Diagnostic Aids

Scan tester only indicates when PCM has commanded TCC on. This does not indicate TCC is actually engaged. To determine if TCC is engaging, road test vehicle. Engine RPM should decrease when scan tester indicates TCC engagement.

Fig 1: Code 39, Schematic, TCC Circuit 3.8L

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 39, Flow Chart, TCC Circuit 3.8L

Courtesy of GENERAL MOTORS CORP.