Rear only stop lights, park lights not working

Tiny
ROB CUNNINGHAM
  • MEMBER
  • 2008 FORD F-250
  • 6.4L
  • V8
  • TURBO
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
Back of cab 3rd brake light and all lamps forward normal. Rear turn signals normal. Replaced LED bulbs no fix. Ckd harness grnd at left rear frame good. Replaced brake switch at pedal. Replaced multifunction switch at column. Ckd 2 under hood brake light fuses position 12, 13 good. Ckd park lights fuse position 22 at passenger kick panel (smart junction box) good. Ckd main harness connector under hood LH side for tightness. Wiggle, unplug plug back in all connectors to multifunction switch. Most interesting symptom tail bulb will flash on then back off at brake pedal release. Guessing if SJB or GEM needed reprogrammed other intermittent interior symptoms would exist but not the case. All interior cluster and dash features ok.
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Sunday, August 4th, 2019 AT 11:39 AM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,544 POSTS
Hello,

It could be the SJB, but there is also a taillight relay we should check. Here is a guide to help with the running light wiring diagrams so you can see how the system works with the relay location as well below:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Look for power at fuse # f22 Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
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Thursday, August 8th, 2019 AT 10:51 AM
Tiny
ROB CUNNINGHAM
  • MEMBER
  • 2 POSTS
Thank you very much. If the issue remains corrected it seemed to be a problem with incorrect LED bulb polarity installation.
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Friday, August 9th, 2019 AT 3:34 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,544 POSTS
So the problem is fixed or?
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Friday, August 9th, 2019 AT 12:38 PM

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