Some GM vehicles are equipped with GM Oil Life System (GMOLS) that calculates an optimal oil life change interval depend on driving conditions and climate. And for more GM vehicles projects,check here:GM vehicle repair cases
The GMOLS system is not a mileage counter. It is actually a computer based software algorithm that determines when to change oil based on engine operating conditions. There is no actual oil condition sensor. Rather, the computer continuously monitors engine-operating conditions to determine when to change oil. Over the years, millions of test miles have been accumulated to calibrate the system for a variety of vehicles. The system was first introduced in 1988 and is now on more than 18 million GM vehicles.
An engine controller stores GMOLS parameters as an Oil Life Reminder that is measured in percents. 100% means that the oil is new, 0% means that the oil must be changed immediately. GMOLS automatically decreases the Oil Life Reminder while the vehicle is being driven. When the Oil Life Reminder goes close to zero, the Change Oil Light appears on the vehicle control board. The Oil Life
Reminder must be reset every time the oil is changed. Some vehicles support the Oil Life Reminder reset from the vehicle control panel, but there are some vehicles that can be reset by a diagnostic tool only.
Engine reprogramming may change or reset the Oil Life Reminder. In order to support correct oil change intervals after reprogramming, the Oil Life Reminder must be set to the value that it has before reprogramming. The Service Programming Assistant lets retrieving the current Oil Life Reminder and setting it to any value between 0% and 100%. The recommended procedure is:
1) Analyze the controller before reprogramming.
2) Retrieve the Oil Life Reminder and remember it.
3) Reprogram the controller.
4) Analyze the reprogrammed controller and retrieve the Oil Life Reminder.
5) If the new Oil Life Reminder is different from the Oil Life Reminder
before reprogramming, send the old Oil Life Reminder to the controller.
6) Retrieve the Oil Life Reminder to ensure that it has been successfully sent.
If a controller has been reprogrammed and the old Oil Life Reminder is unknown, it is recommended to change the oil and reset the Oil Life Reminder (set it to 100%). If the oil has been changed within last 500 miles, the Oil Life Reminder may be reset without the oil change. Otherwise, if the customer does not want to change the oil, do not reset the Oil Life Reminder and recommend him to change the oil after 3000 miles from the last oil change and reset the Oil Life Reminder then.