Brake lights are semi functional?

Tiny
SEAN D. ELDER
  • MEMBER
  • 2009 NISSAN XTERRA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 154,000 MILES
I’ve recently changed the brake lights on my vehicle; the issue is that they work as hazards, but not actual brake lights. There’s continuity on all the breakers the socket itself, and my battery is running at a bit low. Low enough to take a few seconds to start, but fine otherwise. Is there any other diagnostic criteria that I’m missing?
Thursday, August 10th, 2023 AT 4:31 PM

18 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,348 POSTS
Do you have power at the fuse # 20 on the right side of the fuse panel?

This guide can help:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

If so, please test through the brake light switch, here is the location in the images below, also please go over this guide as well:

https://www.2carpros.com/articles/brake-lights-not-working

Here are the brake light wiring diagrams so you can see how the system works. Check out the images (below). Please let us know what happens.

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Friday, August 11th, 2023 AT 10:57 AM
Tiny
SEAN D. ELDER
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I haven’t tested the brake switch, and I believe that may be where the problem lies. Worst case scenario I will be replacing it as soon as possible.
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Friday, August 11th, 2023 AT 1:01 PM
Tiny
KEN L
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Sounds good please let us know.
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Saturday, August 12th, 2023 AT 9:01 AM
Tiny
SEAN D. ELDER
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  • 12 POSTS
So, after replacing the old switch, the brake lights still aren’t working. I tested continuity on the connection to the switch and found that the connectors top female ports do not have continuity. Does this mean I need to change out the wire harness?
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Monday, August 14th, 2023 AT 4:53 PM
Tiny
SEAN D. ELDER
  • MEMBER
  • 12 POSTS
Another note. I charged the battery, just to make sure that there wasn’t a low power issue.
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Monday, August 14th, 2023 AT 4:58 PM
Tiny
KEN L
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On the brake light switch do you have power at the red/blk wire?

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Test with the key on.
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Tuesday, August 15th, 2023 AT 8:40 AM
Tiny
SEAN D. ELDER
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Don’t have a probe like that, I have a CL120. But I’m getting tone indicators from all four points.
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Tuesday, August 15th, 2023 AT 8:48 AM
Tiny
SEAN D. ELDER
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I’m changing out the relay for the brakes. Hopefully this is the solution.
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Tuesday, August 15th, 2023 AT 11:01 AM
Tiny
KEN L
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Is fuse #20 good?
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Wednesday, August 16th, 2023 AT 10:54 AM
Tiny
SEAN D. ELDER
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Yes, I've tested all of the fuses for continuity, and they are all giving tone.
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Thursday, August 17th, 2023 AT 11:31 AM
Tiny
SEAN D. ELDER
  • MEMBER
  • 12 POSTS
As of this post, here is what’s been done to remedy this situation. Testing tool used: Klein Tools CL120 Voltmeter.
1. Changed bulbs, and also inspected sockets, and tested for continuity: there is tone.
2. Changed and re-inspected fuses: tone from sockets and also new fuses.
3. Replaced brake light switch under dash above the brake pedal; tested socket continuity: there is tone.
4. Changed all but one brake/rear light relay (the sun was setting.) Unsure of how to test for continuity in this case.
5. Checked the engine fuses related to the brake or rear lights; no replacements made: there is tone.
Once again, the odd thing is that the top rear brake light bar is functioning, but not the two on the rear; And yet the hazards, reverse, and turn signal lights are all functional.
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Thursday, August 17th, 2023 AT 11:54 AM
Tiny
KEN L
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With the key on and the brake pedal depressed do you have power at the yellow wire from the brake light switch?
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Friday, August 18th, 2023 AT 9:46 AM
Tiny
SEAN D. ELDER
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Yes, I tested both fuse and cable with the key set to on. There is tone on both.
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Sunday, August 20th, 2023 AT 8:16 AM
Tiny
KEN L
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Okay, now with the brake pedal depressed check the yellow and blue wires back at the brake lights bulbs, are the bulbs good?
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Monday, August 21st, 2023 AT 9:19 AM
Tiny
SEAN D. ELDER
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With the key set to on, and the brake depressed, the socket is giving tone. The wires are black and green to the brake light socket.
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Wednesday, August 23rd, 2023 AT 8:05 AM
Tiny
SEAN D. ELDER
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Still the brake lights don’t work when brake is depressed.
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Wednesday, August 23rd, 2023 AT 8:10 AM
Tiny
KEN L
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Okay, it sounds like the bulb ground is bad (black wire). I would use this guide to help check the bulb ground.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

You will need to extend the lead on the tester or use a voltmeter.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go over these guides and get back to us.
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Thursday, August 24th, 2023 AT 10:51 AM
Tiny
SEAN D. ELDER
  • MEMBER
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Okay, so something interesting has happened. I was testing the ground for the taillights and noticed that one of the lights on the back of the vehicle switched to functioning as a brake light when the brake is depressed. So now the top bar and the passenger side bottom light is functioning as a brake light. The actual brake lights are still only functional as turn and hazard lights. Does this mean I need to change the connectors?
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Wednesday, August 30th, 2023 AT 6:48 AM

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