The backup lamps will light whenever the ignition switch is in the RUN position and the transaxle is in REVERSE. On older vehicles, this function was handled by a dedicated switch with a name such as the Neutral/Safety Backup Light Switch, or something similar. This switch was designed to keep the engine from starting in any gear except PARK and/or NEUTRAL. The switch contacts also activated the backup lights when the transaxle was placed in REVERSE.
On the vehicles covered by this guide, the backup lamp control function is part of an integrated switch called the Transaxle Range switch (sometimes also called the Park/Neutral Position or PNP switch). In addition to turning on the backup lights, the Transaxle Range switches primary function is to transmit to the Powertrain Control Module (PCM) the driver's transaxle range selection. The PCM uses this information to control both engine and transaxle functions electronically.
The Transaxle Range switch is mounted externally on the transaxle. New service replacement switches come pinned in the NEUTRAL position and no adjustment should be necessary. Please note that if the switch requires adjustment, GM recommends that their special tool J 41545 Park/Neutral Switch Alignment Tool be used to properly adjust the Transaxle Range switch, if required.
The transaxles used in the vehicles covered by this guide are all electronically controlled, under the command of the Powertrain Control Module (PCM). GM recommends that professional technicians perform this test before any further diagnostic work is done to make sure that the electronic control inputs are connected and operating. If a technician does not check the inputs before operating the transaxle, it is very possible to misdiagnose a simple electrical condition as a major transaxle condition.
- Start the engine.
- Firmly depress the brake pedal.
Move the gear selector to the following positions:
- PARK to REVERSE
- REVERSE to NEUTRAL to DRIVE
- Gear selections should be immediate and not harsh.
Because the transaxle is under the control of the PCM, certain conditions will cause Diagnostic Trouble Codes (DTCs) to set. A qualified technician using a scan tool connected to the vehicle's Data Link Connector (DLC) should be able to read and interpret the codes to help diagnose transaxle performance issues.
REMOVAL & INSTALLATION
- Apply the parking brake and block the front wheels.
- Place the transaxle gear selector to NEUTRAL.
- Remove the air intake duct to access the switch located on the top of the transaxle at the range selector cable and arm.
- Disconnect the transaxle range selector cable.
- Detach the electrical connectors from the range selector switch.
- Remove the range selector lever retaining nut and lift off the lever.
- Unfasten the range selector switch mounting bolts, then remove the switch from the transaxle manual shaft. Note that the manual shaft should have flat area which registers with a flat area on the switch.
- A service replacement range selector switch should come with a small pin holding the switch in NEUTRAL. The transaxle itself should still be in NEUTRAL from the removal procedure. Align the flats of the transaxle manual shaft to the flats in the switch and install the switch. Install, but do not tighten the mounting bolts.
- Tighten the mounting bolts to 18 ft. lbs. (25 Nm). Do not overtighten.
- Install the transaxle range selector lever to the manual shaft, install the nut to 15 ft. lbs. (20 Nm).
- Attach the electrical connectors.
- Connect the transaxle range selector cable.
- After switch installation, verify that the engine will only start in the PARK or NEUTRAL positions. If the engine will start in any other position, readjust the switch and/or check the shifter and shifter cable.