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Discussion Starter #1
My truck has a lot of miles on it, and it's had a few gremlins that have plagued the electrical system since day one of me owning it. First thing I noticed when I opened the door after buying it was that the door chime was buzzing even without the key in. That was annoying, so I eventually opened the body control module up and popped off the little chime buzzer. Things were fine for a while, other than the security light always flashing when the door is open. Then a while back, the radio stopped turning off on its own. I would park, come back later and find it still playing. Things were getting annoying. The alarm would also go off occasionally. I had no idea the truck even had and alarm until it started beeping in the gas station parking lot. About this time, the truck developed a parasitic battery drain. For months I've been pulling fuses and examining wires, and at this point I'm almost certain it's the BCM faulting. I've already done basic stuff like changing the door plunger.

Since changing the BCM involves reprogramming the system, I got a Tech2 knockoff in hopes of DIYing it. I used that scanner to dig into the codes my more basic scanner hadn't shown me. One of these was a U1301. "High Voltage On Class 2 Serial Data Circuit " Could this also be related to the failing BCM? It was present in the BCM subsection on my scanner, but this thing is a bargain basement Chinese tool, so I'm not putting a lot of faith in it.

My main questions are for anyone who has done a BCM swap. If my cheap China scanner can't get the job done, or the part I buy is a dud, can I just put the old BCM back in without reprogramming it? I'm wary of this truck getting immobilized. Has anyone had any luck doing the Passlock II bypass, and if so will this allow me to use regular, non-resistor embedded ignition keys? I'm assuming if my scanner fails, I'll have to open the steering column up and do that wire splice that bypasses Passlock. I don't think anyone is interested in stealing this truck with over 270k miles on it.

My last question is about how failure prone these BCMs are. Is this something I can pull from a junkyard truck, and if so which models have the same BCM? I assume the Blazer, Jimmy, Astro, Safari, Suburban, Yukon and Silverado all have that same module, but correct me if I'm wrong. I also assume it won't matter if I find a good BCM in a 4cyl S10 when mine is 6cyl.
 

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Mr Goodwrench's Evil Twin
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Sounds like your ignition is worn out... all your symptoms are consistent with a worn ignition. It thinks the key is in the ignition when it's not. Not uncommon in higher mileage GMs. I'd replace the ignition lock cylinder and by the sound of the issues you're having, the ignition switch also. I'd do these before even thinking about replacing the BCM
 
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Discussion Starter #3
Sounds like your ignition is worn out... all your symptoms are consistent with a worn ignition. It thinks the key is in the ignition when it's not. Not uncommon in higher mileage GMs. I'd replace the ignition lock cylinder and by the sound of the issues you're having, the ignition switch also. I'd do these before even thinking about replacing the BCM
Do you think that would also explain a new fault I found today, where the drain goes absolutely nuclear with the key on/ ignition off? The battery will drain down in 15 minutes if you leave the key on. That's why I'm finally fixing this. I had just thrown on a cutoff switch for the battery to stop it running down overnight. But I don't want to sit somewhere with key on for a few minutes and not have enough juice to crank.

I think you might be on to something with the ignition. I've ordered those parts, so we'll see how it goes. I assume I'll still either be relearning or bypassing the Passlock. It looks like the part I ordered comes with resistor keys. If not I'll just splice the wire.
 

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You don't have a chip embedded in the keys. The chip is in the ignition switch's key cylinder. GM idea is that if someone uses a slide hammer to pop out the lock it won't start because they also popped out the chip.
My 05 GXP has the Passlock 3 and the key is bigger because the chip is in it. Quite different key than any S10 uses.
When you replace the switch your Tech 2 will do a security relearn quickly. Those clones aren't really clones. When Bosch bought out Vetronics they moved the manufacturing to China. Can you say, "Multinational Corporate Rippoff? Bosch didn't lower the price back when they were $3K. After the MIDI came out Bosch stopped buying the Tech 2 from the Chinese. So they just kept making them with a few minor adjustments to make them for even less. Like a screen that's not quite as bright. But basically they're still the same gadget from the same actual factories.
If you do need to reprogram the BCM you'll need to buy a license from ACDelco TDS to get the programming software.
It's like $40 for 1 vehicle, good for 2 yrs.
 
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Mr Goodwrench's Evil Twin
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Do you think that would also explain a new fault I found today, where the drain goes absolutely nuclear with the key on/ ignition off? The battery will drain down in 15 minutes if you leave the key on.
The issue with the ignition has likely taken its toll on your battery. Parasitic draws (the technical term for an issue such as yours) aren't good for a battery. Get it tested at your favorite local auto parts store.
 

