DTC P011B Engine Coolant Temperature/Intake Air Temperature Correlation: Description

The engine has two temperature sensors, an engine coolant temperature sensor and an intake air temperature sensor, to detect the temperature while the engine is operating. A thermistor, whose resistance value varies according to the temperature, is built into each sensor. When the temperature is low, the resistance of the thermistor is high. When the temperature is high, the resistance is low. 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 DETECTION CONDITION CHART

DTC No.	DTC Detection Condition	Trouble Area
P011B	All of the following conditions are met: (2 trip detection logic) Battery voltage 10 5 V or more hours or more elapsed since engine was stopped on previous trip 35.2 seconds after cold engine is started Minimum intake air temperature after engine is started more than -10°C (14°F) Average engine coolant temperature before engine is started more than -10°C (14°F) Difference between readings of engine coolant temperature and intake air temperature is greater than 20°C (68°F)	IAT sensor (built into MAF meter) ECT sensor ECM

Fig 1: Engine Coolant Temperature And Intake Air Temperature Graph

HINT:

Waiting is required to prevent the temperature of the engine from affecting the readings. If the engine has been operated recently, it will not be 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 sensor and intake air temperature sensor are very similar. When the vehicle has been parked for less than 7 hours, differences in the readings may exist, this does not necessarily indicate a fault.