- PCV valve and hose
- PCV hose connections
- Fuel injector assembly blockage
- Gas leak from exhaust system
- Intake system
- Fuel pressure
- Mass air flow meter sub-assembly
- Engine coolant temperature sensor
| Last Modified: 05-13-2024 | 6.11:8.1.0 | Doc ID: RM100000001HT36 |
| Model Year Start: 2020 | Model: Corolla | Prod Date Range: [03/2019 - 11/2022] |
| Title: 2ZR-FAE (ENGINE CONTROL): SFI SYSTEM: P0171,P0172; System Too Lean (Bank 1); 2020 - 2023 MY Corolla [03/2019 - 11/2022] | ||
|
DTC |
P0171 |
System Too Lean (Bank 1) |
|
DTC |
P0172 |
System Too Rich (Bank 1) |
DESCRIPTION
The fuel trim is related to the feedback compensation value, not to the basic injection duration. The fuel trim consists of both the short-term and 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 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 lean.
Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel trim 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.
|
DTC No. |
Detection Item |
DTC Detection Condition |
Trouble Area |
MIL |
Memory |
Note |
|---|---|---|---|---|---|---|
|
P0171 |
System Too Lean (Bank 1) |
With a warm engine and stable air fuel ratio feedback, the fuel trim is considerably in error to the lean side (2 trip detection logic). |
|
Comes on |
DTC stored |
DTC for Mexico Models - Applies |
|
P0172 |
System Too Rich (Bank 1) |
With a warm engine and stable air fuel ratio feedback, the fuel trim is considerably in error to the rich side (2 trip detection logic). |
|
Comes on |
DTC stored |
DTC for Mexico Models - Applies |
HINT:
- When DTC P0171 is stored, the actual air fuel ratio is on the lean side. When DTC P0172 is stored, 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 may be stored. 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 higher 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 fuel injection volumes estimated by the ECM also affect the average fuel trim learned value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learned value of the air fuel ratio). If the average fuel trim learned value exceeds the malfunction thresholds, the ECM interprets this as a fault in the fuel system and stores a DTC.
Example:
-
except Mexico models
The average fuel trim learned value is +35% or higher, or -35% or less, the ECM interprets this as a fuel system malfunction.
-
for Mexico models
The average fuel trim learned value is +48% or higher, or -35% or less, the ECM interprets this as a fuel system malfunction.
MONITOR STRATEGY
|
Related DTCs |
P0171: Fuel trim lean P0172: Fuel trim rich |
|
Required Sensors/Components (Main) |
Fuel system |
|
Required Sensors/Components (Related) |
Air fuel ratio sensor Mass air flow meter sub-assembly Crank position sensor |
|
Frequency of Operation |
Continuous |
|
Duration |
Within 10 seconds |
|
MIL Operation |
2 driving cycles |
|
Sequence of Operation |
None |
TYPICAL ENABLING CONDITIONS
|
Monitor runs whenever the following DTCs are not stored |
P0010 (Camshaft timing oil control valve) P0011 (VVT system - advance) P0012 (VVT system - retard) P0013 (Exhaust camshaft timing oil control valve) P0014 (Exhaust VVT system - advance) P0015 (Exhaust VVT system - retard) P0016 (VVT system - misalignment) P0017 (Exhaust VVT system - misalignment) P0031, P0032 (Air fuel ratio sensor heater) P0102, P0103 (Mass air flow meter) P0107, P0108 (Manifold absolute pressure) P0115, P0117, P0118 (Engine coolant temperature sensor) P0120, P0121, P0122, P0123, P0220, P0222, P0223, P2135 (Throttle position sensor) P0125 (Insufficient coolant temperature for closed loop fuel control) P0335 (Crank position sensor) P0340, P0342, P0343 (Cam position sensor) P0365, P0367, P0368 (Exhaust cam position sensor) P0500 (Vehicle speed sensor) P219A, P219C, P219D, P219E, P219F (Air-fuel ratio imbalance) P264A, P2646, P2647, P1055, P10A0, P2648, P2649, P1049, P104A, U011B (Rocker arm control module) |
|
Fuel system status |
Closed loop |
|
Battery voltage |
11 V or higher |
|
Either of the following conditions is met |
1 or 2 |
|
1. Engine speed |
Less than 720 rpm |
|
2. Engine load |
13% or more |
|
Catalyst monitor |
Not executed |
TYPICAL MALFUNCTION THRESHOLDS
|
EVAP purge-cut |
Executing |
|
Either of the following conditions is met |
1 or 2 |
|
1. Average between short-term fuel trim and long-term fuel trim |
35% or higher (varies with engine coolant temperature) (except Mexico models) 48% or higher (varies with engine coolant temperature) (for Mexico models) |
|
2. Average between short-term fuel trim and long-term fuel trim |
-35% or less (varies with engine coolant temperature) |
CONFIRMATION DRIVING PATTERN
- Connect the Techstream to the DLC3.
