(d) Clear the DTCs See: Powertrain Management/Computers and Control Systems/Testing and Inspection/Reading and Clearing
Diagnostic Trouble Codes/DTC Check / Clear.
(e) Turn the engine switch off.
(f) Turn the engine switch on (IG) and turn the Techstream on.
(g) Start the engine and warm it up.
(h) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
(i) Enter the following menus: Powertrain / Engine / Utility / All Readiness.
(j) Input the DTC: P2237, P2238, P2239, P2240, P2241, P2242, P2252, P2253, P2255 or P2256.
(k) Check the DTC judgment result.
Result:
B -- REPLACE ECM See: Powertrain Management/Computers and Control Systems/Engine Control Module/Service and
Repair/Removal
A -- END
Up to 08/2009
2GR-FE ENGINE CONTROL: SFI SYSTEM: P2237-P2239,P2240-P2242,P2252,P2253,P2255,P2256: Oxygen (A/F) Sensor Pumping
Current Circuit / Open (Bank 1 Sensor 1)
P2256 - Oxygen (A/F) Sensor Reference Ground Circuit High (Bank 2 Sensor 1)
DESCRIPTION
HINT
- Although the DTC titles include oxygen sensor, these DTCs relate to the air fuel ratio sensor.
- Sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.
The air fuel ratio 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 duration. If the air fuel ratio sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.
The air fuel ratio sensor is a planar type with an integrated 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), current flows to 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 is used in order to convert the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) into less
harmful substances. To allow the three-way catalytic converter 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 air fuel ratio sensor uses a current output element, the current is converted to a voltage inside the ECM.
Any measurements taken at the air fuel ratio sensor or ECM connectors will show a constant voltage.
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