Anyone heard of this

[Shawnbonay]

Ok I have 03 silverado I jst bought a 5.3 bored to 5.7 with forged rods and pistons from summit. Anyways I put a stage 2 centrifugal cam cuz I have small blower and bought afr heads.anyways I paid someone to tune it and every time we started it .it would go in to reduce power mode loss communication throttle body. I have nick Williams 103 throttle body with that damn xlink. He thought it was xlink but we figured out that if we turned head lights off it wouldn't do this. truck ran fine b4 new engine I do have aftermarket led headlights never heard of this anyone ever been in situation and fixed it please please let me know thanks

[blindsquirrel]

https://forum.hptuners.com/showthread.php?26427

[SiriusC1024]

You're missing a ground then. It could be any of them. Pull up electrical schematics for your truck. Sometime you can find ground locations listed on a forum like LS1Tech. Find them and clean them. Verify with the vehicle running using a meter set to voltage instead of resistance. Voltage between battery ground and a good ground will be near zero (low mV). The TAC module is a delicate flower that is susceptible to mV fluctuations. Using resistance won't show saturated grounds. A saturated ground is why your headlights are having an effect.

[Shawnbonay]

thanks i will do this

[Shawnbonay]

Well still doing this if I unplug driver side low beam it good but today will trying stuff unplug high beam and lose all power I can here the throttle body when I plug it in and out weird losing on this one

[SiriusC1024]

Aftermarket LED's cause a lot of noise. Run a dedicated power supply straight off the battery through a relay to the headlights. That or remove them.

[Shawnbonay]

I'm going to put original back in and see what happens BRB

[Shawnbonay]

Well can't find originals but if I remove ether side truck dies and I removed leds any if I turn brights on it kills it I tryed different tac yesterday still the same I got grounded wires going every were I'm at a lost for ideas I do have another pcm I can swap in there but I jst did a motor swap 4 months ago every thing was fine then

[SiriusC1024]

It's not the PCM. It's a wiring issue that has to do with the headlights. The grounds for those are on the core support. Those grounds can also affect the relays inside the fuse box. If you were using a meter it would help a lot. Some LED drivers are a switched power supply. Usually they're chinese junk that isn't in spec and make a lot of line noise.

[Shawnbonay]

I have one jst never really used one my ground is good on support beam but how should I check with meter?

[Shawnbonay]

And jst noticed on passenger side I keep a funnel guess over the years wires are soaked with oil trans fluid and things like that not sure if this will hurt wires but probably can't help

[SiriusC1024]

I have one jst never really used one my ground is good on support beam but how should I check with meter?

Post #3 has instructions.

[Shawnbonay]

Well I went through all wires nothing bad that I can see. wires are hard were oil got on them so I jst made a ground to high beam ground and everything is working like it should didn't find problem but it works now

[SiriusC1024]

Good. So that probably means the ground on the core support is questionable.
headlight ground.png

[Shawnbonay]

Yea probably it looks oh and I took it off and grinding to fresh metal but good be bad somewhere honestly probably more then one ground my lights had a lit flicker this morning. But I appreciate your help thank you