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

The engine has two temperature sensors, an Engine Coolant Temperature (ECT) sensor and an Intake Air Temperature (IAT) sensor, to detect the temperature while the engine is in operation. 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 increases. When the temperature is 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 time and the ignition timing to control the engine.

DTC DETECTION CONDITION CHART

DTC No.	DTC Detection Condition	Trouble Area
P011B	All of following conditions met (2 trip detection logic) Battery voltage 10.5 V or more 7 hours or more elapsed from engine stops on previous trip 15 seconds after cold engine starts Minimum Intake Air Temperature (IAT) after engine starts more than -10°C (14°F) Average Engine Coolant Temperature (ECT) before engine starts more than -10°C (14°F) Difference between readings of ECT and IAT greater than 20°C (36°F)	IAT sensor ECT sensor ECM

Fig 1: ECT Sensor And IAT Sensor 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 ECT and IAT 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.