I'm pretty sure I had tried wiring everything back up to stock and it didn't work. That's what you meant by disconnect the alarm, right? I probably won't get a chance to try that again just for good measure until next week. Thanks for all your help so far, you've been extremely generous.

If it doesn't work with the stock wiring in place, is there a way to test the BCM, or a way to test it regardless to see if it is functioning rather then looking for a wiring fault?

When it comes to swapping the BCM if neccesary, does the dealer have to do it or can I? I'm thinking there would be a complication with matching the BCM's VATS to the chip in the key.

 

I don't know of any way to test the BCM other than using deduction to eliminate all other possibilities. Fortunately, replacing the BCM is quite easy and programming it for VATS is even easier. New BCMs come unprogrammed so they will match the first key used. All you do is turn the ignition on and off eight times in a row to program the BCM to match your key.

 

Tyring a used BCM would be a craps-shoot whether or not it would work, right?

 

You can make a used one work but you have to either get a new key with the correct resistance (one of 15 values that you can only determine by experimenting) or bypass the VATS system with the kit that installers use for remote starters.

 

I found something I posted on the12volt.com that said I did in fact wire it back to stock and it did not work. So, maybe it's time to try a new BCM. i just hate to spend $150-200 to get something that may not work. Someone on that post mentioned that there would be locking problems if the factory alarm wasn't shut off. As I mentioned earlier there have been times that it has gone off, no sirens, but lights flashing. Typically when the door is open and i probe the wires with the test light, then it goes off a few seconds later.

I found used BCM's and VATS bypass kits on ebay. Good idea, or bad?
I thought i could buy a used one(but i think their are options that have to match like keyless entry etc.., right?) see if installing it fixes that, then worry about getting a VATS bypass kit to get her to start.

 

I hope that the place that installed it refunded the labor.

PS; I would take it back to them and tell them that you think they fried your bcm, and most chain stores will have it checked out and since they are hte ones who worked on it, theyll have to incurr damages. But, by some chance if its something that they had nothing to do with (they more than likely did in your case), then you would have to pay for the diagnostics.

 

You should always program the factory alarm off when installing an aftermarket alarm. This is a simple procedure listed in your owner's manual (it's also posted on this board someplace).

There are only two BCM models available for 98-02 f-bodies - one with the alarm system and one without - so it should be fairly easy to find a matching used one. Also, you can avoid buying a VATS bypass kit by measuring the resistance in your key and then buying the appropriate resistor to "jumper" the two VATS wires at the column. The kits are more convenient but also more expensive.

 

I just bought a used BCM off ebay for $20 bucks shipped. I'll slap it in as soon as it comes in and post the results. I have a buddy that thinks he knows how to measure the resistance of the key. I may need some guidance on measuring it and picking the correct resistor though, and then which wires to tap into.

 

There's no point measuring the resistance in your existing key because you only have a 1 in 15 chance that it will match the used BCM. You will have to get a resistor for each of the possible values and just try each one until you find the one that lets the car start with the replacement BCM.

Here are the possible values for the key resistors:

• 402 ohms (acceptable range 386-438)
• 523 ohms (acceptable range 502-564)
• 681 ohms (acceptable range 650-728)
• 887 ohms (acceptable range 850-942)
• 1130 ohms (acceptable range 1085-1195)
• 1470 ohms (acceptable range 1411-1549)
• 1870 ohms (acceptable range 1795-1965)
• 2370 ohms (acceptable range 2275-2485)
• 3010 ohms (acceptable range 2890-3150)
• 3740 ohms (acceptable range 3590-3910)
• 4750 ohms (acceptable range 4560-4960)
• 6040 ohms (acceptable range 5798-6302)
• 7500 ohms (acceptable range 7200-7820)
• 9530 ohms (acceptable range 9149-9931)
• 11800 ohms (acceptable range 11328-12292)

 

It's the BCM!!! I got the used one in the mail, and they worked like magic! Of course I wasn't lucky enough to get the right one to start the car.

I hate to ask another favor, but could you explain which size of resistors I need to pick up to wire into place. Someone told me there are two white wires, and made it sound like I wire the same size resistor inline on each of them. I just have to figure out which size. Does this sound right? THanks again so much for all your help!!!

 

Because you don't know which is the correct resistance to match the used BCM you bought, you'll have to buy one to match each of the fifteen possible values listed above (actually, fourteen because you already know the value in your key doesn't work). So, once you have your fourteen resistors in hand, you try each one as a jumper across the two wires (input and output) for the VATS system until you find the one that works. The idea is that you're disconnecting the connection that goes through the ignition cylinder and key and replacing it with a permanently mounted resistor in the circuit so that the BCM thinks the correct key is always there.

You can get the two wires you need at the base of the steering column or at the BCM itself. Most people go with the steering column because you can unplug the connector there so you don't need to cut the wires. Remove the knee panel under the steering column and look for a 2-pin black connector containing a white with black wire and a purple with white wire. Unplug the connector and use your resistor to connect the two wires together (on the side of the connector that goes into the dash - not the side that goes to the ignition switch). Once you find the correct resistor it's best to solder it in place and insulate with electrical tape.

