EMD Systems

Engine Manufacturer Diagnostics (EMD) - Heavy duty vehicles (>14, 000 GVWR) certified to EMD under title 13, CCR section 1971 (e.g., 2007-2009 model year diesel and gasoline engines)

Engine Manufacturer Diagnostics (EMD) applies to all 2007 MY and beyond California gasoline-fueled and diesel fueled on-road heavy duty engines used in vehicles over 14, 000 lbs Gross Vehicle Weight Rating (GVWR). EMD systems are required to functionally monitor the fuel delivery system, exhaust gas recirculation system, particulate matter trap, as well as emission related ECM input inputs for circuit continuity and rationality, and emission-related outputs for circuit continuity and functionality. For gasoline engines, which have no PM trap, EMD requirements are very similar to current OBD-I system requirements. As such, OBD-I system philosophy will be employed, the only change being the addition of some comprehensive component monitor (CCM) rationality and functionality checks.

Engine Manufacturer Diagnostics Enhanced (EMD+) - Heavy-duty engines (>14, 000 GVWR) certified to EMD+ under title 13, CCR section 1971.1 (e.g., 2010-2012 model year diesel and gasoline engines not certified to HD OBD, 2013-2019 model year alternate fuel engines)

Starting in the 2010 MY, EMD was updated to require functional monitoring of the NOx after treatment system on gasoline engines. This requirement is commonly known as EMD+.

EMD+ vehicles use that same PCM, CAN serial data communication link, J1962 Data Link Connector, and PCM software as the corresponding OBD-II vehicle. The only difference is the possible removal of the fuel tank pressure sensor, canister vent solenoid, and a different PCM calibration.

The following list indicates what monitors and functions have been altered from OBD-II for EMD calibrations:

Monitor/Feature	Calibration
Catalyst Monitor	Functional catalyst monitor required starting in the 2010 MY to meet EMD+.
Misfire Monitor	Calibrated in for service, all DTCs are non-MIL. Catalyst damage misfire criteria calibrated out, emission threshold criteria set to 4%, enabled between 150 °F and 220 °F, 254 sec start-up delay.
Oxygen Sensor Monitor	Front O2 sensor "lack of switching" tests and all circuit and heater tests calibrated in, response/delay test calibrated out. Rear O2 sensor functional tests and all circuit and heater tests calibrated in, response/delay test calibrated out.
EGR/VVT Monitor	Same as OBD-II calibration except that P0402 test uses slightly higher threshold.
Fuel System Monitor	Fuel monitor and FAOSC monitor (rear fuel trim for UEGO systems) same as OBD-II calibration, A/F imbalance monitor calibrated out.
Secondary Air Monitor	Not applicable, AIR not used.
Evap System Monitor	Evap system leak check calibrated out, fuel level input circuit checks retained as non- MIL. Fuel tank pressure sensor and canister vent solenoid may be deleted.
PCV Monitor	Same hardware and function as OBD-II.
Thermostat Monitor	Thermostat monitor calibrated out.
Comprehensive Component Monitor	All circuit checks, rationality and functional tests same as OBD-II.
Communication Protocol and DLC	Same as OBD-II, all generic and enhanced scan tool modes work the same as OBD-II but reflect the EMD calibration that contains fewer supported monitors. "OBD Supported" PID indicates EMD ($11).
MIL Control	Same as OBD-II, it takes 2 driving cycles to illuminate the MIL.

EMD system implementation and operation is a subset of OBD-II and is described in the remainder of this document.