K 2500 Truck 4WD V8-6.5L DSL Turbo VIN S (1998)
Fluid Pressure Sensor/Switch: Description and Operation
4L80-E Automatic Transmission
AUTOMATIC TRANSMISSION FLUID PRESSURE MANUAL VALVE POSITION SWITCH ASSEMBLY
A gear range sensing device call an Automatic Transmission Fluid Pressure Switch (TFP Val. Position Sw.) Assembly is used by the VCM/PCM in
order to sense what gear range has been selected by the vehicle operator. The TFP Val. Position Sw. Assembly is located on the valve body and
consists of five pressure switches combined into one unit. The
VCM/PCM applies system voltage to the TFP Val. Position Sw. Assembly on three separate wires. These three circuits are either grounded or open,
depending on which gear range has been selected, and on which combination of the five switches have pressure applied to them.
When the vehicle is in PARK, with the key ON and the engine OFF, the normal state of the TFP Val. Position Sw. Assembly will be Drive 2. When
the key is ON and the engine is running, the normal state of the TFP Val. Position Sw. Assembly will be in PARK/NEUTRAL.
There are two possible combinations of the switches within the pressure switch manifold that do not represent an actual gear range. If the VCM/PCM
detects either of these combinations for more that 0.5 seconds, Code P1810 will set. Code P1810 will not set, however, if a valid gear range
combination appears at the wrong time.
While Code P1810 is present, the VCM/PCM will take the following actions:
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Assume Drive 4 for shift pattern control
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Maximize the line pressure
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The VCM will freeze shift adapts
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The MIL will not illuminate
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Type B code
If the TFP Val. Position Sw. Assembly resumes normal functioning, the transmission will resume normal operation after the next ignition cycle
