RAM 2500 Truck 4WD L6-5.9L DSL Turbo VIN 6 (1999)
Emissions Maintenance Light: Description and Operation
Whenever the Engine Control Module (ECM), or the Powertrain Control Module (PCM) sets a Diagnostic Trouble Code (DTC) for an emission
related item, it illuminates the Malfunction Indicator Lamp (MIL). The MIL is displayed on the instrument panel as the CHECK ENGINE lamp. The
MIL will only be illuminated for DTC's that affect vehicle emissions.
There are some monitors that may take two consecutive trips to illuminate the MIL if a DTC has been detected. The MIL will stay on continuously (if
key is ON) when the ECM or PCM has entered a Limp-In mode or has identified a failed emission component.
The MIL either flashes or illuminates continuously when the PCM detects active engine misfire.
Additionally, the ECM or PCM may reset (turn off) the MIL if a previous malfunction (DTC) has not been re-detected after 2 consecutive trips have
occurred.
The MIL will illuminate at key-on and will stay lit for approximately 2 seconds if the engine has not been cranked over. This is done as a bulb check
(bulb test).
