Text in Illustration
(d) Reconnect the engine room junction block assembly connector.
(e) Reinstall the engine room junction block assembly.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE ROOM JUNCTION BLOCK ASSEMBLY - BODY
GROUND)
OK -- REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY
From 08/2009
2GR-FE ENGINE CONTROL: SFI SYSTEM: P0031,P0032,P0051,P0052: Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1
Sensor 1)
P0052 - Oxygen (A/F) Sensor Heater Control 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 time. If the air fuel ratio sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.
The air fuel ratio sensor is the planar type and is integrated with a 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.
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 three way catalytic converter is used. For the most efficient use of the three way catalytic converter, 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 air fuel ratio sensor is the 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.
HINT
- When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio sensor heater in fail-safe
mode. Fail-safe mode continues until the engine switch is turned off.
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