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Found and fixed problem with Rear Light Failure Message! Posted by scott47 [Email]  (#119) [Profile/Gallery]
(more from scott47) on Wed, 24 Jan 2018 08:57:57
In Reply to: Need help with Rear Light Failure message, scott47 [Profile/Gallery]
, Fri, 15 Dec 2017 20:17:21
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Sorry so long, but I'm going to list everything I tried just in case it might help someone else. Plus, if I have this problem again in the future, hopefully, I can remember what not to do :-)
I finally found the problem that was causing the "rear light failure" message on my 2005 Saab 9-5 Sedan! It turns out there was one problem, which when I tried to fix it, I created another problem. Then after I fixed the first problem, the message still appeared because of the second problem. How's that for confusing??
The real, first problem, was a bulb. It lit up like all the others and the resistance I measured directly on the bulb was very close to the others. The problem was the resistance changed when it was in the bulb socket and I measured the resistance from the where the wires plug into the bulb carrier. I tried several different bulb carriers and that one bulb had a different resistance when it was in any of the carriers vs. when I measured the resistance directly. There must have been a problem on the bulb, in the area where contact with the carrier was made although I couldn't see anything, or measure the difference outside of the carrier. The solution was to throw that bulb away and start over with a new bulb.
Note to self: When checking the bulbs, be sure to measure the resistance at the plug on the bulb carrier instead of the bulbs themselves!
The second problem was one I created by playing with a cloned Tech 2. I was trying to find the reason the rear light failure message was showing up. When doing that I changed the Rear Bulb Configuration from "Rest Of The World" to "US". I thought this made sense at the time, but now that I've been able to test with a working TWICE unit, having this set to the US will cause the rear light failure message every time (at least that is what happens on my car).
Note to self: Don't play around with the Tech 2, it's isn't as forgiving as a PC or phone!
Here are some of the things I've tried while searching for this issue:
1. Check that the bulbs all light up as they're supposed to.
a. 5 x Center Brake Light (#2825)
b. 2 x License Plate Light (#2825)
c. 2 x Reverse Lights (#7506)
d. 1 x Driver's Side Rear Fog Light (#7506)
e. 1 x Passenger's Side Rear Fog Light (#7506) – On my car, the lead to this bulb is cut so it will not ever work even though there was a bulb in the socket. Frustrating if you don't know that that bulb is not ever going to work. Check to be sure if your car is the same way or not.
f. 2 x Rear Turn Signal Bulbs (#7507)
g. 2 x Brake Light Bulbs (#7528)
h. 2 x Tail Light Bulbs (#7528)
2. Checked the resistance on all the bulbs to verify they are close to the same. I did this by holding the multi-meter leads directly to the bulb.
3. Checked, cleaned and roughed up all of the bulb sockets, even though they all looked to be in great shape.
4. Played around with the Tech 2 and changed the Rear Bulb Configuration. Learned later that this is not the right change to make.
5. Checked the resistance of the bulbs by connecting the multimeter to the bulb carrier. At this point, I found a problem but the rear light failure message still appeared.
6. Replaced all of the bulbs with brand new bulbs from RMEuropean.
7. Replaced all of the bulbs with brand new bulbs bought locally from the same store, at the same time.
8. Went to the salvage yard and found several bulb carriers and the trunk lid wiring harness which appeared to be in good shape. I tried switching these into my car but nothing changed.
9. Pulled out the TWICE unit and cleaned its contacts even though they looked fine.
10. Bought a second TWICE unit from eBay. This did not come with a key or chip since I was only trying to figure out if the TWICE unit was at fault and I didn't want to spend more $$ than I already had.
11. Hooked up the twice unit and ignored the messages about the key not matching and the ignition being disabled. Turned on the lights and no messages appeared. Removed one of the tail light bulbs, turned the lights back on and the message appeared. Now we were getting somewhere!
12. Used the Tech 2 to step through the TWICE settings that could be changed on the working eBay unit. Looked for the items that were different than my original TWICE and there was only one…the Rear Bulb Configuration. I changed that on my TWICE to match the eBay unit (from US to Rest Of The World) and everything was back to normal.
Months later and many $$ wasted but at least I am not annoyed by that message every single time I start my car. Plus, more importantly, I won't have any problems when I take my car in for its required emissions test!
If you are also having this issue, good luck! Please reach out to me if there is something I might be able to help with.
, Fri, 15 Dec 2017 20:17:21, Wed, 24 Jan 2018 08:57:57 <-- Viewing This Message, Sun, 17 Dec 2017 07:00:01
, Sun, 17 Dec 2017 14:50:59, Sat, 16 Dec 2017 08:44:14, Sat, 16 Dec 2017 07:03:53
, Sat, 16 Dec 2017 06:11:01
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