- Turn the ignition switch to ON.
- Turn the Techstream on.
- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
- Turn the ignition switch off and wait for at least 30 seconds.
- Turn the ignition switch to ON [A].
- Turn the Techstream on.
- Start the engine and warm it up (until the engine coolant temperature 75°C (167°F) or higher) with all the accessories switched off [B].
- With the engine warmed up, idle the engine for 2 minutes or more [C].
-
Drive the vehicle at a speed between 60 and 135 km/h (37 and 84 mph) for 5 minutes or more [D].
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
- Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
-
Read the pending DTCs.
HINT:
If a pending DTC is output, the system is malfunctioning.
-
If on pending DTC is output, perform a universal trip and check for permanent DTCs.
Click here
![2020 - 2022 MY Corolla [03/2019 - 09/2022]; 2ZR-FAE (ENGINE CONTROL): SFI SYSTEM: DTC CHECK / CLEAR](/t3Portal/stylegraphics/info.gif)
HINT:
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.
WIRING DIAGRAM
-
Refer to DTC P0031 for the air fuel ratio sensor circuit.
Click here
-
Refer to DTC P0102 for the mass air flow meter sub-assembly circuit.
Click here
CAUTION / NOTICE / HINT
NOTICE:
Inspect the fuses for circuits related to this system before performing the following procedure.
HINT:
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.
- A low air fuel ratio sensor voltage could be caused by a rich air fuel mixture. Check for conditions that would cause the engine to run rich.
- A high air fuel ratio sensor voltage could be caused by a lean air fuel mixture. Check for conditions that would cause the engine to run lean.
- Read Freeze Frame Data using the Techstream. The ECM records vehicle and driving condition information as Freeze Frame Data the moment a DTC is stored. 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.
PROCEDURE
|
1. |
CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171 OR P0172) |
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(e) Read the DTCs.
Powertrain > Engine and ECT > Trouble Codes
|
Result |
Proceed to |
|---|---|
|
DTC P0171 or P0172 is output |
A |
|
DTC P0171 or P0172 and other DTCs are output |
B |
HINT:
If any DTCs other than P0171 or P0172 are output, troubleshoot those DTCs first.
| B |
|
GO TO DTC CHART
|
|
|
2. |
CHECK PCV HOSE CONNECTIONS |
(a) Check the PCV hose connections.
Click here
OK:
PCV valve and hose are connected correctly and are not damaged.
| NG |
|
REPAIR OR REPLACE PCV HOSE |
|
|
3. |
CHECK INTAKE SYSTEM |
(a) Check the intake system for vacuum leaks.
Click here
OK:
No leaks in intake system.
HINT:
Perform "Inspection After Repair" after repairing or replacing the intake system.
Click here
| NG |
|
REPAIR OR REPLACE INTAKE SYSTEM |
|
|
4. |
PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) |
(a) Connect the Techstream to the DLC3.
(b) Start the engine.
(c) Turn the Techstream on.
(d) Warm up the engine and run the engine at an engine speed of 2500 rpm for 90 seconds.
(e) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / Coolant Temp, AFS Voltage B1S1 and O2S B1S2.
Powertrain > Engine and ECT > Active Test
|
Active Test Display |
|---|
|
Control the Injection Volume for A/F Sensor |
|
Data List Display |
|---|
|
Coolant Temp |
|
AFS Voltage B1S1 |
|
O2S B1S2 |
(f) Change the fuel injection volume using the Techstream, and monitor the output voltage of the air fuel ratio sensor (AFS Voltage B1S1) and heated oxygen sensor (O2S B1S2) displayed on the Techstream.
HINT:
- The Active Test "Control the Injection Volume for A/F Sensor" can be used to lower the fuel injection volume by 12.5% or increase the injection volume by 12.5%.
- The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
- If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.
