dtc p0171 system too lean (bank 1)

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05-498
DIAGNOSTICS
-
SFI SYSTEM (3MZ-FE)
05EXR-06
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)
CIRCUIT DESCRIPTION
The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim includes the short-term fuel trim and the long-term fuel trim.
The short-term fuel trim is the short-term fuel compensation used to maintain the air-fuel ratio at the stoichiometric air-fuel ratio. The signal from the A/F sensor indicates whether the air-fuel ratio is RICH or LEAN
compared to the stoichiometric air-fuel ratio. This variance triggers a reduction in the fuel volume if the airfuel ratio is RICH, and an increase in the fuel volume if it is LEAN.
The short-term fuel trim varies from the central value due to individual engine differences, wear over time
and changes in the operating environment. The long-term fuel trim, which controls overall fuel compensation, steadies long-term deviations of the short-term fuel trim from the central value.
If both the short-term fuel trim and the long-term fuel trim are LEAN or RICH beyond a certain value, it is
detected as a malfunction and the MIL is illuminated and a DTC is set.
DTC No.
P0171
P0174
P0172
P0175
DTC Detection Condition
Trouble Area
When air-fuel ratio feedback is stable after warming up engine,
fuel trim is considerably in error on LEAN side
(2 trip detection logic)
Air induction system
Injector blockage
MAF meter
ECT sensor
Fuel pressure
Gas leakage in 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 relay
PCV valve and hose
PCV hose connection
When air-fuel ratio feedback is stable after warming up engine,
fuel trim is considerably in error on RICH side
(2 trip detection logic)
Injector leak, blockage
MAF meter
ECT sensor
Ignition system
Fuel pressure
Gas leakage in 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
A/F relay
HINT:
When DTC P0171 or P0174 is recorded, the actual air-fuel ratio is on the LEAN side. When DTC
P0172 or P0175 is recorded, 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 recorded.
The MIL then illuminates.
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
688
05-499
DIAGNOSTICS
-
SFI SYSTEM (3MZ-FE)
MONITOR DESCRIPTION
+35 (%): Threshold at LEAN
1.35
Fuel Compensation
Amount
1.0
-35 (%): Threshold at RICH
0.65
A82386
Under closed-loop fuel control, fuel injection amounts that deviate from the ECM’s estimated fuel amount
will cause a change in the long-term fuel trim compensation value. This long-term fuel trim is adjusted when
there are persistent deviations in the short-term fuel trim values. And the deviation from the simulated fuel
injection amount by the ECM affects a smoothed fuel trim learning value. The smoothed fuel trim learning
value is the combination of smoothed short-term fuel trim (fuel feedback compensation value) and
smoothed long-term fuel trim (learning value of the air-fuel ratio). When the smoothed fuel trim learning value exceeds the DTC threshold, the ECM interprets this as a fault in the fuel system and sets a DTC.
Example:
The smoothed fuel trim learning value is more than +35 % or less than -35 %. The ECM interprets this as
a failure in the fuel system.
MONITOR STRATEGY
Related DTCs
P0171: Fuel System Lean (Bank 1)
P0172: Fuel System Rich (Bank 1)
P0174: Fuel System Lean (Bank 2)
P0175: Fuel System Rich (Bank 2)
Required sensors / components (Main)
Fuel system
Required sensors / components (Related)
A/F sensor, MAF meter, CKP sensor
Frequency of operation
Continuous
Duration
10 seconds
MIL operation
2 driving cycles
Sequence operation
None
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
689
05-500
DIAGNOSTICS
-
SFI SYSTEM (3MZ-FE)
TYPICAL ENABLING CONDITIONS
The monitor will run whenever these DTCs are not present
See page 05-377
Battery voltage
11 V or more
Fuel system
Closed Loop
Throttle position learning
Completed
Either of the following conditions is met:
-
Engine RPM
Less than 1,100 rpm
Intake air amount
0.22 g/rev or more
TYPICAL MALFUNCTION THRESHOLDS
Fuel Trim Lean:
Smoothed fuel trim learning value
35 %* or more
Fuel Trim Rich:
Smoothed fuel trim learning value
-35 %* or more
HINT:
*: The threshold value varies with the ECT.
WIRING DIAGRAM
Refer to DTC P2195 on page 05-629 .
