Failed Lamp Bulb
The vehicle’s system has detected a problem with one or more exterior lamps.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer is sensing that one of the lights on the vehicle, like a brake light or turn signal, isn’t working when it should be.
What the computer is actually seeing
The bulb monitoring system checks the voltage and resistance of each lamp circuit. If the voltage is outside of the expected range (typically near battery voltage), or if the resistance is too high indicating a fault in the bulb or circuit, it triggers the fault code.
What a healthy reading looks like
Expect around 12-14 volts at the bulb socket with the lights turned on; resistance should be below 10 ohms for a good circuit.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect all exterior lights visually (headlights, taillights, brake lights, turn signals).
- 22. Test each bulb; replace any that are burnt out before proceeding.
- 33. Check for corrosion or damage in the bulb sockets and connectors. Repair or clean as necessary.
- 44. Use a multimeter to measure voltage at each bulb socket with the lights on. Confirm it’s within the 12-14 volts range.
- 55. If any circuit shows low voltage, trace the wiring back to the control module checking for damage.
- 66. If the wiring is intact and voltage is good, test the control module for proper operation.
Common causes
- Burnt out bulb
- Corroded socket or connector
- Wiring damage or short to ground
- Faulty control module
Typical repair cost
$$
Related codes
Frequently asked questions
Can I drive the vehicle with this code active?
Yes, but you should fix light issues ASAP to avoid safety violations.
Will this code come back even after repairs?
If the root cause is fixed and connections are solid, it should not reappear.
Why did I get this code alongside SPN 1606?
SPN 1606 might indicate a problem with a different lamp circuit; check both circuits at once.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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