October 30: LEMON manuals on a temporary server, it is slow and having issues, download the manuals you need! Later in November we will switch back to the fast server.

Diagnostic Aids

Inspect harness and all related connections, including PCM connections. These may cause an intermittent code to set.

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

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