Clutch Pulse Learn Description

Clutch Pulse Learn Description

Clutch Pulse (CP) Learn is an enhancement to the Transmission Adaptive Functions Transmission Adaptive Functions.

The 6T30/40/45 transmission uses a pressure control system to apply and release clutches during shifts. The transmission control module (TCM) controls pressure commands to the pressure control solenoids. As normal wear of the transmission clutches occur and clutch pack running clearance increases, the piston has to travel farther and the volume of transmission fluid required to move the clutch piston to the point of clutch apply increases, effecting the time it takes to get the clutch to the point of apply, also known as fill time. The clutch return springs are compressed to a different length, which changes the force the springs apply on the piston.

To compensate for the normal wear or change of components, the TCM performs a CP Learn to determine the clutch fill time and spring force. The TCM momentarily commands a clutch on at low pressure. The pressure pulse commands are increased until an interruption in transmission input speed is detected. The return spring force is the first characteristic to be learned. After the spring force is learned, the TCM uses different pulse commands to determine the volume of transmission fluid required to move the clutch piston to the point of clutch apply. The TCM calculates fill time based on the learned volume.

The CP Learn is conducted during steady conditions in 3rd, 5th and 6th gear. The CP Learn for the 4-5-6 clutch is enabled in 3rd gear. CP Learn for the 1-2-3-4 clutch and 2-6 clutch is enabled in 5th gear. CP Learn for the 3-5-R clutch is enabled in 6th gear. A rough road condition could give a false reading for transmission input speed interruption. When rough road conditions are detected, CP Learn is aborted until road conditions improve.

When a CP Learn is occuring a slight bump or drag may be detected momentarily. The CP Learn will occur on the average vehicle every 1250 miles (2012 km). This is a normal condition and no repair attempts should be preformed.

The frequency of CP Learn is normally determined by the number of clutch apply cycles. The TCM will also initiate a CP Learn in advance of the clutch apply counter if shifts are detected which indicate an improper clutch fill time.