Standard:
|
Techstream Display (Sensor) |
Injection Volume |
Status |
Voltage |
|---|---|---|---|
|
AFS Voltage B1S1 (Air fuel ratio) |
12.5% |
Rich |
Below 3.1 V |
|
-12.5% |
Lean |
Higher than 3.4 V |
|
|
O2S B1S2 (Heated oxygen) |
12.5% |
Rich |
Higher than 0.55 V |
|
-12.5% |
Lean |
Below 0.4 V |
|
Status AFS Voltage B1S1 |
Status O2S B1S2 |
Air Fuel Ratio Condition and Air Fuel Ratio Sensor Condition |
Suspected Trouble Area |
Proceed to |
|---|---|---|---|---|
|
Lean/Rich |
Lean/Rich |
Normal |
- |
A |
|
Lean |
Lean |
Actual air fuel ratio lean |
|
|
|
Rich |
Rich |
Actual air fuel ratio rich |
|
|
|
Lean |
Lean/Rich |
Air fuel ratio sensor malfunction |
Air fuel ratio sensor |
B |
|
Rich |
Lean/Rich |
Air fuel ratio sensor malfunction |
Air fuel ratio sensor |
- Lean: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.
- Rich: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently below 3.1 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently higher than 0.55 V.
- Lean/Rich: While performing the Active Test "Control the Injection Volume for A/F Sensor", the output voltage of the fuel ratio sensor (AFS Voltage B1S1) or heated oxygen sensor (O2S B1S2) alternates correctly.
HINT:
Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2].
Click here
| B |
|
|
|
5. |
READ VALUE USING TECHSTREAM (COOLANT TEMP) |
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.
Powertrain > Engine and ECT > Data List
|
Tester Display |
|---|
|
Coolant Temp |
(e) Read the Data List twice, when the engine is both cold and warmed up.
Standard:
|
Techstream Display |
Condition |
Specified Condition |
|---|---|---|
|
Coolant Temp |
Cold engine |
Same as ambient air temperature |
|
Warm engine |
Between 75 and 100°C (167 and 212°F) |
HINT:
Perform "Inspection After Repair" after replacing the engine coolant temperature sensor.
Click here
| NG |
|
REPLACE ENGINE COOLANT TEMPERATURE SENSOR
|
|
|
6. |
READ VALUE USING TECHSTREAM (MAF) |
(a) Connect the Techstream to the DLC3.
(b) Start the engine.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / MAF, Coolant Temp and Engine Speed.
Powertrain > Engine and ECT > Data List
|
Tester Display |
|---|
|
Engine Speed |
|
MAF |
|
Coolant Temp |
(e) Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
(f) Read MAF with the engine speed at 3000 rpm.
Standard:
|
Techstream Display |
Condition |
Specified Condition |
|---|---|---|
|
MAF |
|
Between 5.0 and 10.0 gm/sec |
| NG |
|
|
|
7. |
CHECK FUEL PRESSURE |
(a) Check the fuel pressure.
Click here
| NG |
|
REPAIR OR REPLACE FUEL SYSTEM |
|
|
8. |
CHECK FOR EXHAUST GAS LEAK |
(a) Check for exhaust gas leaks.
OK:
No gas leaks in exhaust system.
HINT:
Perform "Inspection After Repair" after repairing or replacing the exhaust system.
Click here
| NG |
|
REPAIR OR REPLACE EXHAUST SYSTEM |
|
|
9. |
INSPECT IGNITION SYSTEM |
(a) Inspect the ignition system.
Click here
HINT:
- If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).
-
Perform "Inspection After Repair" after repairing or replacing the ignition system.
Click here
| NG |
|
REPAIR OR REPLACE IGNITION SYSTEM |
|
|
10. |
INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME) |
(a) Check the injection and volume.
HINT:
-
Refer to the fuel injector assembly inspection procedure.
Click here
- If the fuel injector assemblies malfunction, engine misfire may occur. The misfire count can be read using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Cylinder #1 Misfire Count (to Cylinder #4 Misfire Count).
-
Perform "Inspection After Repair" after replacing the fuel injector assembly.
Click here
| OK |
|
| NG |
|
REPLACE FUEL INJECTOR ASSEMBLY
|
|
11. |
INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) |
(a) Inspect the air fuel ratio sensor.
Click here
HINT:
Perform "Inspection After Repair" after replacing the air fuel ratio sensor.
Click here
| NG |
|
|
|
12. |
CHECK TERMINAL VOLTAGE (POWER SOURCE OF AIR FUEL RATIO SENSOR) |
|
(a) Disconnect the air fuel ratio sensor connector. |
|
(b) Turn the ignition switch to ON.
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
C55-2 (+B) - Body ground |
Ignition switch ON |
11 to 14 V |
| NG |
|
REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - EFI-MAIN RELAY) |
|
|
13. |
CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM) |
(a) Disconnect the air fuel ratio sensor connector.
