MEM-CAL Unit

To allow one ECM to be used for many different cars, a device called a Memory-Calibration unit or MEM-CAL is used. The MEM-CAL is located inside the ECM, and has calibration information based on the vehicle's weight, engine, transmission, axle ratio, and several other factors. While one ECM part number can be used by many car lines, the MEM-CAL is very specific and must be used for the right car.

It is very important to check the latest parts book and technical service bulletins for the correct part number when replacing the MEM-CAL. Parameter ED99 can be used to verify the proper PROM ID. An ECM used for service (called a Controller) comes without a MEM-CAL. The MEM-CAL from the old ECM must be carefully removed and installed in the new ECM, refer to 1989 REMOVAL, OVERHAUL & INSTALLATION -- ALLANTE article.

If the MEM-CAL is missing, it will result in a no start and no run condition, and the ECM will not send data to the BCM. A current code B334, refer to 1989 BODY COMPUTER MODULE -- ALLANTE article, and a "System Problem" message on the DIC will result.

The ECM performs the diagnostic function of the fuel control system. It can recognize operational problems, alert the driver through the "Engine Control System Fault" telltale, and store a code or codes which identify the problem areas to aid the technician in making repairs.