Test B3 - Engine Coolant Temperature (ECT) Sensor

Fig 1: ECT Sensor Circuits

CIRCUIT PIN IDENTIFICATION

Circuit	Breakout Box Pin	ECA Pin
2.2L MTX Non-Turbo
ECT	7	2Q
SIGRTN	46, 49	3D
2.2L Except MTX Non-Turbo
ECT	7	2E
SIGRTN	46, 49	2D

NOTE: Enter this test only when a Code 09 is displayed during the QUICK TEST procedure or when directed here from another CIRCUIT TEST. To prevent unnecessary diagnosis, inspect coolant level, oil level, cooling fan, thermostat and airflow to radiator for obstruction prior to electronic testing.

1) Checking System Integrity Visually check all wiring, harnesses, connectors and components for evidence of damage, overheating, shorting or looseness. If a fault is found, repair as necessary. If no faults are found, go to next step.

2) Checking ECT Voltage Ensure engine is at operating emperature. With key off, install breakout box. Turn ignition on. Measure voltage between ECT and SIGRTN test pins. Compare voltage to specifications shown in ECT SENSOR SPECIFICATIONS . If voltage is within specification, ECT circuit is okay. Fault is in another circuit or ECA. If voltage is not within specification, go to step 3.

3) Checking ECT Resistance Ensure engine is at operating temperature. With key off, install breakout box. Measure resistance between ECT and SIGRTN test pins. Compare resistance to specifications shown in ECT SENSOR SPECIFICATIONS . If resistance is within specification, go to step 4. If resistance is not to specification, go to step 5.

ECT & VAT SENSORS

Temperature: °F (°C)

Voltage: Volts

⁽¹⁾ Resistance: Ohms

-4 (-20)

4.70

10-20

32 (0)

3.40

4-7

68 (20)

2.50

2-3

104 (40)

2.00

0.9-1.3

140 (60)

1.20

0.4-0.7

176 (80)

0.70

0.2-0.4

⁽¹⁾	Measure resistance between sensor signal circuit and SIG RTN pin.

4) ECT Circuit Isolation Install breakout box. Leave ECA disconnected. Remove ECT connector. Check continuity between ECT and SIGRTN test pins. If continuity is present, repair circuit between ECT sensor and ECA. If continuity is not present, replace ECA.

5) ECT Sensor Resistance Disconnect ECT sensor. With key off, measure sensor resistance. Compare resistance to specifications shown in ECT SENSOR SPECIFICATIONS . If resistance is okay, repair circuit between ECT sensor and ECA. If resistance is not to specification, replace ECT sensor.