Code P086, Undefined Gear Ratio: Action

PCM turns on MIL. PCM de-energizes transaxle pressure control solenoid and torque management is disabled. Maintains transaxle shift adapts at current levels.

NOTE: Test numbers refer to numbers on diagnostic chart.

Install pressure gauges to transaxle.
Comparing gear box ratio (PD76) and transaxle pressure switch input (PD71) will determine what gear PCM was commanding and what possible gear ratio change resulted from such command.

Fig 1: Code P086 Schematic, Undefined Gear Ratio

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code P086 Diagnostic Flow Chart - 1 Of 2, Undefined Gear Ratio

Courtesy of GENERAL MOTORS CORP.

Fig 3: Code P086 Diagnostic Flow Chart - 2 Of 2, Undefined Gear Ratio

Courtesy of GENERAL MOTORS CORP.