Stephen Meredith

I posted here because it has more traffic than tech.

I installed LED tails 2 weeks ago and had no problems. Installed the hyperflash unit last week to fix the signals & no problem. Installed the LED 3rd brake light Friday night and now the "SERVICE TRACTION/ACTIVE HANDLING" error beeps at me every time I drive the car with 2-3 minutes of starting it.

I searched but can't seem to find a solution other than "maybe it needs a resistor". Where might I need the resistor? And what size? Does it need to be spliced into the 12v & ground of the 3rd brake wiring?

Any ideas c5 brethren?

Vetteman Jack

The Tech section has a good amount of traffic - I'm going to move this over there since that is really where it belongs. If you see you do not get the responses you expect, let me know and I will be glad to move it back over to the C5 General section for you. But give it a chance in Tech - lots of good advice is given there on all sorts of C5 issues.

zachaeous

I had a similar problem when I tried to install LED Bulbs only in my taillights. I did not have the LED Taillights assemblies. The way I compensated for it was to install two incandescent bulbs and the two LEDs.

It worked ok then. If it was me I would put a load resistor in the LED brake light circuit and see if it works ok.

neutron82

pull the led lights and make sure none of the wiring is melted... if nothing looks out of the ordinary reinstall the factory lights and see if the issue persists... I had this issue years ago and both inner led tails had melted at the socket and was causing the taillights to go haywire... luckily they were under warranty and after replacing them I haven't had a problem since

Stephen Meredith

Thanks brother

Stephen Meredith

Thanks for the advice guys! I plugged the factory 3rd brake light back in & the problem went away. So I'm guessing the factory one has a load resistor built in.

InfiniteReality

Kinda glad I came across this. I installed LED bulbs right after I got the car (kept OEM 3rd brake light since it's LEDs already) and everything seemed fine. Few months later my "service active handling" error will randomly show on the DIC. Also if I leave TCS on, while going down the road I'll fill it kick in for a second and get 2 messages. I always assumed I need to get a new module when it gets warmer and that it was all connected, but now I'm wondering if this is all because of the LED bulbs. Any idea?

Also I pulled codes on it thru the OBD2 Bluetooth, but comes up clean.

GCG

LEDs in the C5 taillights usually require shunt resistors to avoid code 1295. That's why the popular rear halo LED housings have a built-in resistor in each unit. Take a look at this picture: it's the module inside the aluminum heat sink.


Therefore if the path to ground is open, or the EBCM thinks is open because now you have LEDs, the code will be set and the Service Traction Contron and Active Handling messages will appear. A hyperflash harness will not prevent this from happening, it only prevents turn signal hyperflashing.

You will need to connect a shunt resistor in your tail lights circuit to provide the ground path the EBCM expects to see for those 5 volts

InfiniteReality

Have a bunch of them laying around in different resistances. Should I connect it to the brake or running light positive?

GCG

To the brake light circuit. It should be in parallel with the brake light filament of the rear bulbs.

Attach the resistor to a metal surface to help dissipate the heat

Stephen Meredith

So do I need just one on one brake light? Or one on each brake light?

InfiniteReality

Most definitely. Worth a shot and see if it makes any difference before I buy a rebuilt module.

I think you can get away with just one since they're all on the same circuit, but it may need to be sized accordingly since GCG said each aftermarket LED housing has one on each light. Brings up another point, what size does each aftermarket LED housing have?

Stephen Meredith

I tried using a 50w resistor, the common "led turn signal" resistor with no change.

What I have found now is that the error only happens when I use my left turn signals or hazard button NOT on the right signal, brakes, or normal driving, only when I use the left signal/hazard.

Tsumi

Where did you connect the resistor?

Stephen Meredith

I originally ran it online connected to the brake/turn wire. When nothing happened, I found online a site that showed instructions and said to connect one end to ground and one to the brake/turn wire. So I did that.

I put one on each outer taillight.

I'm not sure what that would have to do with the left turn signal & hazard button causing the problem. I'm more confused now than I was to begin with.

Stephen Meredith

Update: Issue is still there soemtimes but here is what I have found about it.

One of the resistors on the right side came unplugged & made the left turn signal cause the error. plugged back in & turn signals work fine
Hazards not longer flash fast, but still cause the code UNLESS i have my foot on the brake, then no code.

GCG

Very interesting and quite puzzling. It might be invaluable if anybody could measure the built-in shunt resistors that the popular LED Halo tail lights have attached to their back, to compare it to the ones you're using.

Tsumi

My resistors are sitting in a box at the moment, I can get the resistance value easily. They were removed for my project, had no need for them. I'll get values after dinner.

Edit: I read 8 ohms on the resistor.

GCG

Thank you, Tsumi, that's good info!

So Stephen, to emulate what the LED halo taillights do, if you are using just 1 resistor on each side it should be 4 ohms, but double the power rating than the ones used in the LED halo taillights.

What's the value of the 2 resistors you are currently using?

Stephen Meredith

6ohm 50watt each. And I'm using 2. I on each inner taillight.