Test Description

WARNING: This page is about a different car, the 1995 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Test numbers refer to numbers on diagnostic chart.

The 1-4 upshift light should not turn on. If light is on, circuit is shorted to ground or PCM is faulty.
PCM should turn on 1-4 upshift light.
Checks 1-4 upshift light circuit up to PCM connector. If light illuminates, PCM connector is faulty or PCM does not have ability to ground circuit.

Fig 1: Code 91 Schematic (Corvette) 1-4 Upshift Light

Fig 2: Code 91 Diagnostic Flow Chart (Corvette) 1-4 Upshift Light