98 bcm in a 99 car will it work?
TECH Fanatic
Joined: Nov 2011
Posts: 1,367
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From: Woodstock, GA
Rockauto shows the same part number for each year. I replaced mine a while back when I was having issues with my keyless remote not working. The VATs resistance on the key will have to match it or you'll get a security warning and it will not crank.
Joined: Nov 2003
Posts: 11,325
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From: Jacksonville, FL (originally from Toronto Canada)
TA Freak is correct - all 98-02 F-bodies now use the same BCM replacement part. That was not true of the originally installed BCM. GM used to produce two different parts - one with the optional alarm system and one without. New ones now all have the alarm capability but a used one might not so you might lose your factory alarm system if you have one.
Also as TA Freak mentioned, another problem with a used BCM is matching the VATS value. Unless you get the original key from the donor vehicle, you will have to determine which of the 14 possible resistance values it is programmed to recognize. A new BCM would automatically program itself to match the first key used but they can never be reprogrammed after that first time. So you'll have to get a bunch of different resistors to make all 14 possible values and try each one until you can get the car to start. Then you can either do a VATS bypass with that resistance value or get a new ignition key cut to match your current key but with a resistor pellet that matches the used BCM. If you can get the original key from the donor vehicle, you can just measure the pellet resistance and get yourself a new key to match.
Also as TA Freak mentioned, another problem with a used BCM is matching the VATS value. Unless you get the original key from the donor vehicle, you will have to determine which of the 14 possible resistance values it is programmed to recognize. A new BCM would automatically program itself to match the first key used but they can never be reprogrammed after that first time. So you'll have to get a bunch of different resistors to make all 14 possible values and try each one until you can get the car to start. Then you can either do a VATS bypass with that resistance value or get a new ignition key cut to match your current key but with a resistor pellet that matches the used BCM. If you can get the original key from the donor vehicle, you can just measure the pellet resistance and get yourself a new key to match.
TECH Fanatic
Joined: Nov 2011
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From: Woodstock, GA
WhiteBird00,
One thing that I did was install a potentiometer that had the resistance range of the resistances used and could dial in each one until I found what matched the BCM and no security warning, then I found the correct values of resistors to get that value from the pot and solder that in. Didn't want to leave the pot in there ... if you know what I mean. LOL. Could leave me stranded .... It was easier than swapping out resistors until I found what worked.
One thing that I did was install a potentiometer that had the resistance range of the resistances used and could dial in each one until I found what matched the BCM and no security warning, then I found the correct values of resistors to get that value from the pot and solder that in. Didn't want to leave the pot in there ... if you know what I mean. LOL. Could leave me stranded .... It was easier than swapping out resistors until I found what worked.
Joined: Nov 2003
Posts: 11,325
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From: Jacksonville, FL (originally from Toronto Canada)
That's a great idea! There are VATS kits that include a box with a rotary switch connected to each of the possible resistor value combinations - they are very simple to use but are ridiculously expensive. A potentiometer does the same thing without costing anywhere near as much. Did you have any trouble finding a pot with the right range? Radio Shack maybe?
TECH Fanatic
Joined: Nov 2011
Posts: 1,367
Likes: 144
From: Woodstock, GA
That's a great idea! There are VATS kits that include a box with a rotary switch connected to each of the possible resistor value combinations - they are very simple to use but are ridiculously expensive. A potentiometer does the same thing without costing anywhere near as much. Did you have any trouble finding a pot with the right range? Radio Shack maybe?
... I'm sure that one could be had online. Radio Shack is fairly expensive. Makes me think of making a rotary switch like you mentioned.
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Joined: Nov 2003
Posts: 11,325
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From: Jacksonville, FL (originally from Toronto Canada)
You can't delete VATS - it's in the BCM. You can program the PCM to ignore the fuel enable signal sent by the BCM as part of VATS but the BCM itself is not programmable so you can't get rid of the rest of the system (specifically the starter relay disable).
Another possibility is to use a programmer to make the PCM ignore the missing fuel enable signal AND rewire the starter relay so that it doesn't rely on the BCM to activate. You will always have the SECURITY light on in the instrument cluster but I suppose you could eliminate that by taking apart the cluster and desoldering the LED.
Using a potentiometer to determine the correct resistance value to bypass VATS would be simpler if you have any electrical experience.
Or you could buy a new BCM for $193, simply plug it in and start the car with your existing key.
Another possibility is to use a programmer to make the PCM ignore the missing fuel enable signal AND rewire the starter relay so that it doesn't rely on the BCM to activate. You will always have the SECURITY light on in the instrument cluster but I suppose you could eliminate that by taking apart the cluster and desoldering the LED.
Using a potentiometer to determine the correct resistance value to bypass VATS would be simpler if you have any electrical experience.
Or you could buy a new BCM for $193, simply plug it in and start the car with your existing key.
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been using the potentiometer method to find unknown resistor values of a BCM for awhile. I use a pot with a wide range of resistor value to cover all the 15 different values. just unhook the wires from the key switch and "plug in the pot" and dial in the the first resistor value and see if it starts. if not I let the BCM reset (light off) and go to the next value until it starts. I hook a digital meter to set my value on the pot.
Joined: Nov 2003
Posts: 11,325
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From: Jacksonville, FL (originally from Toronto Canada)
While there were 15 resistor values specified by GM for VATS, only 14 of them were ever used in f-bodies. You can ignore the #1 value in most tables (392 ohms) because it was never used in our cars.
The values that were used are:
2 - 523
3 - 681
4 - 887
5 - 1130
6 - 1470
7 - 1870
8 - 2370
9 - 3010
10 - 3740
11 - 4750
12 - 6040
13 - 7500
14 - 9530
15 - 11800
The values that were used are:
2 - 523
3 - 681
4 - 887
5 - 1130
6 - 1470
7 - 1870
8 - 2370
9 - 3010
10 - 3740
11 - 4750
12 - 6040
13 - 7500
14 - 9530
15 - 11800
