Single Module Engine Controller (SMEC)
The SMEC contains the operating software, and performs calculations and adjustments necessary for engine operation. The SMEC is located at the front of the left fender panel in the engine compartment. See Fig 1 .
The SMEC is a microprocessor based digital computer, with 60-pin and 14-pin connectors. The SMEC receives input signals from various switches, sensors and other components. Using these signals, the microprocessor computes fuel injector pulse width, spark advance, ignition coil dwell, automatic idle speed actuation, canister purge cycle, cooling fan operation, and alternator output.
The SMEC also contains a diagnostic circuit to test input and output circuits. The diagnostic circuit will store information about any malfunctions as they occur for read-out prior to service. If the SMEC receives incorrect or no data from the MAP sensor, TPS sensor, CTS sensor, charge temperature sensor, or battery voltage sensor the SMEC will go into "Limp-In" mode. This mode turns on the "CHECK ENGINE" light and substitutes a modified signal for the failed component to keep the vehicle driveable. A DRB-II Tester (C-4805 ) or the flashing "CHECK ENGINE" light may be used in displaying trouble codes. However, the "CHECK ENGINE" light is limited in its diagnostic capabilities.