Circuit/System Description

WARNING: This page is about a different car, the 2018 Chevrolet Suburban 3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The park/neutral position switch and the 5 Hall Effect switches are internal to and part of the internal mode switch assembly.

Park/Neutral Circuit

The park/neutral switch indicates to the engine control module (ECM) if the vehicle is in park/neutral or in a drive gear range. With the ignition ON, the ECM provides 12 V on the park/neutral signal to the park/neutral position switch. A separate ground wire from the park/neutral position switch to the Transmission Control Module (TCM) completes the path to ground. When the gear shift lever in park or neutral, the switch closes and drops the voltage on the signal circuit to 0 V. In this state the engine will start and run. In reverse or drive range the park/neutral switch opens, 12 V is then present on the signal circuit which will inhibit engine starting.

Hall Effect Switch Circuits

The internal mode switch indicates to the transmission control module (TCM) which gear position the vehicle operator has selected. The internal mode switch consists of 5 separate Hall Effect switches. Each Hall Effect switch is supplied a 9 V reference circuit and a signal circuit from the TCM. Each signal circuit for each gear selector position will have either a voltage reading of 0.70 - 0.96 V indicting On or 1.68 - 2.38 V indicating Off. The voltage values on each circuit will change and are dependent on the position of the gear selector. The state of each Hall Effect switch circuit is displayed on the scan tool.