Brake switch for Gen IV LMG 5.3
 

My swap is using a 2008 5.3 from a Tahoe. I've read some posts about using a 4 connector brake light switch (needing 12v normally on and off when brakes applied) for Gen III swaps. Is this going to be the same for the Gen IV?

Re: Brake switch for Gen IV LMG 5.3
 

No. For a GenIV swap you just use the original switch and hook one wire to the cold side of the switch so the ECM sees 12v when the brakes are depressed.

Re: Brake switch for Gen IV LMG 5.3
 

Cool. Good to know. Thanks.

Re: Brake switch for Gen IV LMG 5.3
 

Ok so I read this thread and decided to check.
I have a 2008 gen IV 4.8/4L60E.
I have my brake wire Connected to 12volts until the brake is pressed. I am using the gm cruise style brake switch. I check with my scanner and it is correct so for fun I connected it like above ls1nova71 indicated. It read brake pedal “yes” when the brake was not pressed.

We want the scanner to show “no” when pedal not pressed and “yes” when pedal pressed correct?

Re: Brake switch for Gen IV LMG 5.3
 

Gen IVs are backward of GenIIIs so you shouldn't need that switch. Is it working right connected that way? I wouldn't think it would work? Also, what kind of scanner are you using? Usually they will say "applied" and "released" for brake pedal input.

Re: Brake switch for Gen IV LMG 5.3
 

I am using hptuners and logging brake pedal applied yes /no

Re: Brake switch for Gen IV LMG 5.3
 

Would this matter if I didn’t have actual taillights in the truck yet?
Hell the truck doesn’t have any exterior lights.

Re: Brake switch for Gen IV LMG 5.3
 

Following!

Re: Brake switch for Gen IV LMG 5.3
 

I just looked at the schematic for a 2012 Tahoe, and it does show a couple of wires that could go to the brake switch like you seem to have, but I don't think they are necessary in a swap. Do you have the NC set of contacts wired to X3 pins 12 and 13? Pretty sure the only one you need on a GenIV is X5 pin 6 (light blue) which needs 12 when the brakes are applied.

Re: Brake switch for Gen IV LMG 5.3
 

This is how I wired my swap

http://lt1swap.com/E38%20ECM%20Connector%20Pinouts.htm
It shows J1 of X1 pin 9. It’s reads “12v+ hot with brakes applied. Open when NOT on the brakes.”

But that contradicts what HP tuners shows when I tested it. I am a little confused.

Re: Brake switch for Gen IV LMG 5.3
 

This is incorrect.

You need to run everything on the Normally Open side of the switch, so you only get 12v when the brake is pressed.

I assume in your picture that the light blue wire by itself is the one going to the ecm, if so that needs to get tied into the other wires on the other side of the switch.

Re: Brake switch for Gen IV LMG 5.3
 

I agree but when scanning the brake pedal applied yes or no
Wired this way in the picture scans correctly.
That’s the reason for my posts.
I am going to check it with the brake lights actually installed down the road.

Re: Brake switch for Gen IV LMG 5.3
 

Hey guys,
I was able to get to the point of starting the truck and putting it into gear while up on jack stands. While I was checking my rear brakes. I put the truck in drive and while idling I stepped on the brake pretty firm and the engine almost died like the converter was locked.
I tried a few times and it feels like the converter is definitely staying locked. The first thing I thought of was this tread.
I did wire it the way everyone said it should be, it is getting 12v when brakes are applied.
What to check or do????

Re: Brake switch for Gen IV LMG 5.3
 

You can kind of disregard what I said in post 9, my dumb ass was looking at BCM connectors, so sorry about that. I checked it again, and it definitely shows the ECM needing power at X1 pin 9 when the brakes are applied. Not sure why your HPTuners is showing the brake on/off signal backwards though. Have you tried actually hooking up the brake lights to see if that changes anything? Also, what pins do you have the other wires on the brake switch hooked up to?

Re: Brake switch for Gen IV LMG 5.3
 

X1 pin 9 0.5 L-BU/WH 6311 Brake Switch Signal (goes to underhood fuse block P3, wire also goes to TCM, both hook to tcc brake switch at brake pedal, 12v+ hot with brakes applied. Open when NOT on the brakes.)
and 6311 0.5 L-BU/WH to TCM plug.

I do not have any brake lights connected. I will have to wire in a light bulb and see if that works.

I currently have the stock brake switch installed and wired like:
Orange 12v one side of switch

Other side of switch=
White- Brake light feed
Brown- to remote start brake pedal signal
Blue- to PCM/TCM brake light trigger pin 9