Rear only stop lights, park lights not working

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.

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
48,363 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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