P0172
DTC P0172 SYSTEM TOO RICH (BANK 1)GENERAL DESCRIPTION
In order to provide the best possible combination to driveablity, 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 values are out of threshold value, the PCM determines that a fault exists and a DTC is stored.
DTC Detecting Condition:
MONITOR SCANTOOL DATA
1. Ignition "OFF
2. Connect Scantool and Engine "ON"
3. Monitor HO2S parameter and parameters related to Fuel System Too Lean on CURRENT DATA.
4. Are the parameters related to Fuel System Too Lean displayed within specifications?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Check Sensors and Injectors related to this Fuel System Too Lean according to the troubleshoting Guide. Repair or replace as necessary and Go to "System Inspection" procedure.
SYSTEM INSPECTION
1. Check Air Cleaner Restrictions
1. Visually/physically inspect the air Cleaner restrictions
1. If OK, go to "Fuel Pressure Test" as below.
2. If NG, repair as necessary and go to "Verification of Vehicle Repair" procedure.
2. Fuel Pressure Test
NOTE:
1. Be cautious that Fuel is explosive and an empty fuel tank can still contain explosive gases. When working on fuel system make sure to supply adequate ventilation to the work area. Do not smoke, and keep sparks and open flames away
2. The fuel system remains under pressure when the engine is not running. Release fuel system pressure before disconnecting any fuel line to reduce the chance of personal injury or fire damage to vehicle components.
1. Check the fuel for excessive water, alcohol, or other contaminants. Replace contaminated fuel as necessary.
2. Install the fuel pressure gauge to the fuel pressure gauge adaptor.
3. Apply battery voltage to the terminal for the pump drive and activate the fuel pump: then, with fuel pressure applied, check that there is no fuel leakage from the pressure gauge or connection part.
4. Disconnect the vacuum hose from the pressure regulator, and plug the hose end. Measure the fuel pressure at idle.
Specification: 320 - 340 kPa(3.26 - 3.47 kg/sq.cm, 46 - 49 psi)
5. Measure the fuel pressure when the vacuum hose is connected to the pressure regulator.
Specification: Approx. 255 kPa(2.57 kg/sq.cm, 37 psi)
6. Are the measured fuel pressure within specifications?
YES: Go to "Check injector leakage" as below.
NO: Repair or replace according to the below table. And then, go to "Verification of Vehicle Repair" procedure.
3. Check Injector Leakage
1. Ignition "OFF" after checking the Fuel Pressure Test.
2. Stop the engine and check for a change in the fuel pressure gauge reading for 5 minutes.
3. Does fuel pressure drop after engine is stopped?
YES:
- Substitute with a known - good PCM and check for proper operation.
- If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
NO: Repair or replace according to the below table. And then, go to "Verification of Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs.
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Monitor that all readiness tests have been verified as "Complete"
5. Are any DTCs present?
YES: Go to the applicable troubleshooting procedure.
NO: System is performing to specification at this time.