GMan 3MT

iTrader: (4)

Long shot, but here it goes.

I'm in the final stages of an LS1 swap into my '92 Camaro and need opinions for the next step. I had a donor 2000 Camaro that I stripped. Fuel tank, LS1/T56, rear end, 5th gen brakes, Trans Am seats all swapped over. Once I get it running, I'll be moving to the interior.

The car is currently manual locks, mirrors, & windows. I have a pair of thirdgen doors with power everything that will be stripped and swapped in. I want to use the LS1 steering wheel with radio controls and gauge cluster. I want remote locks. I have the LS1 BCM and a '94-'95 Camaro keyless entry module. The question is, Is it worthwhile to use the LS1 BCM and air bag module or just the ’94-’95 keyless entry and thirdgen airbag and VATS modules?

Let me get a few things out of the way. I'm not looking for the easiest, but am looking for reliability (especially for the remote locks). Yes, I want the airbag to function.
I want the cluster and all the idiot lights to work as much as possible: seat belt, service engine soon, truck ajar, security, airbag, change oil, service vehicle? low oil, check gauges, brake. What causes the service vehicle light to come on anyways?
I’m hoping the skip shift, low trac, abs inop, asr off lights will not be on/functional.

Is the LS1 airbag module much different than the thirdgen module? I know there were advancements in deployment speeds and such at some point, but if the LS1 module is still ‘old school’, then it should deploy in the same circumstances as the thirdgen would. I can splice in the LS1 connector to the thirdgen column and have it function. Now the airbag light would be a problem. The thirdgen diagram shows the module grounding to turn on the light. The LS1 module goes to the star connector, then DLC, then cluster via Class 2 Serial Data (which is magic to me). The only way to have a function airbag light is to use the LS1 module, correct?

Onto the BCM. The BCM has a few nice features that I can live without. RAP, shock sensor, prevents battery drain of interior lights being left on. It does have a nicer chime than the thirdgen buzzer, the exterior light illuminate when unlocked, the horn beeps when locked, and it controls the Security Indicator in the cluster.

I’m not sure how the '94-'95 Keyless entry module functions. Correct me if I’m wrong, but it turns on the interior lights when unlocked for 30 seconds, then turns them off. Is that it? Nothing happens when you lock the doors with the remote? It would be fairly easy to add a relay to turn on the parking lights to illuminate the same as the interior lights. The horn or flashing lights would be nice as an indication that it’s locked, but is livable without. The thirdgen VATS looks to ground the wire from the Security Indicator in the cluster the same way the BCM would.

So ultimately, again correct me if I’m wrong, if I want the airbag light to function, I need to use the LS1 module and BCM. If I’m good with that not working, I’d be best to use the keyless entry module and thirdgen modules.

Drew

iTrader: (58)

Trying to cross-breed the air bag systems sounds like a recipe for a face full of shrapnel. There's a reason every wire for the airbag system is wrapped in yellow warning tape. I wouldn't touch that project with a 10ft pole. If you're bound and determined to have an explosion in your hands, I'd use the entire system from the later car. All of the sensors, the airbag, the coil, the wiring, all of it. I'd mount all the sensors in the same places and in the same manner as they were in the donor car and cross my fingers it'd work if it ever needs to. But then I'd throw all that garbage in the closest dumpster, because having an explosion in my face is not on my to-do list.

The later 4th gen BCM isn't impossible, it's just a bit involved. There's a thread on adapting it here on the forum, but the thread is pretty much total crap. The article on putting the same BCM in a Fiero is better. Having looked at the diagrams for both systems, it pretty much requires rewiring a couple circuits in the fuse box, rewiring the power locks & hatch release, tapping into the interior light dimmer, and modifying the dome light harness. Several wires at the convenience center Chime module are tapped into, etc. It's not for the faint hearted.

If the buzzer in a thirdgen bothered me, the 10 seconds to unplug the chime box, or the 20 seconds to unplug it and plug in the later "Ding-Ding-Ding-Ding-Ding-Ding" instead of the "SCREEEEEEEECH" box, would be about the extent of my efforts.

The early 4th gen box pretty much just does keyless entry. It's about as complicated as an over the counter add-on alarm.

Drew

iTrader: (58)

A few more things...

