Hi there:
The automatic Transmission Fluid Pressure (TFP) manual valve position switch consists of five pressure switches (two normally-closed and three normally-open), and a transmission Fluid Temperature (TFT) sensor combined into one unit. The combined unit mounts on the valve body.
The Powertrain Control Module (PCM) supplies ignition voltage for each range signal. By grounding one or more of these circuits through various combinations of the pressure switches, the PCM detects which manual valve position you select. The PCM compares the actual voltage combination of the switches to a TFP manual valve position switch combination chart stored in memory.
The TFP manual valve position switch cannot distinguish between PARK and NEUTRAL because the monitored valve body pressures are identical. With the engine OFF and the ignition switch in the ON position, the TFP manual valve position switch indicates PARK/NEUTRAL. Disconnecting the AT inline 20-way connector removes the ground potential for the three range signals to the PCM. In this case, with the engine OFF, and the ignition switch in the ON position, D2 will be indicated.
When the PCM detects an invalid state of the TFP manual valve position switch circuit by deciphering the TFP manual valve position switch inputs, then DTC P1810 sets.Action Taken When the DTC SetsThe PCM illuminates the Malfunction Indicator Lamp (MIL) during the second consecutive trip in, which the Conditions for Setting the DTC are met.The PCM commands D2 line pressure.The PCM commands a D4 shift pattern.The PCM freezes transmission adapt functions.The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.The PCM stores DTC P1810 in PCM history during the second consecutive trip in, which the Conditions for Setting the DTC are met.Since the computer does not know what gear range the transmission is shifted into, it defaults to a higher line pressure to protect the transmission. It also commands the transmission as if it were in the D4 position. The transmission will still shift normally through all the gears, shifts may be more firm than normal. No damage will occur to the transmission if driven even for prolonged periods with this dtc set. It is far more likely that the loss of transmission fluid damaged the transmission.
Hope helps.
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