INSPECTION PROCEDURE
HINT:
Hand-held tester only:
It is possible the malfunctioning area can be found using the ACTIVE TEST A/F CONTROL operation. The
A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble
areas are malfunctioning or not.
(a) Perform the ACTIVE TEST A/F CONTROL operation.
HINT:
The A/F CONTROL operation lowers the injection volume by 12.5 % or increases the injection volume by
25 %.
(1) Connect the hand-held tester to the DLC3 on the vehicle.
(2) Turn the ignition switch ON.
(3) Warm up the engine by running the engine at 2,500 rpm for approximately 90 seconds.
(4) Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
(5) Perform the A/F CONTROL operation with the engine idling (press the right or left button).
Result:
A/F sensor reacts in accordance with increase and decrease of injection volume:
+25 % → RICH output: Less than 3.0 V
-12.5 % → LEAN output: More than 3.35 V
Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25 % → RICH output: More than 0.55 V
-12.5 % → LEAN output: Less than 0.4 V
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
690
05-501
DIAGNOSTICS
-
SFI SYSTEM (3MZ-FE)
NOTICE:
The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about
20 seconds of delay.
Output voltage of A/F sensor
(sensor 1)
Output voltage of heated oxygen
sensor (sensor 2)
Injection volume
Injection volume
+25 %
+25 %
-12.5 %
-12.5 %
Case 1 Output voltage
More than 3.35 V
Less than 3.0 V
OK
More than 0.55 V
Injection volume
+25 %
-12.5 %
-12.5 %
Case 2 Output voltage
A/F sensor
(A/F sensor, heater, A/F sensor circuit)
Output voltage
NG
Injection volume
More than 0.55 V
OK
Less than 0.4V
Injection volume
+25 %
+25 %
-12.5 %
-12.5 %
Case 3 Output voltage
Output voltage
More than 3.35 V
OK
Injection volume
Almost
No reaction
NG
Injection volume
+25 %
+25 %
-12.5 %
-12.5 %
Case 4 Output voltage
Almost
No reaction
OK
Less than 0.4V
+25 %
Less than 3.0V

Output voltage
Injection volume
Almost
No reaction
Mainly suspected
Trouble Area
Output voltage
NG
Almost
No reaction
NG
Heated oxygen sensor
(heated oxygen sensor,
heater, heated oxygen sensor
circuit)
Extremely rich or lean actual
air-fuel ratio
(Injector, fuel pressure, gas
leakage in exhaust system,
etc.)
The following A/F CONTROL procedure enables the technician to check and graph the voltage outputs of
both the A/F sensor and the heated oxygen sensor.
For displaying the graph, enter ”ACTIVE TEST / A/F CONTROL / USER DATA”, select ”AFS B1S1 and O2S
B1S2” by pressing ”YES” and push ”ENTER”. Then press ”F4”.
HINT:
Read freeze frame data using the hand−held tester or the OBD II scan tool. Freeze frame data records
the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can
help determine if the vehicle was running or stopped, 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 high A/F sensor voltage could be caused by a RICH air-fuel mixture. Check the conditions that would
cause the engine to run with a RICH air-fuel mixture.
A low A/F sensor voltage could be caused by a LEAN air-fuel mixture. Check the conditions that would
cause the engine to run with a LEAN air-fuel mixture.
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
691
05-502
DIAGNOSTICS
1
(a)
-
SFI SYSTEM (3MZ-FE)
CHECK AIR INDUCTION SYSTEM
Check for vacuum leaks in air induction system.
OK: No vacuum leak.
NG
REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK
2
CHECK CONNECTION OF PCV HOSE
OK: PCV hose is connected correctly, and PCV hose is not damaged.
NG
REPAIR OR REPLACE PCV HOSE
OK
3
INSPECT FUEL INJECTOR ASSY (INJECTION AND VOLUME) (See page 11-38 )
Standard:
Injection volume
Difference between each injector
60 to 73 cm3 (3.7 to 4.5 cu in.) per 15 seconds
13 cm3 (0.8 cu in.) or less
NG
REPLACE FUEL INJECTOR ASSY
(See page 11-46 )
OK
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
692
05-503
DIAGNOSTICS
4
-
SFI SYSTEM (3MZ-FE)
INSPECT MASS AIR FLOW METER
(a)
(b)
Air
E2
THA
5
VG
+B
E2G
4 3 2 1
(c)
30
20
10
Remove the MAF meter.