Converting a manual thirdgen to a power window/mirror/lock thirdgen is EASY. Just plug the wire harness into C238 or the huge power buss above the hood release, screw down the ground wire, and done. I would recommend using the late thirdgen Potter & Brumfield power lock relay, as it's vastly better than the tin can used up until at least 1987. The P&B can be found in 89-92 cars, maybe 88. If using the late 4th gen BCM, the BCM takes the place of the relay anyway...

If you're using the 4th gen VATS, for the LS ECM, the thirdgen VATS module isn't going to do you any good. The signal generated by the thirdgen VATS module is not the same signal the 4th gen BCM generates. Of course the best way to deal with that is to program the EFI to disable VATS and bypass the VATS start enable relay. Or you could keep the thirdgen VATS module and just use it to switch the start enable relay, but I don't see the relay stopping a very sophisticated thief. It's literally just a relay that connects two wires, hiding behind a panel that takes seconds to remove.

AFAIK, the BCM doesn't have anything to do with steering wheel radio controls, the airbag, or any of the dash lights aside from the Security Indicator and the LED for the alarm.

John in RI

iTrader: (167)

Installing the 94-96 Key-less entry is pretty easy. Also nice that it's a "stand alone" set-up. I added this to my Thirdgen ( an 84 ) about 10 years ago and still love the having it as an option.

https://www.thirdgen.org/forums/elec...ess-entry.html

scooter

iTrader: (11)

The 3rd/4th gen steering columns are essentially the same, I am not sure why the 4th gen air bag wouldn't just plug directly into the 3rd gen harness and work. It's not rocket surgery to make an airbag deploy, just a voltage. I wouldn't start cutting anything, but I would stay with the 3rd gen sensors, it is a stand alone system, you could keep the 3rd gen SRS and put in all the 4th gen dash harness stuff if you want. This is not advice though, take it how you want but I take no responsibility.

If I had a car that I wanted keyless entry/alarms, express down windows, RAP and whatnot, I would just buy that stuff separately and put it in, all those things are available new as add on units. I have a complete harness from a 99 Firebird that I plan on putting in my 91GTA, but only since the car had a fire and I need to replace everything anyway. I bought the harness before I bought my Advanced Keys alarm system, and I use the same fob for 2 of my vehicles, and will add in all the others except the "Firebird" since I already spent the money. I like the idea of the GTA staying all "factory GM" when it is reborn, but won't be stock at all. It will be a bastard, 88 Notchback hatch, LSx T56, C4 IRS

GMan 3MT

iTrader: (4)

Are you just against air bags in general or concerned about it not functioning as designed in this case? I don't see how wiring would affect the physical characteristics of the airbag suddenly deploying shrapnel. That flaw (Takata) is there within the airbag itself.

Thanks, I found the one on here. I'll search for the Fiero one.
Honestly it's been so long (2 years) since the car has run, it may have the "ding" box; it's a '92. I'll be bending the tab for the seat belts, so it will only ding when the headlights are left on. Yes, I do always wear my seatbelt when driving and don't need a reminder. The noise is just annoying when the door is open with keys in the ignition when left there intentionally. The diagram doesn't have anything on the internals of the audio alarm, but basically I'll play with it to just have it sound if the headlights are left on.

Good to know. My spare doors are from a '91, just haven't had a chance to see what wiring I saved.
VATS is programmed out of the PCM. I was going to remove the VATS altogether, but still wanted some sort of security. Simplest thing is to do something to disable the starter relay. Since the VATS module does this and can control the security light, may as well leave it in. I plan on another switch inline with the Ignition relay. I agree if someone really wants the car, they'll get it, but may as well make it a touch more difficult for the lesser experienced car thief. Heck, just it being a manual helps.

The physical plug at the top of the column is different. I understand some of Drew's concern. It's going to be more straight forward to leave the rest of the 3G system with just the 4th gen airbag and just lose the airbag light.

I'm really leaning that way, as you say, since it's stand alone. Makes it easier to add or change things in the future when new gizmos and gadgets come along.

Drew

iTrader: (58)

Yes. Airbags in general strike me as a bad idea. That whole thing where first generation airbags deploy so violently that "second generation airbags" was a selling point, then the anti-personnel mine effect of the import airbags... I just don't trust them. I've been in a head-on collision without an airbag, the seat belt did the job fine. Maybe now that I'm more than twice as old, it wouldn't work out the same way, but I'd rather take my chances than hope an airbag from the 90's would save my life. I don't trust them based on age and decay, on top of everything else.

