ECM Code EO15 - Open Coolant Sensor Circuit: Notes

TEST CONDITIONS:  Codes EO37 and EO38 clear. MAT sensor value greater than or equal to 5°C.

FAILURE CONDITIONS:  Coolant sensor value is less than or equal to -35°C (sensor signal open).

ACTION:  ECM turns on "ENGINE CONTROL SYSTEM" light. ECM commands BCM to display "SERVICE SOON" message on CCDIC panel. ECM turns off both AIR management solenoids. ECM uses MAT sensor value in place of coolant sensor value for all calculations.

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 pin "B" (circuit No. 410PC), and a sensor reference ground on pin "A" (circuit No. 476PC).

As temperature of sensor decreases, sensor resistance increases. Signal voltage from ECM to pin "B" increases as sensor temperature decreases and less current flows through sensor element to pin "A" (sensor ground). Code E015 sets because ECM assumes that coolant temperature can't be -35°C or less when MAT is 5°C or greater (sensor signal open to sensor).

1. If sensor is open, parameter ED04 should read -35°C or less. If not, sensor signal is not open. See NOTE ON INTERMITTENTS.
2. This step checks for open sensor signal in circuit No. 410 from ECM to sensor connector. If parameter ED04 reads 148-151°C with connector shorted, then circuit No. 410 is okay.
3. This step checks for open sensor ground (circuit No. 476) from ECM to sensor. If pin "B" to ground causes parameter ED04 to read 148-151°C, then there is an open in circuit No. 476 between sensor pin "A" and ECM terminal "D13".
4. This step checks the ECM's ability to recognize a short to ground or low voltage on pin "B8", coolant signal.
5. Fault is most likely at ECM connector or ECM. See CHART C1 - ECM REPLACEMENT CHECK before replacing ECM.