P2253
2AZ-FXE ENGINE CONTROL SYSTEM: SFI SYSTEM: P2237-P2239,P2252,P2253: Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 1 Sensor 1)
DTC P2237 - Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 1 Sensor 1)
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 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)
CAUTION / NOTICE / HINT
DESCRIPTION
The A/F sensor generates a voltage* that corresponds to the actual air-fuel ratio. This sensor voltage is used to provide the ECM (included in the hybrid vehicle control ECU) 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 duration. If the A/F sensor malfunctions, the ECM is unable to control the air-fuel ratio accurately.
The A/F sensor is a planar type and is integrated with the heater, that 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 air-fuel ratio 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 uses a current output element, the current is converted into a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.
HINT:
- When either of these DTCs is set, check the A/F sensor output voltage by selecting the following menu items on the Techstream: Powertrain / Engine / Data List / A/F Control System / AFS B1 S1.
- Short-term fuel trim values can also be read using the Techstream.
- The ECM regulates the voltages at the A1A+ and A1A- terminals of the ECM to a constant level. Therefore, the A/F sensor output voltage cannot be confirmed without using the Techstream.
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 (included in the hybrid vehicle control ECU) determines that there is an open or short in the A/F sensor circuit.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
P2237 (Open circuit between AF+ and AF-):
P2238 (Open circuit between AF+ and GND
Other:
TYPICAL MALFUNCTION THRESHOLDS
P2237 (Open circuit between AF+ and AF-):
P2238 (A/F sensor low admittance):
P2238 (Short circuit between AF+ and GND):
P2238 (Short circuit between AF+ and AF-):
P2239 (Short circuit between AF+ and +B):
P2252 (Short circuit between AF- and GND):
P2253 (Short circuit between AF- and +B):
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
- Although the DTC titles say 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.
HINT: 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.
(a) Connect the Techstream to the DLC3.
(b) Put the engine in inspection mode Component Tests and General Diagnostics.
(c) Turn the tester on.
(d) Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
(e) On the tester, select the following menu items: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.
(f) Perform the Control the Injection Volume for A/F sensor operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
(g) Monitor the output voltages of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2) 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%.
- The sensors react in accordance with increases and decreases in the fuel injection volume.
Standard:
NOTICE: The A/F sensor has an output delay of a few seconds and the 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, select the following menu items on the tester: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS B1 S1 and O2S B1 S2 then press the graph button on the Data List view.
HINT: Read freeze frame data using the Techstream. The ECM (included in the hybrid vehicle control ECU) records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, 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.
PROCEDURE
1. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) P0031
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.
2. INSPECT INTEGRATION RELAY (EFI RELAY) P0031
NG -- REPLACE INTEGRATION RELAY (EFI MAIN RELAY)
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (A/F SENSOR - HYBRID VEHICLE CONTROL ECU) P2195
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. REPLACE AIR FUEL RATIO SENSOR
(a) Replace the air fuel ratio sensor Removal.
NEXT -- Continue to next step.
5. CHECK WHETHER DTC OUTPUT RECURS
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG) and turn the tester on.
(c) Clear the DTCs DTC Check / Clear.
(d) Put the engine in inspection mode Component Tests and General Diagnostics.
(e) Allow the engine to idle for 5 minutes or more.
(f) Select the following menu items: Powertrain / Engine / Trouble Code / Pending.
(g) Read the pending DTCs.
Result:
B -- REPLACE HYBRID VEHICLE CONTROL ECU
A -- END