Check the output voltage.
(1) Apply battery voltage across terminals +B and E2G.
(2) Connect the positive (+) tester probe to terminal
VG, and negative (-) tester probe to terminal E2G.
(3) Blow air into the MAF meter, and check that the voltage fluctuates.
Check the resistance of the IAT sensor terminals.
Standard:
Tester Connection
Condition
Specified Condition
THA (4) - E2 (5)
-20 C (-4F)
13.6 to 18.4 kΩ
THA (4) - E2 (5)
20C (68F)
2.21 to 2.69 kΩ
THA (4) - E2 (5)
60C (140F)
0.49 to 0.67 kΩ
Resistance kΩ
5
3
2
1
0.5
0.3
0.2
Acceptable
0.1
-20
(-4)
0 20 40 60 80 100
(32) (80) (104) (140)(176) (212)
TemperatureC(F)
A60548
NG
REPLACE MASS AIR FLOW METER
OK
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
693
05-504
DIAGNOSTICS
5
-
SFI SYSTEM (3MZ-FE)
INSPECT ENGINE COOLANT TEMPERATURE SENSOR (RESISTANCE)
(a)
(b)
Ohmmeter
Remove the ECT sensor.
Check the resistance of the ECT sensor terminals.
Standard:
Tester Connection
Condition
Specified Condition
1-2
20C (68F)
2.32 to 2.59 kΩ
1-2
80C (176F)
0.310 to 0.326 kΩ
30
20
10
5
Resistance KΩ
Acceptable
3
2
1
0.5
0.3
0.2
0.1
-20
S01196
S01699
(-4)
0
20 40 60 80 100
NOTICE:
When checking the ECT sensor in the water, be careful not
to allow water to go into the terminals. After the check, dry
the sensor.
HINT:
Alternate procedure: Connect an ohmmeter to the installed
ECT sensor and read the resistance. Use an infrared thermometer to measure the engine temperature in the immediate vicinity of the sensor. Compare these values to the resistance/temperature graph. Change the engine temperature (warm up or
allow to cool down) and repeat the test.
(32) (68) (104) (140) (176) (212)
Temperature C (F)
A81700
NG
REPLACE ENGINE COOLANT TEMPERATURE
SENSOR
OK
6
CHECK FOR SPARK AND IGNITION (See page 18-7 )
OK: Spark occurs.
NG
REPAIR OR REPLACE
OK
7
(a)
CHECK FUEL PRESSURE (See page 11-38 )
Check the fuel pressure (high or low pressure).
Standard:
Fuel pressure: 304 to 343 kPa (3.1 to 3.5 kgf/cm2, 44 to 50 psi)
NG
REPLACE FUEL SYSTEM
OK
8
CHECK FOR EXHAUST GAS LEAKAGE
OK: No gas leak.
NG
REPAIR OR REPLACE EXHAUST
LEAKAGE POINT (See page 15-5 )
GAS
OK
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
694
05-505
DIAGNOSTICS
9
(a)
(b)
-
SFI SYSTEM (3MZ-FE)
READ VALUE OF HAND-HELD TESTER OR OBD II SCAN TOOL (OUTPUT VOLTAGE OF AIR FUEL RATIO SENSOR (BANK 1, 2 SENSOR 1))
Connect the hand-held tester or the OBD II scan tool to the DLC 3.
Warm up the A/F sensors (bank 1, 2 sensor 1) by running the engine at 2,500 rpm for approximately
90 seconds.
Read A/F sensor voltage output on the hand-held tester or the OBD II scan tool.
Hand-held tester only:
Enter the following menus: ENHANCED OBD II / SNAPSHOT / MANUAL SNAPSHOT / USER DATA.
Select ”AFS B1 S1 or AFS B2 S1/ENGINE SPD” and press YES.
Monitor the A/F sensor voltage carefully.
Check the A/F sensor voltage output under the following conditions:
(1) Allow engine to idle for 30 seconds.
(2) Running the engine at approximately 2,500 rpm (where engine RPM is not suddenly changed).
(3) Raise the engine speed to 4,000 rpm and quickly release the accelerator pedal so that the throttle
is fully closed.
Standard:
Condition (1) and (2)
Voltage change of 3.3 V (0.66 V)* (between approximately 3.1 to 3.5 V) as shown in the illustration.
