Exhaust Pressure Control Valve Low
– Exhaust Back Pressure Valve harness is open or shorted
– Exhaust Back Pressure Valve poor electrical connection
If the ECM detects an Exhaust Back Pressure (EBP), Engine Oil Temperature (EOT) or Intake Air Temperature (IAT) sensor fault it will disable the exhaust back pressure regulator.
Exhaust Back Pressure Regulator – Is a variable position valve that controls exhaust back pressure during cold ambient temperatures to increase cab heat and decrease the amount of time needed to defrost the windshield. The Engine Control Module (ECM) uses the measured exhaust back pressure, (ambient) intake air temperature, engine oil temperature and engine load to determine the desired exhaust back pressure. Valve position is controlled by switching the output signal circuit to 12 volts inside the ECM. On/off time is modulated from 0 to 99 % dependent upon the exhaust back pressure desired.
Upon each initial engine start-up, the ECM exercises the exhaust back pressure valve by commanding it to cycle on and off once. If upon start-up the temperature of intake air sensed by the Intake Air Temperature (IAT) sensor is < 37