Cruise Control turns off/will not activate with manual headlamps on.

[lowpost99]

I was cruising the other day and switched on the headlamps, and the cruise control dropped out. Could not turn it back on as long as the headlamps were switched on. Does not happen when lights are automatically on at dusk. I recently got a replacement bulb and receptacle from DDM tuning and installed it about two weeks ago, I noticed it began to hyper-flash the night before I noticed the issue with the cruise control. The bulb replacement was the last electrical thing done to the truck but I can't see what would be causing the issue. Any help greatly appreciated. Electrical and wiring diagrams. Fuse locations, etc. I heard that the hyper-flashing can be fixed by installing the next size fuse in the location for said lights. I'll give that a shot first.

 

[Rocket Man]

Hyper flash can’t be fixed by installing a bigger fuse, and that’s a bad idea anyway. Fuses are rated by what size wiring is in the circuit and a bigger fuse can result in melted wires. You must be installing LED bulbs since DDM specializes in LED and HID? LED bulbs show as burned out bulbs to the BCM since they have a low resistance so for hyper flash you either need a flasher module made for LED or load resistors between ground and positive on the turn signal bulbs. For CC if you have LED in the brake lights you need load resistors there too otherwise the BCM sees no brakes so it won’t engage the CC.

 

[lowpost99]

Hyper flash can’t be fixed by installing a bigger fuse, and that’s a bad idea anyway. Fuses are rated by what size wiring is in the circuit and a bigger fuse can result in melted wires. You must be installing LED bulbs since DDM specializes in LED and HID? LED bulbs show as burned out bulbs to the BCM since they have a low resistance so for hyper flash you either need a flasher module made for LED or load resistors between ground and positive on the turn signal bulbs. For CC if you have LED in the brake lights you need load resistors there too otherwise the BCM sees no brakes so it won’t engage the CC.

Thanks for your reply. Sorry I took so long to reply. The holidays derailed my investigation. So your saying that the HID's on the front headlamps with no load resistors or the LED turn signals with no resistors are causing the BCM to affect the CC? I'm going to check my rear housings that I bought off craigslist for resistors, as I have a combination of LEDs and halogen 3157's in the housings. If I find the resistors, I need to likely test them out to make sure they are still working.

 

[Rocket Man]

Thanks for your reply. Sorry I took so long to reply. The holidays derailed my investigation. So your saying that the HID's on the front headlamps with no load resistors or the LED turn signals with no resistors are causing the BCM to affect the CC? I'm going to check my rear housings that I bought off craigslist for resistors, as I have a combination of LEDs and halogen 3157's in the housings. If I find the resistors, I need to likely test them out to make sure they are still working.

For CC it’s the brake light bulbs that affect it. Mose aftermarket tail lights incorporate load resistors to correct hyper flash. That’s fine for the turn signals. But if there’s LED bulbs in the BRAKE LIGHTS and they don’t have load resistors which nearly none of the aftermarket tail lights do, the BCM will see burned out brake lights or a non functioning brake light switch and will disable CC. You can add a load resistor from the brake light positive wires to ground. I think you have to do both sides, passenger and driver.

 

[lowpost99]

For CC it’s the brake light bulbs that affect it. Mose aftermarket tail lights incorporate load resistors to correct hyper flash. That’s fine for the turn signals. But if there’s LED bulbs in the BRAKE LIGHTS and they don’t have load resistors which nearly none of the aftermarket tail lights do, the BCM will see burned out brake lights or a non functioning brake light switch and will disable CC. You can add a load resistor from the brake light positive wires to ground. I think you have to do both sides, passenger and driver.

Yeah, I pulled it and I think this pic will confirm what your saying... so it looks like the yellow and white turn signal is taken care of with a resistor... which of the 3 wires R, B or white do I splice into or together with a resistor and what kind of resistor do I want to use? That is also the running light which come on automatically at night just like the headlamps do, and that would explain why I lose the CC at dusk.

 

[Rocket Man]

Yeah, I pulled it and I think this pic will confirm what your saying... View attachment 237445 so it looks like the yellow and white turn signal is taken care of with a resistor... which of the 3 wires R, B or white do I splice into or together with a resistor and what kind of resistor do I want to use? That is also the running light which come on automatically at night just like the headlamps do, and that would explain why I lose the CC at dusk.

You want to do the resistor on the truck harness, not the tail light itself. I’m not going to guess on the color, but use a cheap test light to see which wire gets power when you step on the brakes. Splice one end of the resistor into that wire and connect the other end to ground. You can do that right inside the cavity where the tail light mounts- just scrape the paint off a tiny place and screw the wire to the bare metal , and make sure the resistor stays away from the harness wires because it can get hot.

 

[lowpost99]

I added the load resistors and they got hot but still no CC with the running lights on. I'm gonna solder the connections when I get back home. I've got HID HL, LED turn signals in front, could either or these cause the issue?

 

[Rocket Man]

I added the load resistors and they got hot but still no CC with the running lights on. I'm gonna solder the connections when I get back home. I've got HID HL, LED turn signals in front, could either or these cause the issue?

The LEd turn signals could. It's weird but the front turn signals are tied to the rear brake light circuit, I think it's the running light portion of it. I know when I added front LEd turn signals to my 02, the main brake lights wouldn't work without load resistors on the front . I don't remember if I had to add them to the turn signal or marker light wire. I would try swapping the bulbs back to incandescent to see if it resolves the problem.

 

[adventurenali92]

I went through the same thing when I decided to go with LED rear brake and turn signal housings. The first set I bought supposedly had the resistors wired in, according to the sale listing and item description. Plugged them in and nope, no resistors and no cruise control. The aftermarket tails I currently have, have resistors already wired in for brake and turn signal. So LED housings with resistors already setup are out there.

 

[BG1988]

Thanks for your reply. Sorry I took so long to reply. The holidays derailed my investigation. So your saying that the HID's on the front headlamps with no load resistors or the LED turn signals with no resistors are causing the BCM to affect the CC? I'm going to check my rear housings that I bought off craigslist for resistors, as I have a combination of LEDs and halogen 3157's in the housings. If I find the resistors, I need to likely test them out to make sure they are still working.

you can swap the Signal controller to one with it disabled ( GMT900 uses BCM, the GMT800 does not)
something like this
https://www.amazon.com/Novita-LM487-Flasher/dp/B001KS6GIG/ref=asc_df_B001KS6GIG/