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Home >> GMC Truck >> 1994 >> S15/T15 Jimmy 4WD V6-262 4.3L VIN Z >> Repair and Diagnosis >> Powertrain Management >> Transmission Control Systems >> Relays and Modules - Transmission and Drivetrain >> Relays and Modules - Transfer Case >> Control Module >> Description and Operation >> TCCM Inputs and Outputs >> TCCM Inputs >> Park/Neutral Position Switch Inputs

Park/Neutral Position Switch Inputs

Automatic Transmission Neutral Start Switch:




Neutral Start Switch Voltages:






OPERATION
Because range shift should only be made with the automatic transmission in neutral, the park/neutral position switch informs the Transfer Case Control Module (TCCM) that the vehicle automatic transmission is in either:

- Park
- Neutral
- One of the drive positions

The park/neutral position switch consists of three switches together in one unit, and it provides three signals:

- Park - When the automatic transmission is in park, the contacts of both the park switch and the park neutral switch are closed. When these contacts are closed, a battery voltage signal is sent to TCCM connector pin D2, while connector pin D16 is pulled to ground (0 voltage). The TCCM interprets this signal to mean the automatic transmission is in park.
- Neutral - When the automatic transmission is in neutral, the contacts of the park switch are open and the contacts of the park neutral position switch are closed. In this condition, a 0-voltage signal is sent to TCCM connector pin D2, while connector pin D16 is pulled to ground (0 volts). The TCCM interprets this signal to mean the automatic transmission is in neutral.
- In gear - When the automatic transmission is in any other gear position, the contacts of both the park switch and park neutral switch are open. In this condition, a 0-voltage signal is sent to TCCM connector pin D16. The TCCM interprets this signal to mean the automatic transmission is neither park or neutral.


Important

- If the backup switch connector were to be plugged in upside down, the park switch would receive no power. Such a condition would cause a 0-voltage signal at both pin D2 and pin D16 in neutral and in park. The transfer case, accordingly, would perform a range shift in park as well as in neutral.
- An open in circuit 75, or an open in the Turn/BU fuse would also cause this condition.
- Additionally, a park/neutral position switch that is out of adjustment may prevent a range shift in park.
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