3500 4x4 Pickup V10-488 8.0L Magnum (1994)
Temperature Warning Indicator - A/T: Description and Operation
OPERATION
The transmission oil temperature warning lamp lights to indicate that the transmission oil is overheating. One side of the lamp bulb receives
battery voltage when the ignition switch is turned to the ON position. The other side of the bulb is grounded by the Powertrain Control Module
(PCM) when it senses transmission oil temperature is too high. A sensor mounted to the transmission cooler line sends a signal to the PCM
indicating transmission fluid temperature. This lamp is only used on vehicles equipped with a diesel or V-10 engine option and an automatic
transmission.
CIRCUIT OPERATION
Power for the transmission temperature sensor is supplied on circuit T54 from the Powertrain Control Module (PCM). Ground for the sensor is
supplied on circuit K4. This circuit is spliced and provides a common sensor ground for various sensors used in the engine control system.
Circuit T54 connects to cavity 42 of the PCM connector, and circuit K4 connects to cavity 4 of the connector.
The sensor is a variable resistor. When the PCM determines that the transmission oil temperature is above a predetermined level, it supplies a
ground path for circuit G14. This circuit is connected from the PCM to the message center warning lamp.
Circuit G14 connects to cavity 31 of the PCM on all engine packages except for the 8.0L V-10. On the 8.0L, the G14 circuit connects to cavity 36
of the PCM.
Power for the lamp is supplied to the message center on circuit F14. This circuit is HOT in the START and RUN position and is protected by a 15
amp fuse located in cavity 12 of the fuse block.
