DESCRIPTION
WIRING DIAGRAM
INSPECTION PROCEDURE
CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175)
CHECK PCV HOSE CONNECTIONS
CHECK AIR INDUCTION SYSTEM
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (A/F CONTROL)
READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)
READ VALUE USING INTELLIGENT TESTER (MAF)
CHECK FUEL PRESSURE
CHECK FOR EXHAUST GAS LEAKS
CHECK FOR SPARKS AND IGNITION
INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME)
INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
INSPECT ENGINE ROOM JUNCTION BLOCK (A/F SENSOR HEATER RELAY)
CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
REPLACE AIR FUEL RATIO SENSOR
PERFORM CONFIRMATION DRIVING PATTERN
CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175)
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 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 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.If both the short-term and long-term fuel trims are lean or rich beyond predetermined values, it is interpreted as a malfunction, and the ECM illuminates the MIL and sets a DTC.DTC No.
| DTC Detection Conditions
| Trouble Areas
|
P0171
P0174
| With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to lean side (2 trip detection logic)
| - Air induction system
- Injector blockage
- Mass Air Flow (MAF) meter
- Engine Coolant Temperature (ECT) sensor
- Fuel pressure
- Gas leakage from exhaust system
- Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
- A/F sensor (bank 1, 2 sensor 1)
- A/F sensor heater (bank 1, 2 sensor 1)
- A/F sensor heater relay
- A/F sensor heater and A/F sensor heater relay circuits
- PCV valve and hose
- PCV hose connections
- ECM
|
P0172
P0175
| With warm engine and stable air-fuel ratio feedback, fuel trim considerably in error to rich side (2 trip detection logic)
| - Injector leakage or blockage
- MAF meter
- ECT sensor
- Ignition system
- Fuel pressure
- Gas leakage from exhaust system
- Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
- A/F sensor (bank 1, 2 sensor 1)
- A/F sensor heater (bank 1, 2 sensor 1)
- A/F sensor heater relay
- A/F sensor heater and A/F sensor heater relay circuits
- ECM
|
- 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.
WIRING DIAGRAM
Refer to DTC P2195 (Link).
INSPECTION PROCEDURE
- HINT:
- For use of the intelligent tester only:
- Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the Air-Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.
- The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using the intelligent tester.
- Connect the intelligent tester to the DLC3.
- Start the engine and turn the tester on.
- Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
- Select the following menu items on the tester: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.
- 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).
- Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.
- HINT:
- The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
- Standard voltage:
Tester Display (Sensor)
| Injection Volumes
| Status
| Voltages
|
AFS B1S1 or AFS B2S1 (A/F)
| +25%
| Rich
| Less than 3.0
|
AFS B1S1 or AFS B2S1 (A/F)
| -12.5%
| Lean
| More than 3.35
|
O2S B1S2 or O2S B2S2 (HO2)
| +25%
| Rich
| More than 0.55
|
O2S B1S2 or O2S B2S2 (HO2)
| -12.5%
| Lean
| Less than 0.4
|
- NOTICE:
- The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum delay of approximately 20 seconds.
Case
| A/F Sensor (Sensor 1)
Output Voltage
| HO2 Sensor (Sensor 2)
Output Voltage
| Main Suspected Trouble Area
|
1
| Injection Volume
+25%
-12.5%
| 
| Injection Volume
+25%
-12.5%
|
| -
|
Output Voltage
More than 3.35 V
Less than 3.0 V
| 
| Output Voltage
More than 0.55 V
Less than 0.4 V
| 
|
2
| Injection Volume
+25%
-12.5%
|
| Injection Volume
+25%
-12.5%
|
| - A/F sensor
- A/F sensor heater
- A/F sensor circuit
|
Output Voltage
Almost
no reaction
| 
| Output Voltage
More than 0.55 V
Less than 0.4 V
|
|
3
| Injection Volume
+25%
-12.5%
|
| Injection Volume
+25%
-12.5%
|
| - HO2 sensor
- HO2 sensor heater
- HO2 sensor circuit
|
Output Voltage
More than 3.35 V
Less than 3.0 V
|
| Output Voltage
Almost
no reaction
|
|
4
| Injection Volume
+25%
-12.5%
|
| Injection Volume
+25%
-12.5%
|
| - Injector
- Fuel pressure
- Gas leakage from exhaust system
(Air-fuel ratio extremely lean or rich)
|
Output Voltage
Almost
no reaction
|
| Output Voltage
Almost
no reaction
|
|
- 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.
