Theory Of Operation

WARNING: This page is about a different car, the 2017 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The Exhaust Gas Temperature (EGT) Sensors are used by the Powertrain Control Module (PCM) to monitor the engine exhaust temperatures in the aftertreatment system. The EGT Sensors are thermistors and change resistance based on the temperature being measured. EGT Sensors receive a 5-Volt signal from the PCM and share a sensor ground. The PCM monitors the change in signal voltage and converts this to a temperature value. The PCM illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails after two consecutive drive cycles. The PCM will turn off the MIL lamp after the diagnostic passes on four consecutive drive cycles. The PCM will disable active regeneration mode.

The first warning will occur when the p-code becomes pending or active. The customer will hear a chime and get an EVIC message reading "Service DEF System See Dealer." The second warning level will occur if the customer continues to drive and the code has not cleared. The customer will hear a chime and get an EVIC message reading "Speed Limited to 5 mph in XXX MILES See Dealer". Upon driving until the countdown reaches zero, the customer will hear a chime and get an EVIC message reading "5 mph Max on Restart, Long Idle or Refuel See Dealer." Upon key-off, refuel, or 1 hour long idle, the EVIC message will read, "Speed Limited to 5 mph See Dealer." Once induced to a 5 mph derate, the inducement will not clear unless the diagnostic runs and passes, or the PCM is recalibrated.