P2255
2GR-FSE 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 the 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 though the alumina, therefore the sensor activation is accelerated.
In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC is used. For the most efficient use of the TWC, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.
*: 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 the No. 1 cylinder.
- Bank 2 refers to the bank that includes the 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
TYPICAL ENABLING CONDITIONS
All:
P2237, P2240:
A/F sensor - Low Admittance P2238 and P2241:
Other:
TYPICAL MALFUNCTION THRESHOLDS
A/F Sensor Open Circuit Between A1A+ and A1A-/A2A+ and A2A- P2237 and P2240:
A/F Sensor Short Circuit Between A1A+ and A1A-/A2A+ and A2A- P2238 and P2241:
A/F Sensor Short Circuit Between A1A+ and GND/A2A+ and GND P2238 and P2241:
A/F Sensor Admittance Low P2238 and P2241:
A/F Sensor Short Circuit Between A1A+ and +B/A2A+ and +B P2239 and P2242:
A/F Sensor Short Circuit Between A1A- and GND/A2A- and GND P2252 and P2255:
A/F Sensor Short Circuit Between A1A- and +B/A2A- and +B P2253 and P2256:
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 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 Techstream.
1. Put the engine in inspection mode Inspection Mode Procedure.
2. Connect the Techstream to the DLC3.
3. Turn the Techstream on.
4. Warm up the engine.
5. On the Techstream, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
6. 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 injection volume).
7. 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 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 and ECT / Active Test / Control the Injection Volume for A/F Sensor / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and 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) P0031
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.
2. INSPECT INTEGRATION NO.1 RELAY (A/F RELAY) P0031
NG -- REPLACE INTEGRATION NO.1 RELAY
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) P0031
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. REPLACE AIR FUEL RATIO SENSOR
NEXT -- Continue to next step.
5. CHECK WHETHER DTC OUTPUT RECURS
(a) Clear the DTCs DTC Check / Clear.
(b) Put the engine in inspection mode Inspection Mode Procedure.
(c) Connect the Techstream to the DLC3.
(d) Turn the Techstream on.
(e) Allow the engine to idle for 5 minutes or more.
(f) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
(g) Read pending DTCs.
Result:
B -- REPLACE ECM Removal
A -- END