A vehicle's left front parking light and left rear taillight are both inoperative. However, the left front turn signal, left rear turn signal, and brake lights all function correctly. Both the right side parking light and taillight are operating normally. What is the MOST likely cause?
- AA defective left front parking light bulb and a defective left rear taillight bulb.
- BA faulty multi-function switch.
- CAn open circuit in the ground wire shared by the left front parking light and left rear taillight.
- DA blown fuse dedicated to the left side parking and taillight circuit.
Show answer & explanationAnswer & explanation
Correct answer: D. A blown fuse dedicated to the left side parking and taillight circuit.
The failure of both the left front parking light and left rear taillight, while other lights on the left side (turn signals, brake lights) and the right side parking/taillights work, strongly suggests a common power supply issue to these specific lights. A dedicated fuse for the left side parking/taillight circuit would explain this isolated failure.
Why the other options are wrong
- A. While possible, the simultaneous failure of two unrelated bulbs (front parking and rear taillight) is less likely than a single point of failure in their shared power supply, such as a fuse.
- B. A faulty multi-function switch typically controls multiple functions (headlights, turn signals, wipers) and a fault would likely affect more than just these two specific lights, or affect them differently.
- C. An open ground shared by these two lights would cause both to fail. However, it's less common for parking lights and taillights to share a *single* ground wire separate from other lights on that side, and a blown fuse is a more direct and common cause for a shared power loss.
Shared Power Circuit Fault
When multiple, seemingly disparate lights fail simultaneously but other lights on the same side or in the same assembly function, it often indicates a common power supply issue, such as a blown fuse or an open in a shared power wire.
- Multiple lights fail together.
- Other lights in the same assembly/side still work.
- Points to a common power feed interruption.
- Fuse is a common culprit for shared power loss.
Memory trick: Left front park and left rear tail are out. They're probably sharing a fuse like roommates sharing rent.