- The following A/F Control procedure enables the technician to check and graph the voltage output of both the heated oxygen sensors. To display the graph, select the following menu items on the tester: View / Line Graph.
- HINT:
- Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
- 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.
| 1.CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174 OR P0175) |
Connect the intelligent tester to the DLC3.
Turn the ignition switch to the ON position and turn the tester on.
Select the following menu items: Powertrain / Engine / DTC.
Read the DTCs.
- Result:
Display (DTC Output)
| Proceed to
|
P0171, P0172, P0174 or P0175
| A
|
P0171, P0172, P0174 or P0175 and other DTCs
| B
|
- HINT:
- If any DTCs other than P0171, P0172, P0174 or P0175 are output, troubleshoot those DTCs first.
| 2.CHECK PCV HOSE CONNECTIONS |
- OK:
- PCV hose is connected correctly and is not damaged.
| | REPAIR OR REPLACE PCV HOSE |
|
|
| 3.CHECK AIR INDUCTION SYSTEM |
Check the air induction system for vacuum leakage.
- OK:
- No leakage from the air induction system.
| | REPAIR OR REPLACE AIR INDUCTION SYSTEM |
|
|
| 4.PERFORM ACTIVE TEST USING INTELLIGENT TESTER (A/F CONTROL) |
Connect the intelligent tester to the DLC3.
Start the engine and turn the tester on.
Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
Select the following menu items on the tester: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.
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).
Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.
- HINT:
- The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
- Standard voltage:
Tester Display (Sensor)
| Injection Volumes
| Status
| Voltages
|
AFS B1S1 or AFS B2S1 (A/F)
| +25%
| Rich
| Less than 3.0
|
AFS B1S1 or AFS B2S1 (A/F)
| -12.5%
| Lean
| More than 3.35
|
O2S B1S2 or O2S B2S2 (HO2)
| +25%
| Rich
| More than 0.55
|
O2S B1S2 or O2S B2S2 (HO2)
| -12.5%
| Lean
| Less than 0.4
|
- Result:
Status AFS B1S1 or AFS B2S1
| Status O2S B1S2 or O2S B2S2
| A/F Condition and A/F Sensor Condition
| Misfires
| Suspected Trouble Areas
| Proceed to
|
Lean/Rich
| Lean/Rich
| Normal
| -
| -
| C
|
Lean
| Lean
| Actual air-fuel ratio lean
| May occur
| - PCV valve and hose
- PCV hose connections
- Injector blockage
- Gas leakage from exhaust system
- Air induction system
- Fuel pressure
- Mass Air Flow (MAF) meter
- Engine Coolant Temperature (ECT) sensor
| A
|
Rich
| Rich
| Actual air-fuel ratio rich
| -
| - Injector leakage or blockage
- Gas leakage from exhaust system
- Ignition system
- Fuel pressure
- MAF meter
- ECT sensor
| A
|
Lean
| Lean/Rich
| A/F sensor malfunction
| -
| A/F sensor
| B
|
Rich
| Lean/Rich
| A/F sensor malfunction
| -
| A/F sensor
| B
|
Lean: During A/F CONTROL, the A/F sensor output voltage (AFS) is consistently more than 3.35 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V.
Rich: During A/F CONTROL, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.
Lean/Rich: During A/F CONTROL of the ACTIVE TEST, the output voltage of the heated oxygen sensor alternates correctly.
| 5.READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP) |
Connect the intelligent tester to the DLC3.
