P0175
2GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0171: System Too Lean (Bank 1)
DTC P0171 - System Too Lean (Bank 1)
DTC P0172 - System Too Rich (Bank 1)
DTC P0174 - System Too Lean (Bank 2)
DTC P0175 - System Too Rich (Bank 2)
DESCRIPTION
The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim consists of both the short-term and the long-term fuel trims.
The short-term fuel trim is fuel compensation that is used to constantly maintain the air-fuel ratio at stoichiometric levels. The signal from the Air-Fuel Ratio (A/F) sensor indicates whether the air-fuel ratio is rich or lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air-fuel ratio is rich and an increase in the fuel injection volume if it is lean.
Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel term to vary from the central value. The long-term fuel trim, which controls overall fuel compensation, compensates for long-term deviations in the fuel trim from the central value caused by the short-term fuel trim compensation.
HINT:
- When DTC P0171 or P0174 is set, the actual air-fuel ratio is on the lean side. When DTC P0172 or P0175 is set, the actual air-fuel ratio is on the rich side.
- If the vehicle runs out of fuel, the air-fuel ratio is lean and DTC P0171 or P0174 may be set. The MIL is then illuminated.
- When the total of the short-term and long-term fuel trim values is within the malfunction threshold (and the engine coolant temperature is more than 75°C [167°F]), the system is functioning normally.
MONITOR DESCRIPTION
Under closed-loop fuel control, fuel injection volumes that deviate from those estimated by the ECM cause changes in the long-term fuel trim compensation value. The long-term fuel trim is adjusted when there are persistent deviations in the short-term fuel trim values. Deviations from the ECM's estimated fuel injection volumes also affect the average fuel trim learning value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learning value of the air-fuel ratio). If the average fuel trim learning value exceeds the malfunction threshold, the ECM interprets this as a fault in the fuel system and sets a DTC.
Example:
The average fuel trim learning value is +35% or more or -35% or less, the ECM interprets this as a fuel system malfunction.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
- Read freeze frame data using Techstream. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
- A low A/F sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run rich.
- A high A/F sensor voltage could be caused by a lean air-fuel mixture. Check for conditions that would cause the engine to run lean.
PROCEDURE
1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175)
(a) Connect Techstream to the DLC3.
(b) Turn the ignition switch ON and turn the tester ON.
(c) Select the following menu items: Powertrain / Engine and ECT / Trouble Code.
(d) Read DTCs.
Result:
HINT: If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.
B -- GO TO DTC CHART
A -- Continue to next step.
2. PERFORM ACTIVE TEST USING TECHSTREAM (A/F CONTROL)
(a) Connect Techstream to the DLC3.
(b) Start the engine and turn the tester ON.
(c) Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
(d) On the tester, select the following menu items: Powertrain / Engine and ECT / Active Test / Control the VVT System (Bank 1) or Control the VVT System (Bank 2).
(e) Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
(f) Monitor the output voltages of A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.
Result:
The A/F sensor reacts in accordance with increases and decreases in the fuel injection volume:
+25% = Rich output
Less than 3.0 V
-12.5% = Lean output
More than 3.35 V
NOTE: The A/F sensor has an output delay of a few seconds and the HO2 sensor has a maximum output delay of approximately 20 seconds.
- Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.
- To display the graph, select the following menu items on the tester: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS B1 S1 or AFS B2 S1 and O2S B1 S2 or O2S B2 S2 then press the graph button on the Data List view.
Result:
C -- PERFORM CONFIRMATION DRIVING PATTERN
B -- INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE)
A -- Continue to next step.
3. READ VALUE USING TECHSTREAM (MAF)
(a) Read the value using the Techstream (MAF).
NOTICE:
- Turn off the engine.
- Perform the inspection with the vehicle indoors and on a level surface.
- Perform the inspection of the MAF meter while it is installed to the air cleaner case (installed to the vehicle).
- During the test, do not use the exhaust air duct to perform suction on the exhaust pipe.
(1) Turn the ignition switch to ACC.
(2) Turn the ignition switch to ON (do not run the engine).
(3) Turn the tester ON.
(4) Select the following menu items: Powertrain / Engine and ECT / Data List / MAF.
(5) Wait 30 seconds, and read the values on the Techstream.
Standard condition:
Less than 0.55 g/sec.
NG -- REPLACE MASS AIR FLOW METER
OK -- Continue to next step.
4. READ VALUE USING TECHSTREAM (COOLANT TEMP)
(a) Connect Techstream to the DLC3.
(b) Turn the ignition switch ON and turn the tester ON.
(c) Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp.
(d) Read the COOLANT TEMP twice, when the engine is both cold and warmed up.
Standard:
With cold engine: Same as ambient air temperature.
With warm engine: Between 75°C and 100°C (167°F and 212°F).
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- Continue to next step.
5. CHECK PCV HOSE CONNECTIONS
(a) Check for PCV hose connections.
OK:
PCV hose is connected correctly and is not damaged.
NG -- REPAIR OR REPLACE PCV HOSE
OK -- Continue to next step.
6. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leakage.
OK:
No leakage from air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
7. CHECK FOR SPARKS AND IGNITION
Testing and Inspection
NG -- REPAIR OR REPLACE IGNITION SYSTEM
OK -- Continue to next step.
8. CHECK FOR EXHAUST GAS LEAK
(a) Check for exhaust gas leakage.
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST SYSTEM
OK -- Continue to next step.
9. CHECK FUEL PRESSURE
(a) Check the fuel pressure Testing and Inspection.
Standard pressure:
304 to 343 kPa (3.1 to 3.5 kgf/cm2, 44.1 to 49.7 psi)
NG -- REPAIR OR REPLACE FUEL SYSTEM
OK -- Continue to next step.
10. INSPECT FUEL INJECTOR (INJECTION AND VOLUME)
(a) Check the injection volume Testing and Inspection.
Standard injection volume:
45 to 58 cm3 (2.9 to 3.5 cu. in.) per 15 seconds
NG -- REPLACE FUEL INJECTOR
OK -- Continue to next step.
11. INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE) P0031
NG -- REPLACE AIR-FUEL RATIO SENSOR
OK -- Continue to next step.
12. INSPECT INTEGRATION RELAY (A/F RELAY) P0031
NG -- REPLACE INTEGRATION RELAY
OK -- Continue to next step.
13. CHECK WIRE HARNESS (A/F SENSOR - ECM) P2195
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
14. REPLACE AIR-FUEL RATIO SENSOR
NEXT -- Continue to next step.
15. PERFORM CONFIRMATION DRIVING PATTERN
(a) Connect Techstream to the DLC3.
(b) Turn the ignition switch ON and turn the tester ON.
(c) Clear DTCs DTC Check / Clear.
(d) Switch the ECM from normal mode to check mode using the tester Check Mode Procedure.
(e) Start the engine and warm it up with all the accessories switched OFF.
(f) Drive the vehicle at between 60 km/h and 120 km/h (38 mph and 75 mph) and at an engine speed of between 1,400 rpm and 3,200 rpm for 3 to 5 minutes.
HINT: If the system is still malfunctioning, the MIL will be illuminated during step (f).
NOTE: If the conditions in this test are not strictly followed, no malfunction will be detected.
NEXT -- Continue to next step.
16. CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175)
(a) On Techstream, select the following menu items: Powertrain / Engine and ECT / Trouble Code.
(b) Read DTCs.
Result:
B -- READ VALUE USING TECHSTREAM (MAF)
A -- END