P0170
DTC P0170 FUEL TRIM (BANK 1)GENERAL DESCRIPTION
In order to provide the best possible combination of DRIVEABILITY, fuel economy and emission control, the ECM uses a closed loop air/fuel metering system. The ECM 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 ECM 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 ECM 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
If the fuel trim values reaches the maximum or minimum threshold, then feedback control is no longer possible and emissions will be increased. The ECM sets DTC P0170 if no proportional fuel adaptation occurs for a defined time after the short term fuel trim has reached its minimum or maximum threshold.
DTC Detecting Condition:
SIGNAL WAVEFORM AND DATA
1. Scan Tool Display for HO2S
2. Scan Tool Display for MAF
3. Scan Tool Display for TPS1 & TPS2
MONITOR DTC STATUS
NOTE: If any DTCs relating to INJECTOR, HO2S, ECTS, or MAFS are stored, do ALL REPAIRS associated with those codes before proceeding with further troubleshooting
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode.
2. Press F4 (DTAL) to select DTC information from the DTCs menu.
3. Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Read "DTC Status" parameter.
5. Is parameter displayed "History (Not Present) fault"?
NOTE:
- History (Not Present) fault : DTC occurred but has been cleared.
- Present fault : DTC is occurring at present time.
YES - Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM 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 - Go to next step as below
MONITOR ACTUATION TEST
NOTE: The main purpose of this test is to identify potential engine mechanical condition problems and fuel and ignition systems problems that are not common to all cylinders. For best results, perform this test while maintaining as steady an rpm reading as possible.
Caution: Before beginning tests; set the parking brake, place gear selector in P or N and block drive wheels for safety.
1. Warm up the engine to normal operating temperature and let it idle.
2. Install Scan Tool and select INJECTOR #1 parameter on the Actuation Test mode.
3. Monitor engine rpm and shut off the injector #1 by pressing "STRT (F1)" key.
4. Repeat procedure on all injectors and record the engine rpm.
Specification : All cylinders should show an even RPM drop.
5. Was each cylinder's rpm drop within the same value?
YES - Go to next step as below
NO - Cylinders with the least amount of RPM drop are not contributing their share of power. Go to "Fuel Injector Inspection" procedure and check the suspect cylinders
NOTE: If the RPM loss between cylinders is quite large (200 RPM or more) and engine has high mileage, there is possibility of engine wear. Perform compression test with pressure gauge to check the engine wear
CHECK INTAKE/EXHAUST SYSTEM FOR RESTRICTION OR LEAKAGE
1. Visually/physically inspect the air leakage in intake/exhaust system for the following areas:
- 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. Visually/physically inspect the restriction in intake/exhaust system for the following areas:
- Air cleaner filter element for excessive dirt or for any foreign objects
- Throttle body inlet for damage or for any foreign objects
- Throttle bore and throttle plate for chocking and for any foreign objects
- Restricted exhaust system
3. Was a problem found in any of the above areas?
YES - Replace or repair as necessary and go to "Verification of Vehicle Repair" procedure
NO - Go to next step as below
4. Inspect the leakage in EVAP. System for the following conditions:
1. Check the EVAP canister for fuel saturation. If the EVAP canister is full of fuel, visually and physically inspect the EVAP and fuel system. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure. If OK, go to next step.
2. Remove the manifold side vacuum hose from the EVAP canister purge valve.
3. Using a hand vacuum pump apply specified vacuum (Approx. 15 inHg) to the manifold side of the valve.
4. Does the valve hold vacuum?
YES - Go to next step as below
NO - Repair air leakage and go to "Verification of Vehicle Repair" procedure
SENSOR INSPECTION
NOTE: Refer to "Signal Waveform & Data" in the "General Information" procedure
1. Visually/physically inspect the HO2S for the following conditions:
- Ensure that the HO2S is securely installed.
- Silicon contamination. This contamination will be indicated by a white powdery coating on the portion of the sensor exposed to the exhaust stream and this will result in a but false (high) voltage signal.
- Fuel, engine coolant or oil contamination.
- Use of improper sealant.
2. Visually/physically inspect the MAFS for the following conditions:
- Contamination or deterioration.
- Poor connection or damaged harness.
3. Check for an intermittent TPS false signal. TPS signal displayed on a scantool should increase steadily when depressing accelerator pedal after starting.
4. Verify that the ECM ground connections are clean and properly tightened. C102
5. If test result is NG, repair or replace as necessary and go to "Verification of Vehicle Repair" procedure. If OK, go to next step as below.
NOTE: If the contamination is evident on the HO2S or MAFS. Fix the source of the sensor contamination before replacing the sensor to prevent future contamination.
POSITIVE CRANKCASE VENTILATION SYSTEM INSPECTION
1. Check the engine oil level. The oil level should be between the min. and max. marking. Fill to the correct oil level.
2. Check crankcase ventilation valve for improper installation, damaged O-rings and malfunctioning.
3. Warm up the engine to normal operating temperature.
4. Connect Scantool and note the "SHORT TERM FUEL-B1" parameter on the Scantool data list.
5. Disconnect and plug the positive crankcase ventilation at the intake manifold side.
6. Monitor the "SHORT TERM FUEL-B1" parameter on the Scantool data list once again.
Specification : The value should remain more or less unchanged
7. Is the displayed value within the specified value?
YES - Go to next step as below
NO - Check the PCV (Positive Crankcase Ventilation) valve for operation properly. Refer to "EM" group in Workshop Manual. If OK, check that engine oil is diluted with fuel. Change the oil or filter as necessary and go to "Verification of Vehicle Repair" procedure
FUEL SYSTEM INSPECTION
1. Fuel Line Pressure Inspection
1. Check the fuel for excessive water, alcohol, or other contaminants. Replace contaminated fuel as necessary.
2. Install a fuel pressure gage.
3. Inspect fuel pressure with normal idle status.
Specification : 338 - 348 kPa (3.45 - 3.55 kg/sq.cm)
4. Is fuel pressure within the specified value?
YES - Go to next step as below
NO - Inspect the suspected area. Refer to table as below. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
2. Fuel pressure hold inspection
1. Stop the engine and check for a change in the fuel pressure gauge reading.
Specification : After engine stops, the gauge reading should hold for minimum 5 minutes
2. Is fuel pressure within the specified value?
YES - Visually/physically inspect the engine mechanical problem for the following:
- Worn cylinder
- Worn valve
- Worn piston or piston ring
NO - Inspect the suspected area. Refer to table as below. Repair or replace as necessary and 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. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode.
2. Press F4 (DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
3. Read "DTC Status" parameter.
4. Is parameter displayed "History (Not Present) fault"?
YES - System performing to specification at this time. Clear the DTC
NO - Go to the applicable troubleshooting procedure.