EMD Systems
EMD was required on all 2007 MY and beyond California gasoline and diesel fueled on-road heavy duty engines used in vehicles over 14,000 lbs GVWR. EMD systems are required to functionally monitor the fuel delivery system, exhaust gas recirculation (EGR) system, particulate matter trap, as well as emission related PCM 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 is employed, the only change being the addition of some comprehensive component monitor (CCM) rationality and functionality checks.
EMD vehicles use that same PCM, CAN serial data communication link, J1962 DLC, and PCM software as the corresponding OBD-II vehicle. The only difference is the possible removal of the rear oxygen sensor(s), 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 gasoline engine EMD calibrations
| Monitor/Feature | Calibration for Gasoline Engines |
|---|---|
| Catalyst Monitor | Not required, monitor calibrated out, rear O2 sensors may be deleted. |
| Misfire Monitor | Calibrated in for repair, all DTC are non-MIL. Catalyst damage misfire criteria calibrated out, emission threshold criteria set to 4%, enabled between 66°C (150°F) and 104°C (220°F), 254 second start-up delay. |
| Oxygen Sensor Monitor | Rear heated oxygen sensor (HO2S) test calibrated out, rear HO2S may be deleted, front HO2S response test calibrated out. |
| EGR Monitor | Same as OBD-II calibration except that DTC P0402 test uses a higher threshold. |
| Fuel System Monitor | Same as OBD-II calibration. |
| Secondary Air Monitor | Functional (low flow) test calibrated out, circuit codes are same as OBD-II calibration. |
| Evaporative Emission (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 (CCM) | All circuit checks, rationality and functional tests are the 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. |
| MIL Control | Same as OBD-II, it takes two drive cycles to illuminate the MIL. |
GASOLINE ENGINE CALIBRATION REFERENCE
The following monitor descriptions provide a general description of each OBD monitor. In these descriptions, the monitor strategy, hardware, testing requirements, and methods are presented to provide an overall understanding of monitor operation. An illustration of each monitor may also be provided. These illustrations should be used as typical examples and are not intended to represent all possible vehicle configurations.
Each illustration depicts the PCM as the main focus with primary inputs and outputs for each monitor. The icons to the left of the PCM represent the inputs used by each of the monitor strategies to enable or activate the monitor. The components and subsystems to the right of the PCM represent the hardware and signals used while carrying out the tests and the systems being tested. The CCM illustration has numerous components and signals involved which are shown illustration generically. When referring to the illustrations, match the numbers to the corresponding numbers in the monitor descriptions for a better comprehension of the monitor and associated DTCs.
These icons are used in the illustrations of the OBD monitors and throughout this information.
