2AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEMES–101
ES
TYPICAL MALFUNCTION THRESHOLDS
WIRING DIAGRAM
Refer to DTC P0100 (see page ES-88).
CONFIRMATION DRIVING PATTERN
HINT:
Performing this confirmation pattern will activate the mass air flow performance monitor.
1. Connect the intelligent tester to the DLC3.
2. Turn the ignition switch ON.
3. Turn the tester ON.
4. Clear DTCs (see page ES-35).
5. Start the engine, and warm it up until the engine coolant temperature reaches 70
C (158F) or higher.
6. Drive the vehicle at approximately 100 km/h (62 mph) for 20 seconds or more.
7. On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO /
PENDING CODES and check if any DTCs (any pending DTCs) are set.
Engine coolant temperature 70C (158F) or more
IAT sensor circuit OK
ECT sensor circuit OK
CKP sensor circuit OK
TP sensor circuit OK
Canister pressure sensor circuit OK
EVAP leak detection pump OK
EVAP vent valve OK
Both of following conditions 1 and 2 met -
1. Averaged engine load value ratio Less than 0.85, or more than 1.15 (varies with estimated engine load)
2. Averaged air-fuel ratio Less than -20 %, or more than 20 %
A112632E02
ES–1122AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
ES
DESCRIPTION
A thermistor, whose resistance value varies according to the ECT, is built into the Engine Coolant
Temperature (ECT) sensor.
The structure of the sensor and its connection to the ECM are the same as those of the Intake Air
Temperature (IAT) sensor.
HINT:
When any of DTCs P0115, P0117 and P0118 are set, the ECM enters fail-safe mode. During fail-safe
mode, the ECT is estimated to be 80
C (176F) by the ECM. Fail-safe mode continues until a pass
condition is detected.
HINT:
When any of these DTCs are set, check the ECT by selecting the following menu items on the intelligent
tester: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / COOLANT TEMP.
MONITOR DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is used to monitor the ECT. The ECT sensor has a
thermistor with a resistance that varies according to the temperature of the engine coolant. When the
coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the
resistance drops. These variations in resistance are reflected in the output voltage from the sensor. The
ECM monitors the sensor voltage and uses this value to calculate the ECT. When the sensor output
voltage deviates from the normal operating range, the ECM interprets this as a fault in the ECT sensor
and sets a DTC.
Example:
If the sensor output voltage is more than 4.91 V for 0.5 seconds or more, the ECM determines that there
is an open in the ECT sensor circuit, and sets DTC P0118. Conversely, if the voltage output is less than
0.14 V for 0.5 seconds or more, the ECM determines that there is a short in the sensor circuit, and sets
DTC P0117.
If the malfunction is not repaired successfully, a DTC is set 0.5 seconds after the engine is next started.
DTC P0115Engine Coolant Temperature Circuit Malfunc-
tion
DTC P0117 Engine Coolant Temperature Circuit Low Input
DTC P0118 Engine Coolant Temperature Circuit High Input
DTC No. DTC Detection Conditions Trouble Areas
P0115Open or short in ECT sensor circuit for 0.5 seconds (1 trip
detection logic)• Open or short in ECT sensor circuit
• ECT sensor
•ECM
P0117Short in ECT sensor circuit for 0.5 seconds (1 trip detection
logic)• Short in ECT sensor
• ECT sensor
•ECM
P0118Open in ECT sensor circuit for 0.5 seconds (1 trip detection
logic)• Open in ECT sensor circuit
• ECT sensor
•ECM
Temperature Displayed Malfunctions
-40
C (-40F) Open circuit
140
C (284F) or higher Short circuit