The VATS bypass kits are much more convenient because they just plug in but they're also much more expensive. You should be able to get all fourteen resistors for just a few dollars.

BTW, you may need to get more than one resistor to make any given value in the list because some of the listed values are unusual. Your best bet would be to take the list to Radio Shack or other electronics store and have their people put together a collection of resistors that will yield each value. For example, resistors in series yield the sum of the resistances whereas resistors in parallel yield the average of the resistances.

 

Picked up a bunch of resistors that I think will net the appropriate values, and will give this a wirl tonight. I just want to make sure I'm doing it correctly. Do I unplug the connector and simply run the resistor from one pin to the other and leave it that way, or do I need to strip the wires and connect the two and plug it back in? I assume it is the latter of the two. I'll let you know how it works out!

 

No, it's the former. You want the resistor to replace the connection through the ignition cylinder so you need to unplug the connector and then connect the two wires together with the resistor (don't plug the connector back in).

 

Well, I must have done something wrong. Here's an example of what I did. for the 402 ohms I connected a 100 ohm and a 330 ohm by twisting one end to the other end, then sticking one free end into one of the female slots in the plug and the other free end into the other female slot of the plug. By "the plug" I mean the female plug with the two white wires that head into the car. More examples are, 4750 ohms I used a 4.7k resistor; 7500 ohms I used 4.7k/1.5k/1.5k I'll try a couple more, perhaps the 5% variance pushed me over on a couple of these. Maybe I just need to get a bypass kit and call it a day.

Thanks again for all your help, you're way too nice. I wish there was something I could do in return for all your time. I know you have to be pretty frustrated with me by now

 

You may have the wrong connector. There shouldn't be two white wires - there should be one white with black stripe wire and one purple with white stripe wire.

In some cases the resistor tolerance may also contribute to the problem. For example, your 4.7K resistor is well within the tolerance of the 4750 but the 100 and 330 puts you very close to the range limit of the 402 (386-438). By the time you add a 5% variance you could be as high as 451 ohms which is outside the range.

I did a little research on bypass kits and found they're not as expensive as I had thought. The self-learning ones are still in the $60 range but a manual one is available for $20 at J.C Whitney. There is also the DEI kit (a very trusted manufacturer) for only $8. However, it is intended to work only during use of a remote starter and still provides normal VATS key function otherwise. You might have to play with the connections to get it to work all the time.

 

I found a connector that had white/purple, and white/black on the male end. The female end was wrapped in orange and I thought the wires were both just plain white, but couldn't see really well. I was plugging the resistors into the female side, which was the wrong side from the way it sounds.

I did notice how close I was to some of the limits and tried values closer to the middle, but they didn't work either.

I'll probably just pick up a VATS bypass sometime today and call it a day.

 

I cut the white/purple and white/black wires from the harness describe above and wired up the values of resistors as described above, but nothing worked for me. I did notice that after cutting the harness the "security" light was on. It did go off at one point when I had some resistors hooked up, i tried starting, but nothing happened and the light came back on.

I did realize that all my resistors were 1/2 watt, but the 100 ohms were 1/4 watt. Could this have been a problem?

I guess I'll get the $20 vats bypass from jcwhitney (valiant brand product, right?), but looked like a lot of wiring. There's on on ebay that is only three wires, looks pretty easy. http://cgi.ebay.com/ebaymotors/GM-VA...mZ220024542780

 

That's an interesting device they're selling on eBay. It appears to work on an entirely different principle than all the others - instead of fooling the BCM into thinking the proper key is inserted it tells the PCM to go ahead and start regardless of what the BCM thinks. I have two concerns with this method. First, there are two circuits that have to be enabled by the BCM - the fuel injectors and the starter relay. Their box seems to handle only the fuel injectors. You may have to hardwire the ground of the starter relay instead of letting the BCM provide the ground. Second, the BCM will continue to illuminate the security light on the dash.

I would ask the vendor about those things before buying one.

 

So, I was wiring things up properly? Correct wires and method? Does it matter that the 100 ohms were only 1/4 watt?

The vendor did say that I would possibly have to jumper a wire from the fuel injector wire to the starter wire, and they suggested I cut the wire that illuminates teh security light on the dash(That light would drive me nuts for sure)

 

Well, I'm still not sure you've got the right wires. You keep mentioning white/black and white/purple but the wires are actually white/black and purple/white (it may just be semantics but I always list the base color first, followed by the stripe color). The 1/4 watt resistor should work fine - it's a very low current circuit.

Did the vendor also mention that you would have to disable the factory alarm system (if you have it)? If the starter disable is bypassed the BCM will trigger the alarm if you attempt to start the car with the incorrect resistance in the key. All said, I think I would stick to the tried and true VATS bypass that fools the BCM into thinking the correct key is inserted. The other type is an interesting idea but it seems to have a number of drawbacks.