RAM 3500 Truck 4WD V10-8.0L VIN W (1997)
Wait To Start Light: Description and Operation
SYSTEM OPERATION
Vehicles equipped with an optional diesel engine have a wait-to-start lamp. The wait-to-start lamp gives an indication that the conditions for
easiest starting of the diesel engine have not yet been achieved. The wait-to-start lamp bulb in the message center is lighted by the Powertrain
Control Module (PCM), after the ignition switch is turned to the On position.
One side of the wait-to-start lamp bulb receives battery voltage when the ignition switch is turned to the On position. The PCM switches the
ground path for the other side of the bulb based upon several inputs and its internal programming.
The wait-to-start lamp lets the driver know that the intake manifold air heater grid has had sufficient time to warm the intake air for a good quality
start. The intake manifold air preheat cycle is controlled by an electronic air heater control module. The lamp will be turned off by the PCM when
the heater control module cycle is completed, or if the driver turns the ignition switch to the Start position prior to the end of the heater control
module cycle.
This lamp is illuminated by the PCM based on the input from the charge air temperature sensor. This light is illuminated when the ignition switch
is turned to the ON position. It remains on for two seconds as a bulb test.
If the PCM receives a signal from the charge air temperature sensor indicating that the intake air temperature is at or below 59°F (15°C), and if the
PCM has not received an engine crank signal, then the PCM will illuminate the Wait-To-Start lamp. If this light is illuminated, it indicates that the
intake air heaters have been ENERGIZED and the preheat cycle has begun. This light remains illuminated until; the preheat cycle is finished, or
the PCM receives an engine crank signal.
The Wait-To-Start lamp will flash ON and OFF if the charge air temperature sensor input to the PCM is above maximum value or below minimum
value. If either of the previous conditions occur, a DTC will be stored in the PCM's memory.
