K 3500 Truck 4WD V8-6.6L DSL Turbo VIN 1 (2001)
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"7" (shifter should be in the Reverse position)
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"5" (shifter should be in the Drive position)
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"3" (shifter should be in the Third gear position)
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"2" (shifter should be in the Second gear position)
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"1" (shifter should be in the First gear position)
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"0" (shifter should be in the Neutral Position)
If the Gear Selected display does not match the shifter position in the vehicle, diagnose using one of the following methods.
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Obtain a new PNP switch kit, P/N 29540479, from the Parts Department.
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0.1. Disconnect the wiring connector from the original transmission mounted PNP switch.
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0.2. Connect the new switch to the wiring connector.
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0.3. Return to Step # 4 above and observe the display as you rotate the switch. If all positions indicate properly, refer to the Correction
section below.
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Use the DTC P0708 diagnostic chart in Service Information (SI) under Transmission/Transaxle/Automatic Transmission
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Allison. Reference SI Document ID # 769549 for the wiring schematic for this symptom.
The PNP switch, as referenced in SI, is known as the NSBU switch in the Parts information. It is now serviced with a Park Neutral Position Switch
Kit, P/N 29540479.
Flashing PRNDL Display
A flashing PRNDL display may be the result of incorrect sensor inputs or transmission abuse protection modes being received by the TCM. The
following are some of these conditions:
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The transfer case is/was in Neutral.
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The transfer case is/was shifted into Neutral when the vehicle is moving.
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A decrease of the input turbine speed was not detected when the gear selector was moved into any gear.
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A low transmission fluid level.
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A misadjusted PNP/NSBU switch.
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Turbine input speed or output speed sensor failure.
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Failures of the shift solenoids to route the transmission oil to the proper clutch assemblies within the transmission.
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Failures of the transmission clutch packs (C1 or C5 for first gear, C3 or C5 for Reverse).
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Failure to detect proper line pressures when a gear range is selected, which may be the result of normal maintenance such as a transmission
fluid change having been completed, or the transmission pan was removed for a filter replacement or other type service.
Transmission abuse protection modes are encountered when a customer performs one of the following types of maneuvers:
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Shifting from Neutral to Drive/Reverse when the engine RPM is greater than 1400 RPM.
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Shifting from Drive to Reverse when the throttle position (TPS) is greater than 25%, such as rocking the vehicle when stuck in an attempt to
free the vehicle.
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When the transmission output speed is greater than 300 RPM from attempted changes in direction such as Reverse to Drive, Drive to Reverse
or Neutral to Reverse shifts.
When the TCM encounters any one of the above conditions, the TCM will flash the PRNDL and default the transmission to Neutral. A flashing
