Memory Loss

The VCM control calibrations for a particular vehicle are based on the Vehicle Identification Number (VIN). The calibrations are stored in the Electrically Erasable Programmable Read Only Memory (EEPROM). The EEPROM is part of the VCM and can not be replaced. The EEPROM can be reprogrammed using the Techline equipment.


The VCM has the ability to make corrections in the fuel control system to allow for minor vehicle variations. This information is stored in the Random Access Memory (RAM). RAM needs a constant voltage supply to be retained. Short Term Fuel Trim and Long Term Fuel Trim are stored in RAM. When the battery is disconnected during service of the vehicle this memory is lost and the driver may notice a change in the performance of the vehicle. In order to restore this memory perform the following steps:
1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. Drive the vehicle under idle, partial throttle and moderate acceleration conditions.
4. Continue until normal vehicle performance returns.