2006 Saturn Ion, Door Lock/Unlock Wires

I was starting to install an alarm in my 2006 Saturn Ion 2 yesterday, and started by pulling off the door panel to access the power door lock wires to determine if they were positive or negative triggered so I could connect the correct wire from the alarm. I quickly discovered that Saturn Ions use a negative trigger system. The white wire shows voltage, then when the button is pressed the voltage goes away. The other wire is black. It's the ground wire, or just a wire to make a complete circuit kind of like a light switch in a home. Well, to test and verify that I needed to connect my alarm's negative door trigger wire to the switch wire, I grounded the white wire. When I tapped the ground to the spot where I shaved off a bit of insulation on the wire, the door would lock. But no matter how many times I did this, it would NOT unlock! So I went online and discovered that Saturn power door lock switches get their signals from the BCM (computer). When you press the button to lock, a solid ground is sent to the switch. When you press the button to unlock, a ground with 1.5K ohms of resistance is sent to the switch to unlock the doors.

SSSOOO... I gave up and put the alarm wiring harness back in the box and quit for the day!

My reason for this post is that I'm trying to figure out HOW you can run a door trigger wire from an alarm module to a switch like the one in my 2006 Saturn Ion 2? My alarm won't sense any resistance, only voltage or ground. So how do I get the alarm to UNLOCK my door(s)? I'm guessing a relay wouldn't help at all.

Anyone else run into this same issue with a Saturn? If so, how did you remedy the situation and get it to work like it should? Or did you?

I'm going to keep trying to find an answer. If I do, I'll post it here as a comment.

Thanks!

You have it pretty much figured out. You didn't mention which Brand and Model of aftermarket alarm system you are installing but if it outputs the common (-) 200 mA lock signals you will need some relays or a Directed 451M door lock module. The 451M is about $11 and is a nice compact package that comes with an assortment resistors that will include the 1.5K ohm resistor you need. Also, rather than going into the doors and all the headaches that come with that, the Lock wire is found inside the vehicle at the BCM. Here is the lock wire info from Bulldog Security :

POWER LOCK     WHITE (1-Wire System) See NOTE #2     @ BCM C3, PIN 33
POWER UNLOCK     Same wire @ BCM C3, PIN 33

NOTE #2
LOCK IS A STRAIGHT (-) NEGATIVE TRIGGER.
UNLOCK IS A NEGATIVE THRU 1.5K OHM RESISTOR

If you had two SPDT 30/40 Amp relays and a 1.5K resistor plus an inline fuse holder with a 10 Amp fuse, you could wire it up following this diagram :



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Soldering is fun!

It's a Scytek Astra A20 alarm. I've had nothing but excellent luck with this brand, and it's the only alarm brand I've purchased in over 10 years! What I love about Scytek is the endless list of features you can turn on or off or program different ways, plus the fact that they are all made in USA! I used to be a stickler for nothing but Code Alarm brand when they were made in USA, but no so much anymore. Scytek is ALL I'll buy.

So anyway, I appreciate your helpful response!

I just took another look at the wiring diagram in the owners manual for the alarm and it looks like this could be actually pretty simple to remedy! Since it has separate outputs for lock and unlock, I'm thinking all I have to do is put a 1.5k resistor at the end of the unlock wire from the alarm at the white wire! I can actually run BOTH the wires, lock AND unlock, to that white wire from the switch and just put the resistor on the unlock wire. Since it would only get a signal from one of those two wires at a time, it wouldn't be dangerous or stupid. LOL!

I think this is actually easier now than I figured it would be! I just panicked when I was starting to put the alarm in when I decided to start with the lock/unlock wire!

As for your suggestion that it could be easier to wire the lock/unlock at the BCM instead of the switch, I think it probably would actually be easier to go to the switch wire because where it goes through the door jamb, that harness pulls out and it's easy access to the lock/unlock wire. It's a lot closer to get to than running another wire through the firewall. I already have other wires to run to the engine compartment, from both the alarm AND the new stereo going in, so the fewer wires I have to run through the firewall the better.

I'm STILL going to look into one of those DEI modules you mentioned. I can probably find one cheap on eBay!

