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Discussion Starter #1
Hi all, I’ve been trying to work out why my 3rd brake light suddenly stopped working when every other light at the rear still works fine ??? Just came across a post with the same issue and was able to download the rear SAM wiring diagram which helped the other member but, I can’t make sense of it ? All I know is when I stick my multi meter to the stripped power wire it shows a voltage of 0.05v s so it’s as if the power is being cut off somehow ?? Any help would be much appreciated as this issue has been driving me nuts for months now AND my boot is still stripped out whilst I fix it ! PS. All fuse s are ok and I’ve replaced certain relays but no joy ! Hope for some help, many thanks !
 

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Dallas, Texas
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Hi all, I’ve been trying to work out why my 3rd brake light suddenly stopped working when every other light at the rear still works fine ??? Just came across a post with the same issue and was able to download the rear SAM wiring diagram which helped the other member but, I can’t make sense of it ? All I know is when I stick my multi meter to the stripped power wire it shows a voltage of 0.05v s so it’s as if the power is being cut off somehow ?? Any help would be much appreciated as this issue has been driving me nuts for months now AND my boot is still stripped out whilst I fix it ! PS. All fuse s are ok and I’ve replaced certain relays but no joy ! Hope for some help, many thanks !
You need to finish setting up your profile. Year, model, location?

What color is wire you are probing?
 

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Discussion Starter #5
It’s the stripped wire from pin 22 seems to have 0.05 volts instead of 12-14...... so basically not enough power to the 3rd brake light.... tried another SAM but same issue.....
 

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It’s the stripped wire from pin 22 seems to have 0.05 volts instead of 12-14...... so basically not enough power to the 3rd brake light.... tried another SAM but same issue.....
Do you have scanner that can access rear SAM?

If SAM detects open or short circuit it shuts down output to offending component. You need to find out what is it. With key off and out of ignition disconnect connector to the SAM and measure resistance between pin 22 and ground. Since third brake light is LED observe polarity.
 

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Discussion Starter #7
Don’t have a Scanner ? I have an ancel diagnostic kit which tells me rear Sam/ open or short circuit to 3rd light. Component being a relay or something ? I will disconnect the SAM tomorrow and check what you have advised, thanks
 

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Discussion Starter #8
Ok so yes I do have a scanner then, sorry was being a bit thick. Infact I will take a photo of the display tomorrow and post it up here, thanks
 

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Discussion Starter #9
Had to use my multi meter as nowhere local has a test light in stock ! Anyway. Checked earth for continuity at pin 22 and meter beeped. Then with ignition on, pedal depressed still good earth and + showing 11.96v. So can anyone work out what maybe at fault from this ?
 

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Discussion Starter #10
Had to use my multi meter as nowhere local has a test light in stock ! Anyway. Checked earth for continuity at pin 22 and meter beeped. Then with ignition on, pedal depressed still good earth and + showing 11.96v. So can anyone work out what maybe at fault from this ?
 

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Discussion Starter #15
Lol so can anyone come to a conclusion as to what is causing the open/ short circuit ? Which component ?
 

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Discussion Starter #18
Ok thanks. Tho from what I’ve already tested it seems the earth is ok, just voltage seems to be cut..... when I connect my meter to that stripped wire that was connected to the LED plug with pedal depressed the voltage is around 11v but straight away just drops to 0.02- 0.05v so it’s being drained/ cut off somewhere ??
 

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Ok thanks. Tho from what I’ve already tested it seems the earth is ok, just voltage seems to be cut..... when I connect my meter to that stripped wire that was connected to the LED plug with pedal depressed the voltage is around 11v but straight away just drops to 0.02- 0.05v so it’s being drained/ cut off somewhere ??
What you mean was? If SAM detects open circuit it shuts it off.
 
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