choosing correct immobilizer

I've been searching for hours on Google and forums and can't quite find the answer I'm looking for. I'm finding a lot of great information on immobilizer types but am still confused!

I'm installing a remote start on my girlfriend’s 05 Chevy cobalt. The system I'm buying is a Avital 4103LXL. I want to use the keyless entry and trunk functions on that system as well (not use the factory fob at all). I was planning on using the PLJX immobilizer to bypass the passlock. When I look at the description of the PLJX, it says it disables the passlock only, while the XK09 has other features like "door unlock/lock control", etc...

Do I really need the XK09 if I want to use the 4103's fob to lock/unlock the doors, pop the trunk, etc, or can I use the PLJX and just wire from the 4103 unit to the specific wires on the car for functions like unlock and lock?

I don't want to buy the PLJX and not be able to use the new fob to unlock/lock the doors. I also don't want to spend the extra money for the features of the XK09 and have to buy a programmer if I don't need to.

I mean what is the advantage to using the XK09 over the PLJX besides maybe less wiring?

Sorry, I'm pretty familiar with working on car electrical systems, reading wire diagrams, and I have access to Mitchell OnDemand so I have all the wiring diagrams for that vehicle, I just never installed a remote start before.

On a side note, the car already has an aftermarket remote start (doesn’t work anymore) so it must have an immobilizer installed I just don't know what type. It really never worked correctly (door lock and unlock functions) and best buy won’t fix it as it was installed a long time ago. Wondering if having the wrong immobilizer could cause that?  I have to tear it apart this weekend and look at the system. Hopefully I can just re-use the current immobilizer that’s in there right now.

Thank You!

The 2005 - 2006 Cobalt is slightly different from the 2007 - 2010 models.  The XPressKit DB-ALL is the

only listed combo ( door lock / bypass ) module listed.  The XK09 with DLGM5X firmware will onlyhandle the door locks, not the bypass function. 

Having a previously installed R/S system that didn't work well might not help and only confuse matters. 

I have removed a lot of non-working systems and found it is usually better to try and start fresh rather thantrust any existing R/S wiring or components.  Assuming the Cobalt has an automatic transmission and no Factory Alarm system, the R/S w/keyless entry install shouldn't be too bad.  If your factory ignition key has a + symbol in a circle stamped on it, you have the optional PK3+ immobilizer system.

Here is a link to an excellent wiring guide for your Cobalt :  https://www.the12volt.com/installbay/file.asp?ID=717

My "go to" full featured bypass module would be the iDatalink ADS DL flashed with ADS DL GM2 firmware

connected to the R/S ( 4103 ) in the W2W mode.  However, you can use a immobilizer bypass and hardwirethe door locks and trunk release.  For the door locks, I think I would use a Directed 451M door lock modulebecause of the one-wire resistance multiplex system.  The 451M kit includes the 1.5K ohm resistor neededfor Unlock.

Soldering is fun!

Awesome guide! Thanks!

it is an auto transmissoin and it does have a factory alarm (horn beeps and lights flash). The key does not have the + symbol.

Couple questions:

• What does the 451M actually do? I guess more specificly, how is it wiring into the system? (i.e. wired from r/s, through 451M, to each door lock?)
• What is the advantage of using DB-ALL over just using a plain bypass (PLJX).
• Ok, I think after getting a fresh nights sleep its getting a little easier to understand.... let me know if I'm wrong:
• Using just a plain bypass (PLJX) is best if you want to do just remote start and nothing else. You can still add the unlock/lock and trunk pop features of the R/S system but it's more wiring and finding specific wires in the car.
• Using the DB-ALL makes it an easier install because it can be programed to the specific car and there is less wiring involved to make all the features of the R/S work.
• The R/S system is a generic system that can work on all cars, however you need the bypass unit (PLJX, DB-ALL, etc...) to "communicate" between the R/S and the specific car... so in affect, the bypass is kinda like a translater.
• It's better to spend the extra money on the DB-ALL and program it to the car because the install will be easier basically.

Looking at the cobalt wire diagrams, wiring the trunk pop to the remote start looks easy. However, on the remote start unit itself, it has a lock output wire and an unlock output wire. According to the cobalt wire diagrams, there is no one wire that i can "wire into" to unlock or lock all the doors. I guess I was kinda hoping for an "unlock" wire that would unlock all doors and a lock wire that would lock all doors when a signal was sent to it. I would have just hooked the R/S unlock / lock output wires to those wires. If that makes sense...

Sorry for these dumb questions / statements.  I'm really trying to learn all this. I'm not afraid to attemt stuff myself (thats how I learn the best) but I like to get a little background on the parts required before I start clipping wires.

The Factory Alarm complicates things.  Disarming the car prior to a remote start or door unlock or

trunk pop could be an issue.   The DB-ALL will make things easier.  I would recommend making the4103 to DB-ALL connections in the W2W mode ( don't go D2D and use the D2D harness ).  Follow the DB-ALL GM5 Type 2 diagram, making all the necessary connections hardwired ( all blue dashed lines ).  Do this "on the bench", with all solder joints and heat shrink tube for 100% absolute reliability, prior to install.  Ensure the DB-ALL supply source flashes ( loads ) the module with the correct GM5 firmware and includes the corresponding install guide.

If the you went the other route with bypass module only ( PLJX ), the 451M could handle the door locks. 

Here is a link the 451M install guide : https://www.the12volt.com/installbay/file.asp?ID=726  You would followType H diagram with no resistor for the lock output and a 1.5K ohm resistor for the Unlock output.

Here is a link to Ready Remote for more wiring info :

http://www.readyremote.com/main.asp?make=Chevrolet&model=Cobalt

The Cobalt isn't the easiest car to learn on but go slow and continue your research until you feel ready

to start.  Most of the wires are at the BCM in the center console - passenger side.  During the previous system's removal research that and try to get an understanding of what / how the original system worked. It could provide some insights.  ( There are many different ways to install / wire-up a vehicle.)

Soldering is fun!

I want to thank you for all your help!

First since she already has a remote start in the vehicle (same brand), she must have some sort of bypass, so I will tear it apart and look at what she has and go from there to determine what immobilizer I should get. If she already has the DB-ALL, then I’m set, if not, I’m going to buy it… Seems the easiest route to go… 

I plan on doing exactly what you said about previous system removal.  I plan on taking a lot of pictures to incase I need to retrace things or reference the old install after I get it out.

I would be buying the immobilizer off Amazon so I don’t think they will program it for me, however I can also buy the programming module (XKLoader2) for $30 and do the programming myself. Then if I decide to put a remote start in my other car, I already have the programmer…I figure if I take my time, read the install instructions very carefully, reference the old install… I should be good to go...

Again…Thank you!