Sfi System - P2256

Brand:

Toyota

Model Name:

4Runner GRN210 215 UZN210 215

Manual:

Repair Manual

Section:

2Uz-Fe Engine Control System

Title:

Sfi System

  1. Description

  2. Monitor description

  3. Monitor strategy

  4. Typical enabling conditions

  5. Typical malfunction thresholds

  6. Wiring diagram

  7. Inspection procedure

  8. Inspect air fuel ratio sensor (heater resistance)

  9. Inspect a/f relay

  10. Check harness and connector (a/f sensor - ecm)

DTC P2238 Oxygen (A/F) Sensor Pumping Current Circuit Low (Bank 1 Sensor 1)

DTC P2239 Oxygen (A/F) Sensor Pumping Current Circuit High (Bank 1 Sensor 1)

DTC P2241 Oxygen (A/F) Sensor Pumping Current Circuit Low (Bank 2 Sensor 1)

DTC P2242 Oxygen (A/F) Sensor Pumping Current Circuit High (Bank 2 Sensor 1)

DTC P2252 Oxygen (A/F) Sensor Reference Ground Circuit Low (Bank 1 Sensor 1)

DTC P2253 Oxygen (A/F) Sensor Reference Ground Circuit High (Bank 1 Sensor 1)

DTC P2255 Oxygen (A/F) Sensor Reference Ground Circuit Low (Bank 2 Sensor 1)

DTC P2256 Oxygen (A/F) Sensor Reference Ground Circuit High (Bank 2 Sensor 1)


​

DESCRIPTION

HINT:
  1. Although the DTC titles refer to the "oxygen sensor", these DTCs relate to the Air Fuel Ratio (A/F) sensor.
  2. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and is located near the engine assembly.
Refer to DTC P2195 (Click here).

DTC No.
DTC Detection Condition
Trouble Area
P2238
P2241
  1. Case 1:
    Condition (a) or (b) continues for 5.0 seconds or more
    (1 trip detection logic):
    (a) AF+ voltage 0.5 V or less
    (b) (AF+) - (AF-) = 0.1 V or less
  2. Case 2:
    A/F sensor admittance: Less than 0.0221/Ω
    (2 trip detection logic)
  1. Open or short in Air Fuel Ratio (A/F) sensor (bank 1, 2 sensor 1) circuit
  2. Air Fuel Ratio (A/F) sensor (bank 1, 2 sensor 1)
  3. Air Fuel Ratio (A/F) sensor heater (bank 1, 2 sensor 1)
  4. A/F relay
  5. A/F sensor heater and relay circuits
  6. ECM
P2239
P2242
AF+ voltage more than 4.5 V for 5.0 seconds or more
(2 trip detection logic)
  1. Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
  2. A/F sensor (bank 1, 2 sensor 1)
  3. A/F sensor heater (bank 1, 2 sensor 1)
  4. A/F relay
  5. A/F sensor heater and relay circuits
  6. ECM
P2252
P2255
AF- voltage 0.5 V or less for 5.0 seconds or more
(2 trip detection logic)
  1. Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
  2. A/F sensor (bank 1, 2 sensor 1)
  3. A/F sensor heater (bank 1, 2 sensor 1)
  4. A/F relay
  5. A/F sensor heater and relay circuits
  6. ECM
P2253
P2256
AF- voltage more than 4.5 V for 5.0 seconds or more
(2 trip detection logic)
  1. Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
  2. A/F sensor (bank 1, 2 sensor 1)
  3. A/F sensor heater (bank 1, 2 sensor 1)
  4. A/F relay
  5. A/F sensor heater and relay circuits
  6. ECM
HINT:
  1. DTCs P2238, P2239, P2252 and P2253 indicate malfunctions related to bank 1 A/F sensor circuit.
  2. DTCs P2241, P2242, P2255 and P2256 indicate malfunctions related to bank 2 A/F sensor circuit.
  3. Bank 1 refers to the bank that includes No. 1 cylinder.
  4. Bank 2 refers to the bank that includes No. 2 cylinder.

MONITOR DESCRIPTION

The Air Fuel Ratio (A/F) sensor varies its output voltage in proportion to the air fuel ratio. If the A/F sensor impedance (alternating current resistance) or output voltage deviates greatly from the standard range, the ECM determines that there is an open or short malfunction in the A/F sensor circuit.

