Electronic Control Module (ECM) Operation

The ECM is located under the passenger seat on "G" series vans. On all other models, the ECM is located inside the instrument panel, near the glove box. It controls the CCC system by constantly monitoring and adjusting engine operation. The ECM also monitors distributor reference pulses to measure engine RPM and to determine spark timing.

Information concerning cooling system temperature, crankshaft RPM, throttle blade position, manifold pressure and amount of oxygen in exhaust gases is continuously fed into the ECM while the engine is running. The ECM is designed to process this data sensor information, and programmed to send the electrical responses necessary to control the CCC system.

The ECM contains an engine calibration unit called a PROM. The PROM is located under an access cover within the ECM. The PROM contains specific instructions to tailor each ECM to individual vehicle design. Information such as vehicle size and weight, transmission, engine and final drive ratio are contained within the PROM. A PROM that is programmed for a particular vehicle cannot be used on another vehicle that does not have the same standards.