Paul Bell

iTrader: (9)

sweetbmxrider

iTrader: (13)

Nice, I would just bypass it. The coil power for the theft deterrent relay is powered by the neutral safety switch though so that will no longer work unless you redo the circuit. I just grounded the yellow/black wire as this is grounded by the theft deterrent module or bcm pending vehicle year and kept the clutch/neutral safety switch.

Spiers

iTrader: (7)

Wow. False alarm. Put a new relay in and nothing changed

Spiers

iTrader: (7)

Alright so here is where I am at:

At the Theft Deterrent Relay, if I use a jumper wire from the purple wire to the yellow wire, it will start every time. This is why we thought it was a bad relay. But I just installed a brand new relay and it hasnt changed my symptoms at all.

Also, if I ground the smaller yellow/black wire, it will start every time. But as soon as I disconnect the ground from it, it will, 8/10 times just click when trying to start.

Also I don't know if this is related or not, but the security light is lit on my gauge cluster. However it has been lit up for 2 years now. But this issue with it starting has never happened until I relocated the battery.

So what the heck does this mean??

Paul Bell

iTrader: (9)

Here's what I'm thinking:

First, there's nothing wrong with your battery re-location work, you did it just fine.

I'm wondering if the problem lies with the body control module. The yellow/black wire is the ground for the theft deterrent relay coil. This wire is grounded within the body control module when it thinks all is a go to start the engine.

The theft deterrent relay's coil gets it's power when you turn the key. It first goes through the neutral safety switch. The coil get's it's ground from the body control module. Missing power from the key start OR the ground from the body control module will prevent this coil from energizing and closing the relay contacts to send power via the purple wire to the starter.

When you disconnected the battery to do the re-location work, everything got powered down and perhaps something in the remote control logic was reset. Do you have the remote control for this car? When you ground the yellow/black wire and start the engine, does the security light go out once it's running?

Spiers

iTrader: (7)

I wish I could tell you. I had sold this car in the past, and the other owner decided to remove the bulb from the circuit board and I've never bothered to mess with that. And yes I do have the remote. I did a lot of work over this winter though, beside relocating the battery. I did some engine mods and extended the wiring in the engine bay in order to tuck it out of plain sight. I also switched out ALL of my interior to ebony, including a new dash.

And just FYI just earlier I changed my 4ga block to frame ground cable to a 1/0 cable.

Spiers

iTrader: (7)

Also I am not that great at reading schematics and testing just yet, but while Big Al was on the phone he had me test the voltage between the purple and yellow wires at the relay, while cranking, and I was reading ~8V. Apparently it's not supposed to be anywhere near that?

Paul Bell

iTrader: (9)

During cranking, the contacts in the theft deterrent relay are closed. This effectively connects the incoming yellow wire to the outgoing purple wire.

While cranking, you should see zero volts between the yellow wire and purple wire.

Spiers

iTrader: (7)

Yea, so I would think that means the relay is bad?? But a new one did the same

96LT1355Z28

iTrader: (2)

Post #27 is a good explination of the cause in LS cars. That is why I did the relay on the purple wire on my car. For some reason when the battery is moved the power to other accesories is reduced including the BCM and TDR.

https://ls1tech.com/forums/drag-raci...st-clicks.html

Paul Bell

iTrader: (9)

Incorrect. This car has good connections as evidenced by it properly starting and running when the OP overrides the ground to the theft deterrent relay provided by the body control module.

The body control module/security system is where the problem lies. Not having the security lamp installed is also hampering diagnosing the problem.

96LT1355Z28

iTrader: (2)

I know it talks about how to do it on shbox's site but it pretty much confuses me. Does anyone know a simple way to delete or bypass the BCM? I don't care about the interior lights dimming, alarm, or RAP. I still need the clutch safety switch to work for NHRA tech though.

I wonder if the problem still exists if the OP puts the battery back up front and reconnects the stock cables?

There's gotta be a reason this starts when people move the batteries, I mean it can't be a coincidence the BCM or anti theft system begins to mess up on nearly every car after the battery is moved!!

If you read through the link I posted from the drag racing section the issue in the LS cars is the terminals size and I guess the actual relays handling capacity. They can put on larger terminals and a bigger relay to fix the issue. I wonder if it's possible to upgrade the TDR to a relay with more power capacity and bigger terminals. I don't know how relays are rated of if it's even possible, just throwing out ideas!

Big Al

iTrader: (1)

Moving the battery is not rocket science. You just need to use the proper size cables and insure you have a good ground path. The starter and alternator are the biggest current devices and they must have a good ground to the battery. Most problems I've found are in this ground path. Run a ground cable directly from the negative terminal of the battery to the engine block. That is the most important path. Use good lugs, I make mine out of copper pipe and solder them on. Those big crimp connectors are great IF you have the proper crimping tool. Use a Vice Grip to crimp it and you're asking for trouble. Bolt them to something like the motor mount bolts that go into the block. Do not attach the ground cable to the Aluminum heads. Then be sure the block and chassis are grounded to each other with flexible ground straps. Like the ones at the bottom of this page:
http://www.wiringproducts.com/contents/en-us/d80.html

Taylor and other wire suppliers have them in all sizes.

I use welding cable for both the power and ground, small block cars are happy with 0, big blocks need 00 especially if they are high compression.

Just do it right and you will have no problems.

Al 95 Z28

Paul Bell

iTrader: (9)

Cut the yellow/black wire. Ground the end going the the theft deterrent relay. Tape up the end going to the body control module.

This takes the body control module and security system out of the circuit while retaining the neutral safety switch. While you haven't solved the mystery of why this is happening, you've bypassed the result and the car will start normally again.

Paul Bell

iTrader: (9)

You haven't told us if you have the remote for this car. I still say the body control module reset itself to a "high security" mode that should be able to be reset with the remote. Having the security lamp functioning would help. The fact that a previous owner pulled the bulb is a clue that the system was not working correctly. Perhaps you simply need to do a remote control re-programming. Powering the car down while doing the battery move job certainly reset the body control module-which may also explain why some people go through this when doing the battery move mod. It's not the battery/cabling that's the problem-it's the body control module programming.

Spiers

iTrader: (7)

The security lamp has been on for the longest time. Before I sold the car I tried replacing the theft deterrant relay, verified the chip in the key, got a new key, even temporarily bypassed that to make sure it wasnt the problem. I eventually gave up since it didn't effect the car beside the annoying light.

My guess is when the other owner decided to put it up for sale he thought it would be easier to sell if he simply (and foolishly) removed the bulb from the cluster. I didnt really care to replace it since it was just an annoyance.

Paul Bell

iTrader: (9)

Originally Posted by Spiers
And yes I do have the remote.

OOPS-missed that. Is it working?

Spiers

iTrader: (7)

Right now I just have a jumper wire at the relay between the yellow and purple wire since the car is still on jackstands being finished. But yes the remote does work just fine.

96LT1355Z28

iTrader: (2)

Spiers, if you ground the yellow/black wire on the TDR what is your voltage while cranking on the purple wire going to the starter. Does is bring it closer to or at 12v vs. letting the BCM ground the yellow/black wire? I'm trying to decide if I could do that and then take out the relay I put inline on the purple wire under the hood. The less wires the better!

sweetbmxrider

iTrader: (13)

Its the key resistor if no one mentioned it. Just ground the yellow/black wire and live with the security light or do a vats bypass. Vats must be disabled in your computer too else the injectors wouldn't pulse.