Condition (3)
A/F sensor voltage increases to 3.8 V (0.76 V)* or more when fuel is cut during engine deceleration, as shown in the illustration.
(c)
(d)
(e)
(f)
(g)
HINT:
*: Voltage when using the OBD II scan tool.
Normal Condition
Malfunction Condition
(3) Approximately 4,000 rpm
(3) Approximately 4,000 rpm
(2) Approximately 2,500 rpm
(1) Idle
(2) Approximately 2,500 rpm
A/F
Sensor
Voltage
(1) Idle
(1) Idle
(1) Idle
Engine
RPM
Engine
RPM
”Condition (3)”
3.8 V or More
A/F
Sensor
Voltage
Fuel Cut
”Condition (1), (2)”
Change approximately 3.3 V
Fuel Cut
When A/F sensor circuit is malfunctioning,
voltage output does not change
A72304
HINT:
Whenever the output voltage of the A/F sensor remains at approximately 3.3 V (0.660 V)* (see ”Malfunction Condition” graphic) under any condition as well as the above conditions, the A/F sensor may
have an open circuit (this will happen also when the A/F sensor heater has an open circuit).
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
695
05-506
DIAGNOSTICS
-
SFI SYSTEM (3MZ-FE)
Whenever the output voltage of the A/F sensor remains at a certain value of approximately 3.8 V (0.76
V)* or more, or 2.8 V (0.56 V)* or less (see ”Malfunction Condition” graphic) under any condition as
well as the above conditions, the A/F sensor may have a short circuit.
The ECM will stop fuel injection (fuel cut) during engine deceleration. This will cause a LEAN condition
and should result in a momentary increase in A/F sensor voltage output.
The ECM must establish a closed throttle position learned value to perform fuel cut. If the battery terminal has been disconnected, the vehicle must be driven over 10 mph to allow the ECM to learn the
closed throttle position.
When the vehicle is driven:
The output voltage of the A/F sensor may be below 2.8 V (0.76 V)* during fuel enrichment. For the
vehicle, this translates to a sudden increase in speed with the accelerator pedal fully depressed when
trying to overtake another vehicle. The A/F sensor is functioning normally.
The A/F sensor is a current output element, and therefore the current is converted into voltage inside
the ECM. If measuring voltage at connectors of A/F sensor or ECM, you will observe a constant voltage.
*: Voltage when using the OBD II scan tool.
OK
Go to step 17
NG
10
INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
(a)
(b)
AF-
Disconnect the A6 or A7 A/F sensor connector.
Check the resistance of the A/F sensor terminals.
Standard:
Tester Connection
Condition
Specified Condition
1 (HT) - 2 (+B)
20C (68F)
1.8 to 3.4 Ω
1 (HT) - 4 (AF-)
-
10 kΩ or higher
AF+
A52607
NG
REPLACE AIR FUEL RATIO SENSOR
OK
11
INSPECT RELAY (A/F)
1
3
(a)
(b)
2
5
5
2
Remove the A/F relay from the engine room R/B No. 2.
Check the resistance of the A/F relay.
Standard:
Tester Connection
Specified Condition
3-5
10 kΩ or higher
3-5
Below 1 Ω
(when battery voltage is applied to terminals 1 and 2)
1
3
B60778
NG
REPLACE RELAY
OK
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
696
05-507
DIAGNOSTICS
12
-
SFI SYSTEM (3MZ-FE)
CHECK WIRE HARNESS (A/F SENSOR - ECM)
(a)
(b)
(c)
Wire Harness Side
HT
A6 (Bank 1)
A7 (Bank 2)
A/F Sensor
AF+
+B
Disconnect the A6 or A7 A/F sensor connector.
Disconnect the E8 ECM connector.
Check the resistance of the wire harness side connectors.
