E015

Code E015:

Sensor Circuit:

DESCRIPTION:

The coolant sensor which is located behind the distributor on the thermostat housing, is a thermistor, a sensor whose resistance varies with temperature. The coolant sensor signal is on CKT 410 and sensor ground on CKT 976. As the temperature of the sensor increases, sensor resistance decreases. A high coolant temperature will result in low signal voltage on CKT 410. Code E015 "Open Coolant Sensor" sets because the ECM assumes that coolant temperature can't be less than -38°C when the MAT is greater -5°C.

TEST CONDITIONS:

1. Code E037 and E038 clear.
2. MAT Sensor value -5°C or greater.

FAILURE CONDITIONS:

Coolant Sensor Value -38°C or greater.

ACTION TAKEN:

1. ECM turns on "SERVICE ENGINE SOON" telltale.
2. 2. ECM uses the MAT sensor values in place of coolant temperature sensor for the first four minutes of engine operation, then the value of 90°C is used.

NOTES ON FAULT TREE:

1. With sensor or wiring open circuited, parameter ED04 should read -38°C or less. If not, then the sensor or wiring is OK, see NOTE ON INTERMITTENTS.

2. Checking for an open sensor signal in CKT 410 from the ECM to sensor connector. If parameter ED04 reads 148°C to 151°C with connector shorted then CKT 410 is OK.

3. Checking for an open sensor ground CKT 976 from pin A to the ground splice. If pin "A" to ground causes ED04 to read 148°C to 151°C then there is an open in CKT 976.

4. Checking for the ECM's ability to recognize a low voltage on terminal E16, coolant sensor input. If grounding terminal E16 causes ED04 to show 148°C to 151°C, then there is an open in CKT 410 from the ECM to the coolant sensor.

5. Checking for faulty mating of the ECM connectors. Fault is most likely at the ECM connector or the ECM. Before replacing the ECM, perform "ECM Replacement Check", Chart C-1.

NOTE ON INTERMITTENTS:

Manipulate CKT 410 wiring, the coolant sensor and ECM connector while observing ECM Parameter EDO4. If the failure is induced, the coolant temperature will jump from its normal value to the shorted reading of 148°C, repair the intermittent short to ground on CKT 410 or 976. Remove and replace both the COOLANT and ECM connectors and ensure that they are latched. If wiring and connector check out OK, substitute a known good coolant sensor and retest.