Turn the ignition switch to the ON position and turn the tester on.
Select the following menu items: Powertrain / Engine / Data List / Coolant Temp.
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 95°C (167°F and 203°F)
| 6.READ VALUE USING INTELLIGENT TESTER (MAF) |
Connect the intelligent tester to the DLC3.
Turn the ignition switch to the ON position and turn the tester on.
Select the following menu items: Powertrain / Engine / Data List / Coolant Temp.
Allow the engine to idle until the Coolant Temp reaches 75°C (167°F) or more.
Read the MAF with the engine in an idling condition and at an engine speed of 2,500 rpm.
- Standard:
- MAF while engine is idling:
- Between 3.2 g/s and 4.7 g/s (shift position: N, A/C: OFF).
- MAF at an engine speed of 2,500 rpm:
- Between 13.1 g/s and 18.9 g/s (shift position: N, A/C: OFF).
Check the fuel pressure (CAMRY_ACV40 RM000001IQZ005X_01_0002.html).
| | REPAIR OR REPLACE FUEL SYSTEM |
|
|
| 8.CHECK FOR EXHAUST GAS LEAKS |
- OK:
- No gas leakage.
| | REPAIR OR REPLACE EXHAUST SYSTEM |
|
|
| 9.CHECK FOR SPARKS AND IGNITION |
Check for sparks and ignition (CAMRY_ACV40 RM000000XH301MX_10_0006.html).
- HINT:
- If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the intelligent tester. Select the following menu items: Powertrain / Engine / Date List / Cylinder #1 (to 6) Misfire rate.
| | REPAIR OR REPLACE IGNITION SYSTEM |
|
|
| 10.INSPECT FUEL INJECTOR ASSEMBLY (INJECTION AND VOLUME) |
Inspect the fuel injector assembly (CAMRY_ACV40 RM000001IR1005X.html).
- HINT:
- If the injectors malfunction, engine misfire may occur. The misfire count can be read using the intelligent tester. Select the following menu items: Powertrain / Engine / Date List / Cylinder #1 (to 6) Misfire rate.
| 11.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) |
Disconnect the C15 or C35 A/F sensor connector.
Measure the resistance between the terminals of the A/F sensor connector.
- Standard resistance:
- Bank 1:
Tester Connection
| Specified Condition
|
HA1A (1) - +B (2)
| 1.8 to 3.4 Ω at 20°C (68°F)
|
HA1A (1) - A1A- (4)
| 10 kΩ or higher
|
- Bank 2:
Tester Connection
| Specified Condition
|
HA2A (1) - +B (2)
| 1.8 to 3.4 Ω at 20°C (68°F)
|
HA2A (1) - A2A- (4)
| 10 kΩ or higher
|
Reconnect the A/F sensor connector.
| 12.INSPECT ENGINE ROOM JUNCTION BLOCK (A/F SENSOR HEATER RELAY) |
Remove the engine room junction block from the engine room R/B.
Measure the A/F relay resistance.
- Standard resistance:
Tester Connection
| Specified Condition
|
1G-1 - 1A-4
| 10 kΩ or higher
|
1G-1 - 1A-4
| Below 1 Ω
(when battery voltage applied to terminals 1E-6 and 1E-11)
|
Reinstall the engine room junction block.
| | REPLACE ENGINE ROOM JUNCTION BLOCK |
|
|
| 13.CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) |
Disconnect the C15 or C35 A/F sensor connector.
Turn the ignition switch to the ON position.
Measure the voltage between the +B terminal of the A/F sensor connector and body ground.
- Standard voltage:
Tester Connection
| Specified Condition
|
+B (C15-2) - Body ground
| 9 to 14 V
|
+B (C35-2) - Body ground
| 9 to 14 V
|
Turn the ignition switch off.
Disconnect the C58 (RHD) or C55 (LHD) ECM connector.
