DTC P011B: Engine Coolant Temperature / Intake Air Temperature Correlation [10/2013 - ]: Description

The engine has two temperature sensors, an engine coolant temperature sensor and an intake air temperature sensor, to detect temperature while the engine is operating. A thermistor, whose resistance value varies according to the temperature, is built into each sensor. When the temperature becomes low, the resistance of the thermistor increases. When the temperature becomes high, the resistance drops. These variations in resistance are transmitted to the ECM as voltage changes. Based on these temperature signals output from the sensors, the ECM determines the fuel injection duration and the ignition timing to control the engine.

DTC No.	DTC Detection Condition	Trouble Area
P011B	All of the following conditions are met (2 trip detection logic): The auxiliary battery voltage is 10.5 V or higher. 7 hours or more have elapsed since the engine stopped on the previous trip. 15 seconds or more after a cold engine start. Either of the following conditions is met: The intake air temperature after the engine starts is -10°C (14°F) or higher. The engine coolant temperature before the engine starts is -10°C (14°F) or higher. The difference between the readings of the engine coolant temperature and intake air temperature is higher than 25°C (45°F).	Intake air temperature sensor (built into mass air flow meter sub-assembly) Engine coolant temperature sensor ECM

Fig 1: Identifying Difference Between Engine Coolant Temperature And Air Intake Temperature Graph

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

Waiting is required to prevent the temperature of the engine from affecting the readings. If the engine has been operated recently, it is not possible to accurately compare the readings.

For diagnosis, in order to duplicate the detection conditions of the DTC, it is necessary to park the vehicle for 7 hours. Parking the vehicle for 7 hours ensures that the actual temperature of the engine coolant temperature and intake air temperature are very similar. When the vehicle has been parked for less than 7 hours, differences in the readings may exist, but this does not necessarily indicate a fault.