Thanks again! Your reply was VERY helpful! At 62 years old and after installing alarms and stereos for over 45 years you would think I could figure more of this stuff out on my own, but every once in a while I get stumped.

I'll let you and everyone know how it goes from here out! Now I just have to find a resistor! Not like you can walk into your local Radio Shack and buy one! LOL!



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Good info on the Scytek brand. I've never used one but going by their install guide, the lock outputs are not from internal relays. The current G20 model has (-) lock outputs rated at 500 mA. That current rating might be enough to support a direct connection to the White one-wire vehicle lock wire. Some car brands and models need a stronger ground signal, hence the 451M or relays. Too bad about Radio Shack. Makes finding a resistor a bit harder. EBay has them, you could even get an assortment pack. You should be OK with 1/8 or 1/4 watt resistors. As mentioned, the resistor is included with the 451M module.

As for the actual White wire, the BCM is inside the car, part of the fuse box. Makes finding the correct wire easier when yop have the Plug and Pin number. Going into door, with trim removal and the flex harness in the doorjamb can be an issue. Here is the info from Bulldog Security.

THE BCM (Body Control Module) IS PART OF THE FUSE/RELAY BOX IN THE LOWER CENTER OF THE DASH, JUST BELOW THE HVAC CONTROL ASSEMBLY.IT HAS THE FOLLOWING CONNECTORS : C1-37 PIN BLACK PLUG, C2-38 PIN GRAY PLUG, C3-56 PIN BLACK PLUG, C4-56 PIN GRAY PLUG, AND C5-6 PIN GRAY PLUG.

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Soldering is fun!

After looking at relays on eBay and searching for a 1.5K resistance, I'm only finding them rated in watts or percentages, which makes it pretty confusing on how to chose one. Yes, they are VERY cheap! They have 10-25 packs for less than a couple bucks! But I can't figure out the correct one to buy. So I'm glad you mentioned 1/8 or 1/4 watt. I know nothing about resistors other than how they work. Maybe I'll order some of both 1/8 and 1/4 watt, then measure their resistance once I get them.

I forgot to check into that DEI module, so I'll do that now!

Thanks again!

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Still haven't ordered the resistors yet because I'm still not sure on what wattage rating to buy. Does it even matter? I find a bunch of 1.5k ohm resistors but in different wattage ratings. Also finding different tolerance levels. Does tolerance matter? Thanks. Oh, and I just now ordered that DEI door lock module you suggested!

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I usually get the higher wattage rating since the conductors are slightly larger and less likely to physically break.

I typically select resistors with a 5% tolerance or better. Say you had a resistor rated at 1.5K ohms and it had a 20% tolerance rating. The actual resistance could be anywhere from 20% above or below that value. 5-10% should work fine.

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My ex once told me I have a perfect face for radio.

I would suggest as Kreg says to use the 451M and don't run the outputs directly to the white wire to be on the safe side. If you burn out those outputs your going to have to replace the whole brain module to get the lock outputs working again. The 451M would keep those outputs from ever being overdriven with current and the proper resistor is included in the kit. If you do run them direct I would think that diode isolation would be necessary.

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Steve G

Got the 451M ordered and should get it today! Also got a few extra resistors as suggested (ordered before the module). Now the only thing is to find time, and a dry day! Had the alarm since the beginning of the year, and like they say, it's not going to install itself! LOL! I gotta get on this! Too much car audio installed to not have a good alarm with proximity sensor! The factory alarm has done okay so far but I need to upgrade! Just had to get this unlock issue worked out so I don't have to carry around two remotes.

As for connecting the lock/unlock wires from the alarm to the BCM, that seems like a huge pain! It's too hard to identify the correct wires coming out of the BCM, and even harder to get to them. But I'll check it out.

Updates to follow!

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geepherder wrote:

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I usually get the higher wattage rating since the conductors are slightly larger and less likely to physically break.

I typically select resistors with a 5% tolerance or better. Say you had a resistor rated at 1.5K ohms and it had a 20% tolerance rating. The actual resistance could be anywhere from 20% above or below that value. 5-10% should work fine.

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I got the 1.5k ohm 1/4 watt with 5% tolerance from eBay. That was before I ordered the 451M but at least I'll have some on hand if needed later. At $2 for 5 I can't lose much if I don't use them.

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