E059

TEST CONDITIONS
1. Codes EO14 and EO15 not set;
2. Vehicle speed equal to or greater than 10 MPH for 600 seconds.

FAILURE CONDITIONS
Transmission temperature less than or equal to -39°C when the coolant temp is equal to or greater than 50°C or Transmission temperature equal to or greater than 148°C when the coolant temp is less than or equal to 50°C.

ACTION TAKEN
1. ECM turns on "Engine Control System Fault" telltale;
2. ECM commands BCM to display "Service Soon" message on Driver Information Center (DIC);
3. ECM substitutes 110°C for transmission temperature.

DESCRIPTION
The transmission temperature sensor is a thermistor, or variable resistor, that varies in resistance based on temperature. The sensor is a "two-wire" sensor with a reference signal coming from the ECM to the sensor on Pin A (CKT 520) and a sensor reference ground on Pin B (CKT 476). As the temperature of the sensor increases, sensor resistance decreases. As the resistance decreases, the signal voltage from the ECM decreases due to the less voltage drop across the transmission temperature sensor. High temperature will result in low signal voltage on CKT 520 and low temperature will result in high signal voltage on CKT 520.

The ECM uses transmission temperature information to vary Viscous Converter Clutch (VCC) apply speeds, 2-3 shift points, and 3-4 shift points.

Code EO59 will set the ECM sees a excessively low or excessively high VCC temperature when the coolant is hot or cold, respectively.

Notes on Fault Tree
1. VCC sensor circuit is shorted to ground.
2. VCC sensor circuit is open.

Notes on Intermittents
Manipulate the transmission connector, ECM connector, and CKT 520 wiring while observing ECM parameter ED26. If the fault is induced, the data value will jump from a normal reading to a low or high reading. Repair the intermittent. short to ground or open in CKT 520.

Disconnect and reconnect the ECM and transmission connectors and ensure they are latched. If wiring and connectors check out OK, substitute a known good transmission temperature sensor and retest.