* Faulty Window Switch: This is the most probable cause. The switch contains multiple contacts for up, down, and possibly lock functions. One or more of the contacts responsible for the "up" function may be broken, dirty, or worn out. Since the master switches work, it eliminates issues with the window motor, regulator, and most of the wiring. The switch is failing internally.
* Internal Switch Wiring: While less likely than a failed contact, a small internal wire break within the switch itself could isolate the "up" function.
* Switch Connector: Although less common, the connector at the switch itself could have a loose or damaged connection, particularly affecting a single function. Inspect for bent pins or corrosion.
* Rare Possibilities (Less Likely): A very subtle break in the wiring *exclusively* affecting the "up" signal to that specific switch is theoretically possible but less probable given the master switch functionality. A very specific ground problem could also contribute, although that would often affect multiple functions.
Troubleshooting Steps:
1. Check the obvious: Ensure nothing is physically blocking the window from going up.
2. Test other switches: Verify that the other window switches are functioning correctly.
3. Inspect the switch: Remove the switch (usually involves prying off a bezel) and visually inspect it for obvious damage or loose connections. Look closely at the connector pins.
4. Test with a multimeter (Advanced): If you're comfortable with basic electrical testing, you could use a multimeter to check for continuity across the switch contacts when attempting to raise the window. You'd need a wiring diagram to identify the correct pins to test. This requires caution to avoid electrical shock.
5. Replacement Switch: The most likely solution is replacing the faulty driver's side rear passenger window switch. These are relatively inexpensive parts and readily available.
In short, focus your attention on the switch itself. It's the most probable culprit given that the master switches function correctly. Replacing the switch is the easiest and most cost-effective troubleshooting step.
