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Just been spending an hours or two searching the forums, but can't find my problem, though there is plenty of posts related to bulb failures and fast flashing. It only started occurring yesterday, with no obvious initiating factors (no bad weather, major potholes in the road etc, but I did turn the lights on on my way home, which hasn't been necessary for a little while)
Symptoms are:
With side lights and headlights turned off:
When I indicate right, the right indicators flash normally but the front left indicator will also flash at approx. half brightness.
The reverse happens when I indicate left (Left light normal, right at half-brightness).
In all cases the rear indicators work normally
When I turn the sidelights and/or headlights on:
The same happens but the indicators flash at double speed (front and back) and both sides are equal brightness
Apart from the faster flash, the rear indicators work normally
When the indicators are not on, the front sidelights are very very dim
The hazard lights work correctly in all configurations
The following relevant fault codes are tripped:
B2578 H C Right Front Turn Signal Monitor Circuit
B2583 H C Left Front Turn Signal Monitor Circuit
What have I tried/checked so far:
All bulbs seem to be working (none seem to have blown and will light up fully in some configurations
Battery is good and fully charged
Reset fault codes
Disconnected battery and reconnected
Note that it's a 2001 Euro-spec manual targa C5, so the lighting config is slightly different from the US spec.
Any thoughts or inputs would be greatly appreciated
Okay, the DRL sockets are notorious for getting burned/melted/cracked because the OEM bulbs get so hot. This will cause some of the problems you list. The bad news is that it is very difficult to get to the sockets and take a look. A lot of guys remove the headlight assemblies and then replace the corrner reflectors and DRL sockets (add a longer wire splice!) at the same time and upgrade to LEDs. (this will also require a hyperflash harness). While you are there, it's a good time to replace the headlight gears.
Thanks jcgunn and apologies for the late reply.
I've just been crawling around under the front with the lower access panels removed to check all of the bulbs (three per lower light cluster). I couldn't see any damage/corrosion/damaged wires and none of the bulbs were blown. However, I've just replaced all of the bulbs in the lower clusters anyway, as well as the rear side markers and rear indicators. I've not managed to do the front side (wing) lights yet as I can't find the lug nut key to remove the wheel and access it... doh! I've got some nut extractors coming to help remove the offending nut, as would rather do it that way (if possible) rather than hammering an over-sized socket on.
So far no change to the symptoms and I'm not holding out much hope for the front wing lights
Are there any obvious next steps to investigate? Would a basic diagnostic tool help to diagnose, or are there good places to probe with a multi-meter?
You can use your multimeter to do voltage drop checks on the wiring circuit…many YouTube videos about voltage drop testing if you don’t know how to do it…below is how to diagnose your 2 DTC’s.
Hurray - fixed
Thanks C5 Diag for the steer on voltage testing - I looked at a couple of videos and it became apparent that the symptoms I was seeing were likely due to a bad ground somewhere. I started to clean-up the earthing points and found that the forward point on the passenger side (G102) had a bad connection. I've cleaned it up and it seems to be fine now, with all lights working correctly.
I did give the wires a wiggle afterwards and it didn't come back, so hopefully it was just the comb connector. If it returns then I'll need to dig a little further into the wiring, but will keep my fingers crossed that it doesn't.
Best regards,
Bill
PS. I did have a couple of questions about the useful tables that you included in your post...
- What is the first row that's missing from the images?
- Is the first column to the right of the directions 'Yes' and the second one 'No'?
- When it says to install a 'scan tool', does it mean a proper diagnostics tool e.g. Tech2, or does the on-board tool work? I've not got a proper diagnostics tool yet, but maybe that would be a good plan. Will have to search the forums for advice on suitable ones that are available in the UK.
Great !!…yes, left column is yes and right is no on this logic tree…they mean a Tech 2 when they say connect the “scan tool”…you can use a bidirectional scan tool in lieu of the Tech 2…I personally don’t like using these troubleshooting trees especially when it comes to electrical checks…GM has you using resistance checks with an ohmeter when you should be using loaded circuit testing using voltage drop testing…I guess the GM Engineers should have consulted people that actually know how to test electrical circuits.
Both front indicators flash when turning