Standard:
Tester Connection
1 2
3 4
A6-3 (AF+) A6-4 (AF-) A6-1 (HT) A7-3 (AF+) A7-4 (AF-) A7-1 (HT) -
AF-
E8-22 (A1A+)
E8-30 (A1A-)
E8-5 (HA1H)
E8-23 (A2A+)
E8-31 (A2A-)
E8-4 (HA2A)
Below 1 Ω
A6-3 (AF+) or E8-22 (A1A+) - Body ground
A6-4 (AF-) or E8-30 (A1A-) - Body ground
A6-1 (HT) or E8-5 (HA1H) - Body ground
A7-3 (AF+) or E8-23 (A2A+) - Body ground
A7-4 (AF-) or E8-31 (A2A-) - Body ground
A7-1 (HT) or E8-4 (HA2A) - Body ground
E8
ECM
HA2A
HA1H
A2A+
Specified Condition
10 kΩ or higher
A1A+
A1AA2A-
Y
A76787
A81695
A85512
Reference (Bank 1 Sensor 1 System Drawing)
A/F Relay
From
Battery
A/F
ECM
A/F Sensor
+B
Heater
HT
HA1H
AF-
Sensor
AF+
A1A+
Duty
Control
A1AMREL
A87980
NG
REPAIR OR
CONNECTOR
REPLACE
HARNESS
AND
OK
13
REPLACE AIR FUEL RATIO SENSOR
GO
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
697
05-508
DIAGNOSTICS
14
-
SFI SYSTEM (3MZ-FE)
PERFORM CONFIRMATION DRIVING PATTERN
Vehicle Speed
(e)
60 to 120 km/h
(38 to 75 mph)
Idling
IG SW OFF
(d)
2 min.
3 to 5 min.
Time
(a), (b), (c)
A79199
(a)
Clear the DTCs.
(1) Disconnect the battery cable or remove the EFI NO. 1 and ETCS fuses for 60 seconds or more.
Connect the hand-held tester to the DLC3.
Switch the hand-held tester from the normal mode to the check mode (see page 05-402 ).
Start the engine and warm it up with all the accessory switches OFF.
Drive the vehicle at 60 to 120 km/h (38 to 75 mph) and engine speed at 1,400 to 3,200 rpm for 3 to
5 minutes.
(b)
(c)
(d)
(e)
HINT:
If a malfunction exists, the MIL will be illuminated during step (e).
NOTICE:
If the conditions in this test are not strictly followed, detection of a malfunction will not occur. If you
do not have a hand-held tester, turn the ignition switch OFF after performing steps (d) and (e), then
perform step (e) again.
GO
15
(a)
READ OUTPUT DTC (DTC P0171, P0172, P0174 AND/OR P0175 ARE OUTPUT
AGAIN)
Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
Display (DTC Output)
Proceed to
DTC P0171, P0172, P0174 and/or P0175 are not output again
A
DTC P0171, P0172, P0174 and/or P0175 are output again
B
B
REPLACE ECM (See page 10-24 ) AND PERFORM CONFIRMATION DRIVING PATTERN
(Refer to step 14)
A
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
698
05-509
DIAGNOSTICS
16
-
SFI SYSTEM (3MZ-FE)
CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
NO
CHECK FOR INTERMITTENT PROBLEMS
(See page 05-370 )
YES
DTC IS CAUSED BY RUNNING OUT OF FUEL (DTCS P0171, P0172, P0174 AND/OR P0175)
17
PERFORM CONFIRMATION DRIVING PATTERN
HINT:
Clear all DTCs prior to performing the confirmation driving pattern (refer to step 14).
GO
18
(a)
READ OUTPUT DTC (DTC P0171, P0172, P0174 AND/OR P0175 ARE OUTPUT
AGAIN)
Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
Display (DTC Output)
Proceed to
DTC P0171, P0172, P0174 and/or P0175 are not output again
A
DTC P0171, P0172, P0174 and/or P0175 are output again
B
B
Go to step 22
A
19
REPLACE AIR FUEL RATIO SENSOR
GO
20
PERFORM CONFIRMATION DRIVING PATTERN
GO
21
(a)
READ OUTPUT DTC (DTC P0171, P0172, P0174 AND/OR P0175 ARE OUTPUT
AGAIN)
Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
Display (DTC Output)
Proceed to
DTC ”P0171, P0172, P0174 and/or P0175” are output again
A
DTC ”P0171, P0172, P0174 and/or P0175” are not output again
B
B
REPLACE ECM (See page 10-24 ) AND PERFORM CONFIRMATION DRIVING PATTER
(Refer to step 14)
A
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
699
05-510
DIAGNOSTICS
22
-
SFI SYSTEM (3MZ-FE)
CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
NO
CHECK FOR INTERMITTENT PROBLEMS
(See page 05-370 )
YES
DTC IS CAUSED BY RUNNING OUT OF FUEL (DTCS P0171, P0172, P0174 AND/OR P0175)
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
Author:
Date:
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