MONITOR STRATEGY


Related DTCs
P2238: A/F sensor (Bank 1) open circuit between AF+ and AF-
P2238: A/F sensor (Bank 1) short circuit between AF+ and AF-
P2238: A/F sensor (Bank 1) short circuit between AF+ and GND
P2239: A/F sensor (Bank 1) short circuit between AF+ and +B
P2241: A/F sensor (Bank 2) open circuit between AF+ and AF-
P2241: A/F sensor (Bank 2) short circuit between AF+ and AF-
P2241: A/F sensor (Bank 2) short circuit between AF+ and GND
P2242: A/F sensor (Bank 2) short circuit between AF+ and +B
P2252: A/F sensor (Bank 1) short circuit between AF- and GND
P2253: A/F sensor (Bank 1) short circuit between AF- and +B
P2255: A/F sensor (Bank 2) short circuit between AF- and GND
P2256: A/F sensor (Bank 2) short circuit between AF- and +B
Required Sensors/Components
A/F sensor
Frequency of Operation
Once per driving cycle
Duration
10 seconds: A/F sensor open circuit between AF+ and AF-
5 seconds: Others
MIL Operation
2 driving cycles: A/F sensor open circuit between AF+ and AF-
Immediate: Others
Sequence of Operation
None

TYPICAL ENABLING CONDITIONS


Monitor runs whenever following DTCs not present
None

P2238 and P2241 (open circuit between AF+ and AF-):
Duration while all of following conditions met
-
AF+ terminal voltage
0.5 to 4.5 V
AF- terminal voltage
0.5 to 4.5 V
Difference between AF+ and AF- terminal voltages
0.1 to 0.8 V
ECT
More than 0°C (32°F): closed-loop fuel control enable temperature
Engine
Running
Time after fuel - cut OFF
5 seconds or more
Fuel-cut
OFF
A/F sensor heater
ON
Time after ignition switch OFF to ON
5 seconds or more
Battery voltage
11 V or more
Ignition switch
ON

Others:
Battery voltage
11 V or more
Ignition switch
ON
Time after ignition switch is OFF to ON
5 seconds or more

TYPICAL MALFUNCTION THRESHOLDS


P2238 and P2241 (Open circuit between AF+ and AF-):
A/F sensor admittance
Below 0.022 1/Ω

P2238 and P2241 (Short circuit between AF+ and GND):
AF+ terminal voltage
0.5 V or less

P2238 and P2241 (Short circuit between AF+ and AF-):
Difference between AF+ and AF- terminal voltages
0.1 V or less

P2239 and P2242 (Short circuit between AF+ and +B):
AF+ terminal voltage
More than 4.5 V

P2252 and P2255 (Short circuit between AF- and GND):
AF- terminal voltage
0.5 V or less

P2253 and P2256 (Short circuit between AF- and +B):
AF- terminal voltage
More than 4.5 V

WIRING DIAGRAM

Refer to DTC P2195 (Click here).

INSPECTION PROCEDURE

HINT:
Intelligent tester only:
Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE TEST. The A/F CONTROL 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 A/F CONTROL operation using the intelligent tester.
  1. Connect the intelligent tester to the DLC3 with CAN VIM.
  2. Start the engine and turn the tester ON.
  3. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
  4. On the tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
  5. Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
  6. Monitor the output voltages of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.
    HINT:
    1. The A/F CONTROL operation lowers the fuel injection volume by 12.5 % or increases the injection volume by 25 %.
    1. Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

    Standard voltage:

    Tester Display
    (Sensor)
    		Injection Volume
    		Status
    		Voltage
    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 output delay of approximately 20 seconds.