Measure the resistance.
- Standard resistance (Check for open):
- RHD:
Tester Connection
| Specified Condition
|
HA1A (C15-1) - HA1A (C58-86)
| Below 1 Ω
|
A1A+ (C15-3) - A1A+ (C58-93)
| Below 1 Ω
|
A1A- (C15-4) - A1A- (C58-116)
| Below 1 Ω
|
HA2A (C35-1) - HA2A (C58-109)
| Below 1 Ω
|
A2A+ (C35-3) - A2A+ (C58-120)
| Below 1 Ω
|
A2A- (C35-4) - A2A- (C58-119)
| Below 1 Ω
|
- LHD:
Tester Connection
| Specified Condition
|
HA1A (C15-1) - HA1A (C55-86)
| Below 1 Ω
|
A1A+ (C15-3) - A1A+ (C55-93)
| Below 1 Ω
|
A1A- (C15-4) - A1A- (C55-116)
| Below 1 Ω
|
HA2A (C35-1) - HA2A (C55-109)
| Below 1 Ω
|
A2A+ (C35-3) - A2A+ (C55-120)
| Below 1 Ω
|
A2A- (C35-4) - A2A- (C55-119)
| Below 1 Ω
|
- Standard resistance (Check for short):
- RHD:
Tester Connection
| Specified Condition
|
HA1A (C15-1) or HA1A (C58-86) - Body ground
| 10 kΩ or higher
|
A1A+ (C15-3) or A1A+ (C58-93) - Body ground
| 10 kΩ or higher
|
A1A- (C15-4) or A1A- (C58-116) - Body ground
| 10 kΩ or higher
|
HA2A (C35-1) or HA2A (C58-109) - Body ground
| 10 kΩ or higher
|
A2A+ (C35-3) or A2A+ (C58-120) - Body ground
| 10 kΩ or higher
|
A2A- (C35-4) or A2A- (C58-119) - Body ground
| 10 kΩ or higher
|
- LHD:
Tester Connection
| Specified Condition
|
HA1A (C15-1) or HA1A (C55-86) - Body ground
| 10 kΩ or higher
|
A1A+ (C15-3) or A1A+ (C55-93) - Body ground
| 10 kΩ or higher
|
A1A- (C15-4) or A1A- (C55-116) - Body ground
| 10 kΩ or higher
|
HA2A (C35-1) or HA2A (C55-109) - Body ground
| 10 kΩ or higher
|
A2A+ (C35-3) or A2A+ (C55-120) - Body ground
| 10 kΩ or higher
|
A2A- (C35-4) or A2A- (C55-119) - Body ground
| 10 kΩ or higher
|
Reconnect the ECM connector.
Reconnect the A/F sensor connector.
| | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
|
| 14.REPLACE AIR FUEL RATIO SENSOR |
Replace the air fuel ratio sensor (CAMRY_ACV40 RM000001OOL002X.html).
| 15.PERFORM CONFIRMATION DRIVING PATTERN |
Connect the intelligent tester to the DLC3 (Procedure A).
Turn the ignition switch to the ON position and turn the tester on (Procedure B).
Clear the DTCs (CAMRY_ACV40 RM000000PDK01VX.html) (Procedure C).
Select the check mode using the tester (CAMRY_ACV40 RM000000PDL025X.html) (Procedure D).
Start the engine and warm it up with all the accessories switched off (Procedure E).
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 (Procedure F).
- HINT:
- If the system is still malfunctioning, the MIL will be illuminated during procedure "F".
- NOTICE:
- If the conditions in this test are not strictly followed, no malfunction will be detected.
| 16.CHECK WHETHER DTC OUTPUT RECURS (DTC P0171, P0172, P0174 OR P0175) |
Select the following menu items: Powertrain / Engine / DTC.
Read the DTCs.
- Result:
Display (DTC Output)
| Proceed to
|
No output
| A
|
P0171, P0172, P0174 or P0175
| B
|
