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P2256





2GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P2237-P2239,P2240-P2242,P2252,P2253,P2255,P2256: Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 1 Sensor 1)


DESCRIPTION

HINT
- Although the DTC titles include oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
- Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
The A/F sensor generates voltage* that corresponds to the actual air-fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air-fuel ratio. The ECM determines the deviation from the stoichiometric air-fuel ratio level, and regulates the fuel injection time. If the A/F sensor malfunctions, the ECM is unable to control the air-fuel ratio accurately.

The A/F sensor is the planar type and is integrated with the heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore the sensor activation is accelerated.

A three-way catalytic converter (TWC) is used in order to convert the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) into less harmful substances. To allow the TWC to function effectively, it is necessary to keep the air-fuel ratio of the engine near the stoichiometric air-fuel ratio.

*: Value changes inside the ECM. Since the A/F sensor is the current output element, a current is converted to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.









HINT
- DTCs P2237, P2238, P2239, P2252 and P2253 indicate malfunctions related to the bank 1 A/F sensor circuit.
- DTCs P2240, P2241, P2242, P2255 and P2256 indicate malfunctions related to the bank 2 A/F sensor circuit.
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that includes cylinder No. 2.
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





TYPICAL ENABLING CONDITIONS





P2237 and P2240 (Air fuel ratio sensor open circuit between A1A+ and A1A-/A2A+ and A2A-):

P2237 and P2240 (Air fuel ratio sensor open circuit between A1A+ and A1A-/A2A+ and A2A-)::





P2238 and P2241 (Open circuit between A1A+ and A1A-/A2A+ and A2A-):

P2238 and P2241 (Open circuit between A1A+ and A1A-/A2A+ and A2A-)::





Others:

Others::





TYPICAL MALFUNCTION THRESHOLDS

P2237 and P2240 (Open circuit between A1A+ and A1A-/A2A+ and A2A-):

P2237 and P2240 (Open circuit between A1A+ and A1A-/A2A+ and A2A-)::





P2238 and P2241 (Low admittance)

P2238 and P2241 (Low admittance):





P2238 and P2241 (Short circuit between A1A+ and GND/A2A+ and GND):

P2238 and P2241 (Short circuit between A1A+ and GND/A2A+ and GND)::





P2238 and P2241 (Short circuit between A1A+ and A1A-/A2A+ and A2A-):

P2238 and P2241 (Short circuit between A1A+ and A1A-/A2A+ and A2A-)::





P2239 and P2242 (Short circuit between A1A+ and +B/A2A- and +B):

P2239 and P2242 (Short circuit between A1A+ and +B/A2A- and +B)::





P2252 and P2255 (Short circuit between A1A- and GND/A2A- and GND):

P2252 and P2255 (Short circuit between A1A- and GND/A2A- and GND)::





P2253 and P2256 (Short circuit between A1A- and +B/A2A- and +B):

P2253 and P2256 (Short circuit between A1A- and +B/A2A- and +B)::





COMPONENT OPERATING RANGE





CONFIRMATION DRIVING PATTERN





- Connect the Techstream to the DLC3.

- Turn the engine switch on (IG) and turn the Techstream on.

- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) DTC Check / Clear.

- Turn the engine switch off and wait for 30 seconds.

- Turn the engine switch on (IG) and turn the Techstream on [A].

- Start the engine and wait 2 minutes.

- Enter the following menus: Powertrain / Engine / Trouble Codes / Pending.

- Read the pending DTC [B].

- If a pending DTC is output, the system is malfunctioning.

HINT
If a pending DTC is not output, perform the following procedure.

- Enter the following menus: Powertrain / Engine / Utility / All Readiness.

- Input the DTC: P2237, P2238, P2239, P2240, P2241, P2242, P2252, P2253, P2255 or P2256.

- Check the DTC judgment result.





HINT
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows NORMAL, the system is normal.
- If the judgment result shows INCOMPLETE or UNKNOWN, idle the engine for 3 minutes.
- Enter the following menus: Powertrain / Engine / Utility / All Readiness.

- Check the judgment result [C].

HINT
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows NORMAL, the system is normal.
- If the test result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs DTC Check / Clear.

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 P2195 P2195.

INSPECTION PROCEDURE

HINT
Techstream only:

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F sensor operation 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 Techstream.

- Connect the Techstream to the DLC3.

- Start the engine and turn the Techstream on.

- Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

- On the Techstream, enter the following menus: 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 output voltages of the A/F and HO2 sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

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.






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.





- Following the Control the Injection Volume for A/F sensor procedure enables technicians to check and graph the output voltages of both the A/F and HO2 sensors.

- To display the graph, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1S1 or AFS Voltage B2S1 and O2S B1S2 or O2S B2S2 then press the graph button on the Data List view.

HINT
- 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 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 Freeze Frame Data.
PROCEDURE

1. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

(a) Disconnect the B3 or B4 A/F sensor connector.





(b) Measure the resistance according to the value(s) in the table below.

Standard resistance (Bank 1 sensor 1):





Standard resistance (Bank 2 sensor 1):





(c) Reconnect the A/F sensor connector.

NG -- REPLACE AIR FUEL RATIO SENSOR Removal
OK -- Continue to next step.

2. INSPECT A/F FUSE

(a) Remove the A/F fuse from the engine room junction block.





(b) Measure the A/F fuse resistance.

Standard resistance:

Below 1 Ohms

(c) Reinstall the A/F fuse.

NG -- REPLACE A/F FUSE
OK -- Continue to next step.

3. INSPECT ENGINE ROOM JUNCTION BLOCK (A/F RELAY)

(a) Remove the engine room junction block from the engine room relay block.





(b) Inspect the A/F relay.

(1) Measure the A/F relay resistance.

Standard resistance:





(c) Reinstall the engine room junction block.

NG -- REPLACE ENGINE ROOM JUNCTION BLOCK
OK -- Continue to next step.

4. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)

(a) Disconnect the B3 and B4 A/F sensor connectors.





(b) Turn the engine switch on (IG).

(c) Measure the voltage according to the value(s) in the table below.

Standard voltage:





(d) Turn the engine switch off.

(e) Disconnect the B12 ECM connector.

(f) Measure the resistance according to the value(s) in the table below.

Standard resistance (Check for open):





Standard resistance (Check for short):





(g) Reconnect the ECM connector.

(h) Reconnect the A/F sensor connectors.





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

5. REPLACE AIR FUEL RATIO SENSOR

(a) Replace air fuel ratio sensor Components.

NEXT -- Continue to next step.

6. PERFORM CONFIRMATION DRIVING PATTERN

NEXT -- Continue to next step.

7. CHECK WHETHER DTC OUTPUT RECURS

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Select the following menu items: Powertrain / Engine / Trouble Codes / Pending.

(e) Read the pending DTCs.

Result:





B -- REPLACE ECM Removal

A -- END
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