E014

TEST CONDITIONS
1. Codes EO37 and EO38 not set;
2. MAT temperature less then or equal to 100°C.

FAILURE CONDITIONS
Coolant sensor signal equal to or greater than 148°C (Sensor signal shorted to ground).

ACTION TAKEN
1. ECM turns on "Engine Control System" telltale;
2. ECM commands BCM to display "Service Soon" message on Driver Information Center (DIC);
3. ECM disables AIR Management valves;
4. ECM uses the MAT sensor values in place of the coolant temperature sensor.

DESCRIPTION
The coolant sensor is a thermistor, a sensor whose resistance varies with temperature. The coolant sensor is a "two wire" sensor with sensor signal on CKT 410 (Pin B) to the ECM and sensor ground on CKT 1076 (Pin A) to the ECM. As the temperature of the sensor increases, resistance decreases. As resistance decreases, the ECM sees less voltage drop across the sensor and interprets it as high coolant temperature. High coolant temperature will result in low signal voltage on CKT 410 and low coolant temperature results in high signal voltage on CKT 410. Code EO14 "Shorted Coolant Sensor" sets because the coolant temperature cannot be greater than 148°C (298°F) when the MAT is less than 100°C (212°F).

Notes on Fault Tree
1. With the coolant sensor or wiring shorted, ECM Data EDO4 will read 148°C or greater. If not, then the sensor or wiring is not shorted: see "Note on Intermittents."
2. Checking for sensor shorted or CKT 410 shorted. If the parameter value stays at 142°C or greater with the sensor unplugged, the short is in CKT 410 between sensor Pin "B" and ECM terminal F16.
3. Checking for faulty mating of ECM connector. Fault is most likely at the ECM connector. Before replacing ECM perform "ECM replacement check", Chart C-1. Chart C-1 Vehicle Will Not Enter Diagnostics

NOTES ON INTERMITTENTS
Manipulate CKT 410 wiring, coolant sensor connector, and ECM connector while observing ECM Data ED04. If the coolant temperature jumps from a normal reading to 148°C or greater, repair the intermittent short to ground on CKT 410. Remove and reconnect both the Coolant and ECM connectors and retest before replacing any components. If wiring and connectors check out OK, substitute a known good coolant sensor and retest.