ECM Code EO14: Shorted Coolant Sensor Circuit: Action:

ECM turns on SERVICE ENGINE SOON light and uses MAT sensor value in place of coolant sensor value for all calculations for the first 4 minutes of operation. Then a value of 194°F (90°C) is used.

The coolant sensor is a variable thermistor. The coolant sensor is a 2-wire sensor with a signal voltage coming from the ECM to sensor terminal "B" (circuit No. 410), and a sensor reference ground on terminal "A" (circuit No. 976).

As sensor temperature increases, resistance decreases. Signal voltage from ECM to terminal "A" decreases as sensor temperature increases and current flows through sensor element to terminal "A" (sensor ground). Code E014 sets because ECM assumes coolant temperature can't be 298°F (148°C) or greater when MAT is 212°F (100°C) or less.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) With coolant sensor shorted, parameter ED04 should read 148°C or more. If not, sensor is not shorted. See NOTE ON INTERMITTENTS.

Test Number 2) This checks for a shorted coolant sensor or a short in circuit No. 410. If parameter stays at 142°C or greater with the sensor unplugged, then short is in circuit No. 410.

Test Number 3) Fault is most likely at ECM connector or ECM. See CHART C1, ECM REPLACEMENT CHECK before replacing ECM.