ECD SYSTEM, Diagnostic DTC:22

DTC Code	DTC Name
22	Water Temperature Sensor Circuit Malfunction

DESCRIPTION

The engine coolant temperature sensor senses the coolant temperature. A thermistor built into the sensor changes the resistance value according to the coolant temperature. The lower the coolant temperature, the greater the thermistor resistance value, and the higher the coolant temperature, the lower the thermistor resistance value (See Fig. 1).

The water temperature sensor is connected to the ECM (See below). The 5 V power source voltage in the ECM is applied to the engine coolant temperature sensor from the terminal THW via a resistor R. That is, resistor R and the water temperature sensor are connected in series. When the resistance value of the engine coolant temperature sensor changes in accordance with changes in the coolant temperature, the potential at the terminal THW also changes. Based on this signal, the ECM increases the fuel injection volume to improve driveability during cold engine operation.

DTC No.	DTC Detecting Condition	Trouble Area
22	Open or short in engine coolant temp. sensor circuit for 0.5 sec. or more	Open or short in water temp. sensor circuit Engine coolant temp sensor ECM

Tech Tips

After confirming DTC No. 22, use the intelligent tester to confirm the engine coolant temperature from the CURRENT DATA.

Temperature displayed	Malfunction
-40°C (-40°F)	Open circuit
140°C (284°F) or more	Short circuit

WIRING DIAGRAM

INSPECTION PROCEDURE

Tech Tips

If DTC Nos. 22, 24 and 39 are output simultaneously, E2 (sensor ground) may be open.
Read freeze frame data using intelligent tester. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
When not using the intelligent tester go to step 6.

PROCEDURE

READ VALUE OF INTELLIGENT TESTER (WATER TEMP.)

Connect the intelligent tester to the DLC3.
Turn the ignition switch ON and push the intelligent tester main switch ON.

Read the temperature value on the intelligent tester.

Temp.
Same as actual water temperature.

Result

A	B	OK
-40°C (-40°F)	140°C (248°F) or more	Same as actual water temperature

Tech Tips

If there is open circuit, intelligent tester indicates -40°C (-40°F) (A).
If there is short circuit, intelligent tester indicates 140°C (284°F) or more (B).

CHECK ECM (CHECK FOR SHORT) Click here

CHECK FOR INTERMITTENT PROBLEMS Click here

CHECK WIRE HARNESS (CHECK FOR OPEN)
1. Text in Illustration
  
  *1 Water Temp. Sensor
  
  Disconnect the engine coolant temperature sensor connector.
2. Connect the sensor wire harness terminals together.
3. Turn the ignition switch ON.
4. Read the temperature value on the intelligent tester.
  
  Temperature value
  
  140°C (284°F) or more
5. Confirm good connection at sensor.
OK
REPLACE ENGINE COOLANT TEMPERATURE SENSOR

NG
CHECK ECM (CHECK FOR OPEN)
1. Connect between terminals THW and E2 of the ECM (E8) connector.
  
  Tech Tips
  
  The engine coolant temperature sensor connector is disconnected. Before checking, do a visual and contact pressure check for the ECM connector Click here.
2. Turn the ignition switch ON.
3. Read the temperature value on the intelligent tester.
  
  Temperature value
  
  140°C (284°F) or more
4. Confirm good connection at sensor.
OK
REPAIR OR REPLACE HARNESS AND CONNECTOR

NG

REPLACE ECM
CHECK ECM (CHECK FOR SHORT)
1. Disconnect the water temperature sensor connector.
2. Turn the ignition switch ON.
3. Read the temperature value on the intelligent tester.
  
  Temperature value
  
  -40°C (-40°F)
OK
REPLACE ENGINE COOLANT TEMPERATURE SENSOR

NG
CHECK ECM (CHECK FOR SHORT)
1. Text in Illustration
  
  *1 E8 Connector
  
  Disconnect the ECM (E8) connector.
  
  Tech Tips
  
  The engine coolant temperature sensor connector is disconnected.
2. Read the temperature value on the intelligent tester.
  
  Temperature value
  
  -40°C (-40°F)
OK
REPAIR OR REPLACE HARNESS AND CONNECTOR

NG

CHECK AND REPLACE ECM Click here

Text in Illustration
*1	Water Temp. Sensor

Temperature value
140°C (284°F) or more

Temperature value
140°C (284°F) or more

Temperature value
-40°C (-40°F)

Text in Illustration
*1	E8 Connector

Temperature value
-40°C (-40°F)

CHECK ECM (CHECK VOLTAGE)

Turn the ignition switch ON.

Check the voltage between terminals of the ECM connector as shown in the table and illustration.

Voltage

Engine coolant Temp.

°C (°F)

Terminal

(Positive terminal ←→ Negative terminal)

Voltage

20 (68)

(Engine is cool)

THW (E8-14) ←→ E2 (E8-20)

0.2 - 3.8 V

80 (176)

(Engine is hot)

THW (E8-14) ←→ E2 (E8-20)

0.1 - 1.5 V

CHECK FOR INTERMITTENT PROBLEMS Click here

INSPECT ENGINE COOLANT TEMPERATURE SENSOR (CHECK RESISTANCE)

Disconnect the engine coolant temp. sensor connector.
Remove the engine coolant temp. sensor.

Measure resistance between terminals.

Resistance
Within acceptable zone on the chart below

Engine coolant temp.

°C (°F)

Resistance

20 (68)

2 - 3 kΩ

80 (176)

0.2 - 0.4 kΩ

REPLACE ENGINE COOLANT TEMPERATURE SENSOR

CHECK WIRE HARNESS (ECM - WATER TEMPERATURE SENSOR)

Disconnect the engine coolant temp. sensor connector.
Disconnect the ECM (E8) connector.

Check the continuity between terminals of engine coolant temp. sensor and ECM connectors as shown in the illustration and table.

Continuity (Check for open)

Terminal

(Engine coolant temp. sensor ←→ ECM)

Standard

2 ←→ THW (E8-14)

Continuity

1 ←→ E2 (E8-20)

Continuity (Check for short)

Terminal

(ECM ←→ ECM(Ground))

Standard

THW (E8-14) ←→ E1 (E7-22)

No continuity

REPAIR OR REPLACE HARNESS AND CONNECTOR

CHECK AND REPLACE ECM Click here