Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsLighting Systems Diagnosis and RepairMedium
A technician is troubleshooting a vehicle where the right taillight and right front parking light are not working, but the right turn signal and brake light function correctly in the same assembly. The left side lights work normally. What is the most likely cause?
- AAn open circuit in the parking light wiring specific to the right side
- BA blown fuse for the right side lighting circuit
- CA corroded ground connection shared by the right taillight and parking light
- DA faulty multi-function switch (turn signal/headlight stalk)
Show answer & explanationAnswer & explanation
Correct answer: C. A corroded ground connection shared by the right taillight and parking light
Since the right turn signal and brake light (which often share a ground with the taillight/parking light) are working, it suggests power is present. The selective failure of the taillight and parking light, often powered by different circuits but sharing a common ground, points to a compromised ground connection for those specific lights.
Why the other options are wrong
- A. An open circuit in the parking light wiring is possible, but the fact that both the taillight and parking light are out (and they are often separate filaments/bulbs in the same housing) points more towards a shared common issue like a ground.
- B. A blown fuse for the entire right side would affect all lights on that side, including the turn signal and brake light, which are working.
- D. A faulty multi-function switch could cause issues, but usually affects entire functions (e.g., all parking lights) or multiple independent circuits, not just specific lights on one side while others in the same assembly work.
Shared Ground Fault
When multiple components in a circuit fail, or act erratically, due to a poor or open common ground connection.
- Often causes dimness, erratic behavior, or no operation.
- Different circuits may share a common ground point.
- Can be isolated by checking continuity to ground for affected components.
Memory trick: Some work, some don't, ground's the stunt!