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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 72 (Automatic Transmission Diagnosis - 4L80-E (Diesel)) >> Description & Operation >> Adapt Function >> 1-2, 2-3 & 3-4 Upshift Adapts

1-2, 2-3 & 3-4 Upshift Adapts

WARNING: This page is about a different car, the 2002 GMC Cab & Chassis Sierra and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The PCM monitors the transmission Input Speed Sensor (ISS) and the Output Speed Sensor (OSS), to determine when the transmission has started, and completed an upshift. The PCM looks at the time from the beginning, until the completion of the upshift. If the time of the upshift was longer than a calibrated value, then the PCM adjusts the current to the Pressure Control (PC) solenoid to increase line pressure for the next upshift under identical conditions. If the time of the upshift was shorter than a calibrated value, then the PCM adjusts the current to the PC solenoid to decrease line pressure for the next upshift under identical conditions.

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