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Home >> Kia >> 2004 >> Optima L4-2.4L >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P0171 >> Enhanced Testing

Enhanced Testing



P0171 - System Too Lean

Description

Function

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%.

DTC Description

If long-term and short-term value are higher than the standard value, the PCM determines that a fault exists and a DTC is stored.





DTC Detecting Condition

Monitor DTC Status

Verify Presence of Related DTCs

1. Connect scantool to Data Link Connector.
2. Monitor the DTCs displayed on scantool.
3. Are DTCs present for any of the following items?

DTCs related to Mass airflow sensor(MAFS),Injector,Heated O2 sensor,Throttle position sensor(TPS), Engine coolant temperature sensor(ECT),Intake air temperature sensor(IAT), Manifold absolute pressure sensor(MAP),Purge control solenoid valve(PSCV)

YES
1) Perform all repairs associated with those codes before continuing.
NO
1) Go to "Inspection & Repair" procedure.

Terminal and Connector Inspection

1. Many malfunctions in the electrical system are caused by poor harness(s) and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.




2. Check the following conditions:

(1) Check for damaged harness and terminals: contact resistance, oxidation, bent or broken terminals.
(2) Check for poor connection between ECM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection
3. Has a problem been found?

YES
1) Repair as necessary and go to "Verification Vehicle Repair" procedure.
NO
1) Go to "System Inspection" procedure.

System Inspection

Check Intake System for Leak

1. Check the following items for leak:
- Throttle body gasket
- Gasket between intake manifold and surge tank
- Seals between intake manifold and fuel injectors
- Seals between surge tank and PCV valves
2. Does a leak exist?

YES
1) Repair as necessary, then go to "Verification of Vehicle Repair"
NO
1) Go to "Check for Exhaust Leak" procedure.


Check for Exhaust Leak

1. Check for leak in Exhaust.
2. Does a leak exist?

YES
1) Repair as necessary, then go to "Verification of Vehicle Repair"

NO
1) Go to "Check Fuel Line Pressure" procedure as below.


Check Fuel Line Pressure

1. Start the engine with the fuel pump disconnected to reduce the internal pressure of the fuel lines and hoses, and wait until the engine stalls before continuing.


NOTE: Be sure to reduce the fuel pressure before disconnecting the fuel main pipe and hose, otherwise fuel may spray out, possibly resulting in fire or injury.

2. Disconnect the battery negative(-) terminal and then connect the fuel pump harness connector.
3. Install the fuel pressure gauge using the appropriate adapter.
4. Connect the battery�s negative(-) terminal.
5. Check that there is no fuel leak from the pressure gauge or connections.
6. Disconnect the vacuum hose from the pressure regulator and plug the hose end.Measure the fuel pressure at idle.

A. [Specification] 320 ~ 350kPa (3.26~ 3.57kg/cm�, 46.4~50.7 psi)

7. Measure the fuel pressure when the vacuum hose is connected to the pressure regulator(while engine is running).

A. [Specification] 250 ~ 280kPa (2.55 ~ 2.86kg/cm�, 36.3~40.6 psi)

8. Is fuel pressure within specifications?

YES
1) Go to "Component Inspection" procedure

NO
1) If fuel pressure is below specifications, check for a malfunctioning fuel pump or pressure regulator. Check for a restricted fuel filter.
2) If fuel pressure is above specifications, check for a malfunctioning fuel pump or pressure regulator.
3) Go to "Verification of Vehicle Repair" procedure.

Component Inspection

Check Injectors for Restrictions or Fuel Leaks

1. Check for fuel leak between fuel delivery pipe and injectors.
2. Check injectors for restrictions.
3. Does a malfunction exist?

YES
1) Repair as necessary, then go to "Verification of Vehicle Repair" procedure.

NO
1) Possibility of malfunctioning PCM.Test with a new PCM and check for proper operation. If problem is corrected, replace with a new PCM and go to "Verification of Vehicle Repair" procedure.


Verification Vehicle Repair

After a repair, it may be necessary to check that fault is properly rectified.

1. Review and record the Freeze Frame Data for the Diagnostic Trouble Code (DTC) which has been diagnosed.
2. Using a Scantool, Clear DTC.


Caution:

Record all freeze frame data before disconnecting any connectors or clearing code(s). When DTCs are cleared, the Freeze Frame data which may help diagnosed an intermittent fault will also be erased from ECM's memory.

3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.


Caution:

Freeze Frame Data: The Freeze Frame function is designed to provide technicians with engine and vehicle information at the time a code is set. Freeze Frame can be thought of as a snapshot of certain operating conditions present at the time the MIL is turned on and a code set. Because this data is critical to determining the cause of a malfunction, this particular data is locked into a Freeze Frame Data memory location. If more than one DTC is encountered, the first one detected will have Freeze Frame Data available.

4. Perform Drive Cycle. Following Drive Cycle completion, access "Monitoring Test Results" from the Engine menu, then select "Readiness Test". Verify that all tests NOT displaying a "NOT APPLIC" status show a "COMPLETED" state. Once all tests have been verified as "COMPLETED", check for DTC�s. The presence of a "COMPLETED" status for all applicable tests, combined with the absence of any pending or confirmed DTCs, is an indicator that the fault is not present at that time.

5. Are any DTC�s present?
YES
1) Go to the applicable troubleshooting procedure.

NO
1) System performing to specification at this time.









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