Hey All! I have the dreaded rear light issue. I have tried cleaning tge contacts on the plug and housing. Ive tried the ground wire bypass but im not sure if im doing it right. I split the ground wire before the plug, then connect a new wire to that. Then run a wire and connect it to the (what i think) is the ground rail on the unit. Can someone advise if im using the correct ground pin as per photo. Im pulling my hair out!! Please see attached photo if my housing and the rail im using.

Rory.

You have not yet told us what this rear light problem is.

Sorry, i switch the lights on, they flash twice and then get a bulb error on my dash and lights go off

Is the other bulb in the holder working correctly, if your yellow arrow point to what il call pin 1 then pin 3 also looks like a earth connection by the circuit layout 

no the other bulb isnt working either 😞 ok so does that mean i need to geound to both of them?

Check the bulb holder yourself as I’m working of a photo but yes they should both have good earths if that’s how the system is intended. This will because your cars computer will be working from resistance readings to determine if a bulb is blown or not so if it’s using one earth instead of two then the readings might be to high, so when the ecu detects a possible blown bulb it cuts the voltage to it, hence why it tries again when you restart the engine 

Why this may seem strange behaviour from the computer it’s because depending on spec level and model some cars then use a alternative bulb as a emergency tail light 

12 hours ago, Sid2020 said:

Check the bulb holder yourself as I’m working of a photo but yes they should both have good earths if that’s how the system is intended. This will because your cars computer will be working from resistance readings to determine if a bulb is blown or not so if it’s using one earth instead of two then the readings might be to high, so when the ecu detects a possible blown bulb it cuts the voltage to it, hence why it tries again when you restart the engine 

Ive had a look at the wires from the plug. see photo attached. 1. Brown, 2. Blue, 3. Blue and 4. black and white, but the black and white is basically redundant as there is no pin in the connecter or relative rail

So the black and white wire going into the plug doesn’t have a contact connector  inside the plug and the bulb holder has no pin either, never seen thing that’s the case and would suggest it it possible it’s corroded and arc’d to the point there missing as the wire would need the connector on the end to hold it in the plug, could strip back the wire and jump a lead from the wire the the track on the bulb holder and see if that solves your problem 

there is no track for the black and white wire in the bulb holder lol

So pin 1 is a earth and pins 2 and 3 are live feeds for the bulbs and missing pin 4 is redundant on this model of car, have you check that your getting a feed to each bulb and a continuity check from the earth track to a ground on vehicle chassis