(b) Disconnect the ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
C55-1 (HA1A) - C77-27 (HA1A) |
Always |
Below 1 Ω |
|
C55-3 (A1A+) - C77-100 (A1A+) |
Always |
Below 1 Ω |
|
C55-4 (A1A-) - C77-132 (A1A-) |
Always |
Below 1 Ω |
|
C55-1 (HA1A) or C77-27 (HA1A) - Body ground and other terminals |
Always |
10 kΩ or higher |
|
C55-3 (A1A+) or C77-100 (A1A+) - Body ground and other terminals |
Always |
10 kΩ or higher |
|
C55-4 (A1A-) or C77-132 (A1A-) - Body ground and other terminals |
Always |
10 kΩ or higher |
| NG |
|
REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
|
14. |
REPLACE AIR FUEL RATIO SENSOR |
(a) Replace the air fuel ratio sensor.
Click here
HINT:
Perform "Inspection After Repair" after replacing the air fuel ratio sensor.
Click here
|
|
15. |
CLEAR DTC |
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Clear the DTCs.
Powertrain > Engine and ECT > Clear DTCs
(e) Turn the ignition switch off and wait for at least 30 seconds.
|
|
16. |
CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172) |
(a) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
(b) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(c) Read the DTCs.
Powertrain > Engine and ECT > Trouble Codes
|
Result |
Proceed to |
|---|---|
|
DTCs are not output |
A |
|
DTC P0171 or P0172 is output |
B |
| A |
|
END |
|
|
17. |
READ VALUE USING TECHSTREAM (MAF) |
(a) Connect the Techstream to the DLC3.
(b) Start the engine.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / MAF, Coolant Temp and Engine Speed.
Powertrain > Engine and ECT > Data List
|
Tester Display |
|---|
|
Engine Speed |
|
MAF |
|
Coolant Temp |
(e) Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
(f) Read MAF with the engine speed at 3000 rpm.
Standard:
|
Techstream Display |
Condition |
Specified Condition |
|---|---|---|
|
MAF |
|
Between 5.0 and 10.0 gm/sec |
|
|
18. |
CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY CONNECTOR CONNECTION) |
(a) Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter sub-assembly and ECM.
Click here
HINT:
Repair any problems.
|
|
19. |
CLEAR DTC |
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Clear the DTCs.
Powertrain > Engine and ECT > Clear DTCs
(e) Turn the ignition switch off and wait for at least 30 seconds.
|
|
20. |
CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172) |
(a) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
(b) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(c) Read the DTCs.
Powertrain > Engine and ECT > Trouble Codes
|
Result |
Proceed to |
|---|---|
|
DTCs are not output |
A |
|
DTC P0171 or P0172 is output |
B |
| A |
|
END |
|
|
21. |
CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY - ECM) |
(a) Disconnect the mass air flow meter sub-assembly connector.
(b) Disconnect the ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
C26-1 (FG) - C77-137 (VG) |
Always |
Below 1 Ω |
|
C26-2 (E2G) - C77-104 (E2G) |
Always |
Below 1 Ω |
|
C26-3 (VCC) - C77-103 (VCVG) |
Always |
Below 1 Ω |
|
C26-1 (FG) or C77-137 (VG) - Body ground and other terminals |
Always |
10 kΩ or higher |
|
C26-3 (VCC) or C77-103 (VCVG) - Body ground and other terminals |
Always |
10 kΩ or higher |
| NG |
|
REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
|
22. |
REPLACE MASS AIR FLOW METER SUB-ASSEMBLY |
(a) Replace the mass air flow meter sub-assembly.
Click here
HINT:
- If the result of the inspection performed in step 6 and 17 (READ VALUE USING TECHSTREAM (MAF)) indicated no problem, proceed to the next step without replacing the mass air flow meter sub-assembly.
-
Perform "Inspection After Repair" after replacing the mass air flow meter sub-assembly.
Click here
|
|
23. |
CLEAR DTC |
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Clear the DTCs.
Powertrain > Engine and ECT > Trouble Codes
(e) Turn the ignition switch off and wait for at least 30 seconds.
|
|
24. |
CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172) |
(a) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
(b) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(c) Read the DTCs.
Powertrain > Engine and ECT > Trouble Codes
|
Result |
Proceed to |
|---|---|
|
DTCs are not output |
A |
|
DTC P0171 or P0172 is output |
B |
| A |
|
END |
| B |
|
REPLACE ECM
|
|
|