    Case
    		A/F Sensor (Sensor 1)
    Output Voltage
    		HO2 Sensor (Sensor 2)
    Output Voltage
    		Main Suspected Trouble Areas
    1
    		Injection Volume
    +25 %
    -12.5 %
    		A/F sensor 4Runner
    		Injection Volume
    +25 %
    -12.5 %
    		A/F sensor 4Runner
    		-
    Output Voltage
    More than 3.35 V
    Less than 3.0 V
    		A/F sensor 4Runner
    		Output Voltage
    More than 0.55 V
    Less than 0.4 V
    		A/F sensor 4Runner
    2
    		Injection Volume
    +25 %
    -12.5 %
    		A/F sensor 4Runner
    		Injection Volume
    +25 %
    -12.5 %
    		A/F sensor 4Runner
    1. A/F sensor
    2. A/F sensor heater
    3. A/F sensor circuit
    Output Voltage
    Almost
    no reaction
    		HO2 sensor 4Runner
    		Output Voltage
    More than 0.55 V
    Less than 0.4 V
    		HO2 sensor 4Runner
    3
    		Injection Volume
    +25 %
    -12.5 %
    		HO2 sensor 4Runner
    		Injection Volume
    +25 %
    -12.5 %
    		HO2 sensor 4Runner
    1. HO2 sensor
    2. HO2 sensor heater
    3. HO2 sensor circuit
    Output Voltage
    More than 3.35 V
    Less than 3.0 V
    		Fuel injector 4Runner
    		Output Voltage
    Almost
    no reaction
    		Fuel injector 4Runner
    4
    		Injection volume
    +25 %
    -12.5 %
    		Fuel injector 4Runner
    		Injection Volume
    +25 %
    -12.5 %
    		Fuel injector 4Runner
    1. Fuel injector
    2. Fuel pressure
    3. Gas leakage from exhaust system
      (Air fuel ratio extremely lean or rich)
    Output Voltage
    Almost
    no reaction
    		Following the A/F CONTROL procedure enables technicians to check and graph the output voltages of both the A/F and HO2 sensors. 4Runner
    		Output Voltage
    Almost
    no reaction
    		Following the A/F CONTROL procedure enables technicians to check and graph the output voltages of both the A/F and HO2 sensors. 4Runner
  1. Following the A/F CONTROL procedure enables technicians to check and graph the output voltages of both the A/F and HO2 sensors.
  2. To display the graph, enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2. Then press the YES button and ENTER button, followed by the F4 button.
    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.
1.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
  1. Disconnect the A12 or A13 Air Fuel Ratio (A/F) sensor connector. 4Runner

  2. Disconnect the A12 or A13 Air Fuel Ratio (A/F) sensor connector.

  1. Measure the resistance of the A/F sensor connector.

    Standard resistance:
    Tester Connection
    		Specified Condition
    HT (1) - +B (2)
    		1.8 to 3.4 Ω at 20°C (68°F)
    HT (1) - AF- (4)
    		10 kΩ or higher

  1. Reconnect the A/F sensor connector.



NGnext
REPLACE AIR FUEL RATIO SENSOR
OK
next down

2.INSPECT A/F RELAY
  1. Remove the A/F relay from the engine room relay block. 4Runner

  2. Remove the A/F relay from the engine room relay block.

  1. Measure the resistance of the A/F relay.

    Standard resistance:
    Tester Connection
    		Specified Condition
    3 - 5
    		10 kΩ or higher
    3 - 5
    		Below 1 Ω
    (when battery voltage applied to terminals 1 and 2)

  1. Reinstall the A/F relay.



NGnext
REPLACE A/F RELAY
OK
next down

3.CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
  1. Disconnect the A12 or A13 A/F sensor connector. 4Runner

  2. Disconnect the A12 or A13 A/F sensor connector.

  1. Turn the ignition switch to ON.

  1. Measure the voltage between the +B terminal of the A/F sensor connector and body ground.

    Standard voltage:
    Tester Connections
    		Specified Conditions
    +B (2) - Body ground
    		Between 9 V and 14 V

  1. Turn the ignition switch to OFF.

  1. Disconnect the E5 ECM connector.

  1. Check the resistance.

    Standard resistance (Check for open):
    Tester Connections
    		Specified Conditions
    HT (A12-1) - HA1A (E5-2)
    HT (A13-1) - HA2A (E5-1)
    		Below 1 Ω
    AF+ (A12-3) - A1A+ (E5-22)
    AF+ (A13-3) - A2A+ (E5-23)
    		Below 1 Ω
    AF- (A12-4) - A1A- ((E5-30)
    AF- (A13-4) - A2A- (E5-31)
    		Below 1 Ω
    Standard resistance (Check for short):
    Tester Connections
    		Specified Conditions
    HT (A12-1) or HA1A (E5-2) - Body ground
    HT (A13-1) or HA2A (E5-1) - Body ground
    		10 kΩ or higher
    AF+ (A12-3) or A1A+ (E5-22) - Body ground
    AF+ (A13-3) or A2A+ (E5-23) - Body ground
    		10 kΩ or higher
    AF- (A12-4) or A1A- ((E5-30) - Body ground
    AF- (A13-4) or A2A- (E5-31) - Body ground
    		10 kΩ or higher

    Sfi System - P0335 4Runner



NGnext
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK
next down
REPLACE ECM