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I have a 2011 Opel Astra J that shows two notices on start-up:

  • broken right city light (message shown is in Dutch, my translation)
  • service brake lights (message shown is in Dutch, my translation).

While the light seems to work fine.

Originally only the first notice was shown. The right tail light was emitting light, but I replaced it none the less. This did not resolve the issue, message was still shown.

When switching both rear bulb-mounting assemblies (left and right, plugs are compatible), the message remains that the right tail light bulb is defective.

If I unplug the left tail light assembly, a message is shown for both left and right tail lights.

Measuring the voltage over both left and tail light (at the level of the metal conducting strips in the tail light assemblies) gives the exact same value, 11.48V when battery voltage is approximately 12.5V.

Measuring the voltage from another ground to the negative bulb terminal yields 40mV.

There's one present DTC in the BCM, B3881-04 - Rear Left Tail Light Circuit Open. Status:Present

I suspect this saying "left" rather than "right" is an error in the ScanMyOpelCAN application.

Some other DTC's regaring rear wiper, windshield washer pump relay, front washer relay circuit and high speed comunication enable circuit are logged but not active.

If it were a grounding issue, would the voltage over the right bulb not be less than the voltage over the left bulb?

Any ideas?

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Do you know how, in the TV series House M.D., Dr House would yell at his associates if they suggested the patient's symptoms could be explained by two unrelated diseases occurring simultaneously?

Well, sometimes two unrelated diseases occur simultaneously. Three diseases if stupidity on my part counts.

It turns out that

  1. There are "rear tail lights" ("rechter stadslicht" in Dutch according to the car, although if you were to ask people "please point to your "rechter stadslicht" almost no-one would be able to answer you) in both the hatchback lift-gate and the stationary part of the car.
  2. Often times, when the BCM detect a light is out, it will turn on a different light in the same assembly, often even with the same reflector. So from the outside of the car, you won't be able to tell the difference.
  3. According to the Haynes manual, in Vauxhall editions there's even a bulb in the front headlight assembly which, when broken, could set the same error. I looked and looked but on my particular car it appears no such bulb exists.

So yeah, there was both a W5W tail light broken in the rightmost tail light, and a W16W in the left one. I have confirmed that the first notice disappears when replacing the W5W bulb. I ordered the other bulb as I don't have it in stock.

So, lessons learned?

  1. Try to trust the schematics & notices
  2. Even if they're wrong?? (The schematic was somewhat wrong, the OBD error code description was wrong, ...)
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