Diagnostic Aids

The PCM/TCM relies on the Pressure Switch Manifold (PSM) to indicate what gear range has been selected. PSM must be functioning properly or Code 85 may be set. Check all connections, especially those at the transmission pass-thru connector. If code is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section. Compare Scan tester gear ratio reading to specifications in GEAR RATIO table.

Fig 1: Code 85 Schematic - Undefined Ratio

Fig 2: Code 85 Flow Chart - Undefined Ratio