* Faulty switch: The most common culprit is a problem with the switch that controls the motor. It might be stuck closed, shorted, or have a malfunctioning internal mechanism that prevents it from signaling the motor to stop. This could be the switch on the liftgate itself, or a switch inside the car's cabin.
* Wiring issue: A short circuit or break in the wiring harness leading to the motor could cause it to run continuously. This could be due to frayed wires, a pinched wire, or corrosion in the connectors.
* Bad motor: The motor itself might be faulty. The internal components that control its operation could have failed, causing it to run uncontrollably. This is less common than switch or wiring problems, but possible.
* Control module problem (less likely): In some cases, a problem with the car's body control module (BCM) or a similar electronic control unit could cause the motor to malfunction. This is less likely than the other causes but should be considered if the other possibilities are ruled out.
* Mechanical binding: Something might be obstructing the liftgate's movement, causing the motor to strain and continue running. Check for anything jamming the mechanism.
Troubleshooting Steps:
1. Check the switch(es): Start by carefully inspecting both the switch on the liftgate and the interior switch (if applicable). Look for anything obviously wrong, and try disconnecting them to see if the motor stops.
2. Inspect the wiring: Follow the wiring harness from the motor to the switch(es) and the control module. Look for any signs of damage, such as frayed wires, cuts, or corrosion.
3. Disconnect the motor: As a safety precaution, if the motor is still running, disconnect the power supply to the motor itself. This will stop it immediately, but you won't be able to use the power liftgate until the problem is resolved.
4. Check for obstructions: Manually try to lift the hatch and see if there's anything jamming its movement.
If you're not comfortable working with car electrical systems, it's best to take your Pontiac to a qualified mechanic for diagnosis and repair. Continuing to run the motor could damage it further.
