False Bulb Failure indications aren't uncommon after several years. Here is how the system works, and some things to check for false lights—

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The Bulb Failure Sensor tests for a current balance in each of these three groups of light pairs (includes 3 bulb brake lights):

• Tail lights
• Brake lights
• Low headlight beams

You can isolate the problem to one of these groups as described below. The car must be running to activate the Bulb Failure sensor:

1 – Step on Brakes.... If no Warning light,
2 – Turn Parking (tail) lights on.... If still no Warning light,
3 – Turn on Low beams. Should be the cause of the Warning light.

If Warning light is ON when all these lights are OFF (or all tested lights are OK), it could be the BF Sensor at fault.

However, "mismatched" bulbs (different brands, age, or socket condition), or corrosion at the common ground points for Left & Right light housings ) in any of the 3 light groups can also cause a false BF light.

Note that there will be NO warning if BOTH bulbs in a pair are out.

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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.