION |
■ Check PCV |
1. | IG “OFF” and remove PCV valve from rocker cover. |
2. | Insert a thin stick into the PCV valve from the threaded side and verify that the plunger is moving. |
3. | Is the PCV valve normally moving?
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■ Check injector for normal operation |
1. | Start engine. |
2. | Check its RPM decrease when doing the injector’s actuation test. |
3. | Is there any cylinder with no change in RPM or only a small change in RPM?
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