P011B
2UZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P011B: Engine Coolant Temperature / Intake Air Temperature Correlation
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.
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.
MONITOR DESCRIPTION
The ECM monitors the difference between the Engine Coolant Temperature (ECT) and the Intake Air Temperature (IAT) when the engine is started cold to detect the engine temperature conditions accurately. The monitor runs when the engine started cold after 7 hours or more have elapsed since the engine was stopped (ignition switch turned off) on the previous trip. If the difference between the ECT and the IAT on a cold start exceeds 20°C (68°F), the ECM interprets this as a malfunction in the ECT sensor circuit and IAT sensor circuit, and stores the DTC.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
INSPECTION PROCEDURE
PROCEDURE
1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO P011B)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(e) Read DTCs.
Result:
HINT: If any DTCs other than P011B are output, troubleshoot those DTCs first.
B -- GO TO DTC CHART
A -- Continue to next step.
2. READ VALUE USING TECHSTREAM (INTAKE AIR TEMPERATURE)
(a) Leave the vehicle for 7 hours or more.
HINT: It is necessary leave the vehicle for 7 hours or more to allow conditions similar to the DTC detection conditions.
(b) Connect the Techstream to the DLC3.
(c) Turn the ignition switch to ON.
(d) Turn the Techstream on.
(e) Enter the following menus: Powertrain / Engine and ECT / All Data / Intake Air.
(f) Read the value displayed on the Techstream.
OK:
Difference between the intake air temperature and the actual outside air temperature is within 10°C (50°F).
HINT: Temperature readings on the vehicle outside temperature gauge (if equipped) are not suitable for comparing to the IAT reading. The outside temperature gauge has a significant delay built in to prevent temperature swings from being displayed on its display. Use an accurate thermometer to determine the outside air temperature.
NG -- REPLACE MASS AIR FLOW METER
OK -- Continue to next step.
3. READ VALUE USING TECHSTREAM (COOLANT TEMPERATURE)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / All Data / Coolant Temp.
(e) Read the value displayed on the Techstream.
OK:
The difference between the coolant temperature and the actual outside air temperature is within 10°C (50°F).
HINT: If the result is not as specified, check that there are heat sources such as a block heater in the engine compartment.
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- REPLACE ECM