A technician is diagnosing an intermittent issue where the vehicle's turn signals sometimes 'hyperflash' (flash rapidly) on one side, even though all bulbs appear to be working. A visual inspection of the bulbs and wiring on the affected side shows no obvious issues. What is the MOST likely cause of this hyperflashing condition?
- AA short to ground in the turn signal wiring.
- BA faulty turn signal switch.
- CAn incorrect wattage bulb installed in the circuit.
- DA faulty flasher relay or Body Control Module (BCM).
Show answer & explanationAnswer & explanation
Correct answer: C. An incorrect wattage bulb installed in the circuit.
Hyperflashing is a built-in safety feature in most modern vehicles, designed to alert the driver to a burned-out bulb by sensing a change in current draw (resistance) in the circuit. If all bulbs appear to be working, an incorrect wattage bulb (one with lower resistance, drawing more current, or higher resistance, drawing less current, than specified) can trick the flasher unit or BCM into thinking a bulb is out or an anomaly exists, leading to hyperflashing. This is often seen with aftermarket LED bulbs without proper resistors.
Why the other options are wrong
- A. A short to ground would likely blow a fuse or keep the light on solid, not cause hyperflashing with bulbs working.
- B. A faulty turn signal switch would likely cause no signal or an inconsistent signal, not hyperflashing with all bulbs working.
- D. While possible, a faulty flasher/BCM is less likely if the hyperflashing is specific to one side and occurs when all bulbs are visually working. An incorrect bulb is a more common and specific cause for this symptom.
Hyperflashing Diagnosis
Rapid flashing of turn signals, typically indicating a bulb is out or there's an incorrect load in the circuit, often due to a change in resistance.
- A safety feature to alert the driver of a bulb failure.
- Caused by a decrease in current draw (burned-out bulb) or an unexpected change in resistance (incorrect bulb type).
- Often seen with LED bulb replacements without load resistors.
Memory trick: Fast flash, check the watts, or the module's got a glitch.