My concern with trying to cross-breed the 3rd and 4th gen airbag wiring, sensors, etc is that I don't know how specifically the various sensors and modules monitor the system. Splicing the wires could result in a change in resistance, and the system could detect something that's not there. Or it could result in a situation where it doesn't sense something it should have. I'm not an engineer, and I don't have intimate knowledge of exactly how the system works, but from all the warning labels, yellow wire wrap, connector assurance locks, self-grounding terminals, etc that I see in the airbag wiring, I wouldn't go cutting it without looking deeply into the subject.

I don't know if the SIR DERM diagnostic features would read a 4th gen airbag correctly, or if it'd trip the SIR warning light, or cause other problems. That's why if I were going to do something like making the 4th gen airbag work in a thirdgen, I'd lift everything out of the 4th gen and drop it in the thirdgen without cutting/splicing any of the wires. This still wouldn't account for any random crazy mathematical differences between the 4th and 3rd gen bodies that might effect the sensor's abilities to detect a crash, but it'd eliminate compatibility issues of the system itself.

Here you go - http://www.fieros.de/en/articles/BCM.html
It's not the best, but it's better than the write-up here. Like most instructions for things that are easy enough to screw up, I'd say read through them a few times until they make sense.

The chime box changed a couple times. They may not all interchange, but at least a couple of them do. Some ding, some buzz. If you just want to get rid of the seatbelt warning, unplugging the retractor on the floor will keep it from buzzing.

If you do the BCM, it has the chime function built in, and it'll replace the chime box anyway. Hence the reason that the BCM can be wired into 4 or 5 circuits right at the Convenience Center.


The door wiring is kind of a pain... On 91's anyway, the harness is all one piece from the switches in the console all the way to the power lock solenoids in the doors. Both the lock and window motor wiring has to be unclipped from the doors, the rubber bellows boots between the doors and jambs have to be popped out (they're taped to the harness), and the whole works has to be fished through the door jambs. Then it's pretty much self contained across the cross-car harness channel at the top of the firewall, the only other harness in there should be the cruise control harness. But anyway...

Again the BCM pretty much re-imagines the power lock harness. Because the way the BCM works, the switches send the signal to the BCM, and the BCM sends the signal back to the lock solenoids. Also since the BCM controls the driver and passenger's doors independently, the wiring has to be split apart for the unlock control, so that the driver's door can be unlocked without unlocking the passenger's.

The BCM does the same thing with the dome lights, door jamb pin switches, and the hatch release. The dome light switch (IP dimmer switch) sends the signal to the BCM, and the BCM turns on the dome lights, instead of the switch grounding the circuit on it's own.

The pin switches each send a signal to the BCM, and the BCM uses that signal to trip the dome lights, or to know when one or the other door is opened, etc.

For the hatch release, the switch in the dash signals the BCM, the BCM then signals the relay.

This is primarily so the BCM can do it's thing with signals from the key fob.

The thirdgen VATS module does two things... It looks at the key, and if the resistance is right, it trips the relay, basically connecting the tan/wht and yellow starter circuit wires. This is really easy to bypass since it's something anyone can jumper right at the relay. That's why GM put the relay behind a rubber sticker to hide it. Most people are going to figure out how to bypass this easily if they don't already know.

The tougher part of thirdgen VATS is that it generates a signal that it sends to the ECM. The ECM looks for the signal and if it's not there, it disables the fuel injectors. That's where reprogramming the PROM to bypass vats comes in.

The BCM does the same things as the thirdgen module, except the signal it sends to the PCM is a different frequency or wave, whatever... The BCM and 3G Vats module use the same keys and vats resistor values. But it's unclear if the BCM uses the VATS key for anything beyond the basic VATS functions. IDK if the alarm functions of the BCM care about the VATS value, or if not receiving a VATS signal from the correct key will cause the BCM to go into error mode, etc. Since your PCM isn't looking for VATS, you should be able to use the key value that matches your BCM, and use the BCM to trip the relay, but I don't know that the relay function is worth messing with since it's so easy to bypass. Maybe move the relay to the back of the dash or something.