LED brake lights

FRW · October 3, 2003

Wanted to throw something out for discussion. A few month ago the CC on my 03 Tahoe quit working. After checking the fuses and having a CC module replaced I still had no CC. Well I took the truck back in to Chevy and left it for 4 days(there are other nagging electrical problems which they couldn't duplicate and therefore did not fix). Well today they called to tell me they had found the problem. They say it is because I installed LED brake lights and that the lower amperage pull of the lights srcewed up the CC controls. They are charging me $460 for this insight because the bulbs are not OEM. Has anyone else heard of this? Nowhere on this site or any other GM related site have I seen this discussed as a problem. I have seen no service bulletins to this effect, nor have I seen any disclaimers on any of the site of the manufacturers or resellers of these lights about this problem. I would think that if this was true that over the course of the 4+ years that the NBS trucks had been on the market that I would not be the first person to run into problem and it would have been discussed somewhere.

Any information would be greatly appreciated. I would like to call GM on this and get this at least partly covered under warranty if possible.

Tree_Hugger · October 3, 2003

This has been reported on www.chevyavalanchefanclub.com

The problem is that the Cruise Control detects Brake usage, by sampling to see if the brake lights are on, which it detects by the resistance in the brake light circuit. The LEDs have a lot less resistance than the stock bulb.

A resistor in series with the LED is needed to cure the problem. This won't cure the problem with your dealer....

The dealer has spent time and money diagnosing a problem, I can see why they want paying. Neither they or GM caused the problem...

HTH.

03Bluerado · October 3, 2003

They say it is because I installed LED brake lights and that the lower amperage pull of the lights srcewed up the CC controls. They are charging me $460 for this insight because the bulbs are not OEM.

I'm calling bulls**t on this!!! You tell your dealer try again jack! First off, in my understanding of this (and I MAY be wrong) the 03's have NO cruise control s**t to break! The 03 and up full size GM vehicles have the electronic throttle control, the only difference between a truck that has cruise from the factory and one that doesnt is the turn signal stalk! The computer tells the stupid elec. throttle to move, and when you hit that cuise button it tells it to stay, or accelerate or slow down, etc!

I know this for a fact as I clued in my dealer when my cruise quit working when my 03 was 2 days old! My problem was a s**tty clutch cancel switch (5 speed truck) I told the dealer that was the only thing it could be, and it was, the computer handles the rest, basically there IS NO cruise components, thats one of the reasons GM went to the ETC setup, they said it made the CC "MORE ROBUST" !

What a crock of s**t, LED lights, how about this GM, I pull my 16 ft trailer that I converted ALL the lights on to LED's, and gee I have no problems! In most cases, the only adverse effect the LED's bulbs you put in would be making the blinkers go fast, cause they think the bulb is burned out because of the low draw. People have remidied this with a resistor I think.

Electrical is my weak point for sure, but I think your dealer is full is s**t!

01 Suburban LS · October 3, 2003

I think I waould have to call B.S. on that explaination unless other people have heard the same thing as well. As far as I knoe the cruise control de-activated at the brake switch. Thats why there are a handfull of wires coming out of it to go to various contols.

Come to think of it, on my girlfriends Suburban, the white wire that went to the brake lights had been cut, and the brake lights did not work at all, but the cruise contol would still work normally.

Tree_Hugger · October 3, 2003

http://www.chevyavalanchefanclub.com/cafcn...g81114#msg81114

http://www.chevyavalanchefanclub.com/cafcn...g59406#msg59406

You have to buy the LEDs labelled 'for CHEVY', which have the balancing resistor built in....

seadoons · October 3, 2003

I would have to disagree that the new cruise controls don't have any type of device to them and that all they do is lock the gas pedal in the same place. What happens when the truck goes to climb a hill? With the pedal in the same place, it is going to slow down. It has to be able to regulate the pedal position in order to maintain the set speed.

speedshifter · October 3, 2003

01 Suburban LS,

I have a '97 Yukon and the same thing happened to me. The brake lights didn't work, but the CC did. It turned out to be the brake switch. I think that the newer 03s might use a newer system.

tboat · October 4, 2003

Sounds like crapola to me. I bought a set of Putco bed rails with the LED lights in the ends. When I was pulling wires for the right side, I broke the wire that had the resistor in it. I went ahead and wired them direct and they work fine. No problems with any other lights or devices.

asepgrad98 · October 4, 2003

Looks like the dealer could be right...

for 03 tahoe:

The PCM disengages the cruise control operation based on the information received from the TAC module. The TAC module monitors the signal circuits of the following switches:

The On/Off switch

The TCC/brake switch

The stop lamp switch

The TCC brake switch and the stop lamp switch are incorporated into an assembly and are mounted to the brake pedal bracket. Pressing the brake pedal while the cruise control is engaged will disengaged the cruise control system. The TAC module monitors the stop lamp switch signal circuit and the PCM monitors the TCC brake switch/cruise control release signal circuit. When the brake pedal is pressed, the normally closed TCC brake switch opens and the normally open stoplamp switch closes. The TAC module detects a high signal voltage on the stop lamp switch signal circuit and the PCM detects a low signal voltage on the TCC brake switch/cruise control release signal circuit. The TAC module sends a universal asynchronous receiver transmitter (UART) message to the PCM indicating the status of the stop lamp switch. The cruise control system will disengage when the cruise control On/Off switch is turned OFF. The vehicle speed stored in the memory of the PCM will be erased when the cruise control On/Off switch is turned OFF, or the ignition switch is turned OFF.

The cruise control system will disengage when the PCM detects that the driver has the accelerator pedal override active for approximately 60 seconds.

When the cruise control system is disengaged, the PCM sends a class 2 message to the IPC in order to deactivate the cruise control indicator.

BlackSilver · October 4, 2003

With the pedal in the same place, it is going to slow down. It has to be able to regulate the pedal position in order to maintain the set speed.

Not true. All '03s and many earlier (my '01 for example) models have a "fly by wire" throttle setup. The pedal doesn't pull a cable to open your throttle plate anymore, but sends an electrical position signal to the ecm and eventually on down the line to a servo at the throttle body. CC mimics this signal, and the throttle pedal is completely stationary. In point of fact, when you remove your foot from the pedal after you engage CC, the pedal returns to the normal "idle" position and doesn't move.

Sunuvagun, you learn something new every day, huh!

duck slayer · October 4, 2003

So if you put in the original factory brake lights does the cruise control start to work? Should be an easy way to troubleshoot the problem.

FRW · October 5, 2003

So if you put in the original factory brake lights does the cruise control start to work? Should be an easy way to troubleshoot the problem

Haven't had a chance to check that yet so I can't answer that. However, I agree with your assessment of how easy and might I say cheap that checking the brake light bulbs would have been. Instead they replaced the TAC module to no avail then spent 4 days and $460 of my money to discover the problem. They supposedly drove the truck a lot 3 weeks ago while trying to diagnose the ABS problem that they never fixed, but never noticed the difference in the way the LED bulbs made the turn signals work. I call that incompetence. Even my wife and neighbor noticed that for gawd sakes.