Diagnostic Aids

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Refer to Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic for the normal range signals and the illegal combinations.
DTC P1810 can be set falsely by low pump pressure, a stuck pressure regulator, or unit fill from overhaul and pan removal.
DTC P1810 can be set by a slipping forward clutch. It may allow the PCM to see a 2.08:1 ratio, reverse, when the manual valve position is indicated as D4.
DTC P1810 defaults to an elevated line pressure condition which may result in partial TCC apply. This may produce an idle surge that could stall the engine.