COMPUTER RELEARN PROCEDURES
Vehicles equipped with engine or transmission computers may require a relearn procedure after vehicle battery is disconnected. Many vehicle computers memorize and store vehicle operation patterns for optimum driveability and performance. When vehicle battery is disconnected, this memory is lost. The computer will use default data until new data from each key start is stored. As computer memorizes vehicle operation for each new key start, driveability is restored. Vehicle computers may memorize vehicles operation patterns for 40 of more key starts.
Customers often complain of driveability problems during relearn stage because vehicle acts differently then before being serviced. Depending on type and make of vehicle and how it is equipped, the following complaints (driveability problems) may exist:
Harsh Or Poor Shift Quality
Rough Or Unstable Idle
Hesitation Or Stumble
Rich Or Lean Running
Poor Fuel Mileage
These symptoms and complaints should disappear after a number of drive cycles have been memorized. To reduce the possibility of complaints, after any service which requires battery power to be disconnected, vehicle should be road tested.
GENERIC COMPUTER RELEARN PROCEDURES
Some manufacturers identify a specific relearn procedure which will help establish suitable driveability during relearn stage. These procedures are especially important if vehicle is equipped with and electronically controlled automatic transmission or transaxle. Always complete procedure before returning vehicle to customer. The following general procedures are to be used if driveability problems are encountered after power loss or battery has been disconnected. These procedures may provide an aid in eliminating these problems.
Set parking brake, start engine in "P" or "N" position. Warm-up vehicle to normal operating temperature or until cooling fan cycles.
Allow vehicle to idle for one minute in "N" position. Select "D" and allow engine to idle for one minute.
Accelerate at normal throttle position (20-50%) until vehicle shifts into top gear.
Cruise at light to medium throttle.
Decelerate to a stop, allowing vehicle to downshift, and use brakes normally.
Process may be repeated as necessary.
Sunday, July 18th, 2010 AT 7:44 AM