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Discussion Starter #6
You don't have a chip embedded in the keys. The chip is in the ignition switch's key cylinder. GM idea is that if someone uses a slide hammer to pop out the lock it won't start because they also popped out the chip.
My 05 GXP has the Passlock 3 and the key is bigger because the chip is in it. Quite different key than any S10 uses.
When you replace the switch your Tech 2 will do a security relearn quickly. Those clones aren't really clones. When Bosch bought out Vetronics they moved the manufacturing to China. Can you say, "Multinational Corporate Rippoff? Bosch didn't lower the price back when they were $3K. After the MIDI came out Bosch stopped buying the Tech 2 from the Chinese. So they just kept making them with a few minor adjustments to make them for even less. Like a screen that's not quite as bright. But basically they're still the same gadget from the same actual factories.
If you do need to reprogram the BCM you'll need to buy a license from ACDelco TDS to get the programming software.
It's like $40 for 1 vehicle, good for 2 yrs.
Mine is called the Vident iLink400. Priced at $158.

The issue with the ignition has likely taken its toll on your battery. Parasitic draws (the technical term for an issue such as yours) aren't good for a battery. Get it tested at your favorite local auto parts store.
Oh yeah, I bet it's pretty bad. This is a cheapo Walmart battery, too. But what I've noticed is that the drain is very slight if I don't have the ignition in the key on position. Can take days to drain down. This truck had a bad motor and sat up all summer, and the battery went a whole month without charging all the way down. At like week two, the interior lights were visibly dim. I threw a charger on it before sending it off for its engine swap, and it was at like 65%. Since I got it running again, I've been trying to sort out the rest of its issues, and as such had to take the dashboard apart. You have to move the shift lever down to get the bezel off, and so while I was messing with the dash, I had the key on. The battery went from a full charge to nothing in the span of that time. The radio wouldn't even turn on. I think I may redo my tests with the key on, because I can at least see if one of the key on systems is pulling massive volts.
 

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Mr Goodwrench's Evil Twin
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Mine is called the Vident iLink400. Priced at $158.



Oh yeah, I bet it's pretty bad. This is a cheapo Walmart battery, too. But what I've noticed is that the drain is very slight if I don't have the ignition in the key on position. Can take days to drain down. This truck had a bad motor and sat up all summer, and the battery went a whole month without charging all the way down. At like week two, the interior lights were visibly dim. I threw a charger on it before sending it off for its engine swap, and it was at like 65%. Since I got it running again, I've been trying to sort out the rest of its issues, and as such had to take the dashboard apart. You have to move the shift lever down to get the bezel off, and so while I was messing with the dash, I had the key on. The battery went from a full charge to nothing in the span of that time. The radio wouldn't even turn on. I think I may redo my tests with the key on, because I can at least see if one of the key on systems is pulling massive volts.
Batteries can act ok then take a nose dive pretty quickly. Sounds like yours has very little reserve capacity. Reserve capacity is essentially a measurement of reserve power a battery has under a specified load. If your alternator dies while driving, the better the reserve capacity, the farther you can drive on just the battery. Walmart batteries are far from quality built. They have shorter lifespans than any other batteries, in my experience. Often times less than a year. I would get that ignition taken care of and then get that battery tested before you go testing anything else. It's likely just a junk battery.
 

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Discussion Starter #9
I am now about half way through changing the ignition and lock. While I was waiting for the parts I've been driving the truck, and the strange electrical issues have continued. Today on the highway, all the dash lights suddenly came on and the tach spiked to the top end. No actual change in the truck's performance. The lights, including the airbag light and and check engine light stayed on for a second before turning off. The stereo also started skipping. Then everything went back to normal. The event lasted about 15 seconds.

I was hoping I could get away with not redoing the ignition wires, but after today's problem I won't be taking any chances.
 

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Mr Goodwrench's Evil Twin
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If the new ignition switch and lock cylinder doesn't take care of it, take a good close look at your battery cables. You may have some corroded cables. Even if they look ok on the ends, corrosion can get as far as a couple of inches underneath the insulation on the cable. So its best to check the cables for resistance or better yet, voltage drop.
 
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If the new ignition switch and lock cylinder doesn't take care of it, take a good close look at your battery cables. You may have some corroded cables. Even if they look ok on the ends, corrosion can get as far as a couple of inches underneath the insulation on the cable. So its best to check the cables for resistance or better yet, voltage drop.
Like I said I only got about half done last night before sundown, and didn't put the cylinder in yet. Got the wiring done though, and left it overnight to see if it would charge down rapidly. It didn't drop to 70% or so like was doing before. Only dropped from 100% to 94%. I've tested the switch and it cranks the truck, no security problems so far. I'll be installing the cylinder in a couple hours. This truck has some questionable wiring done for a trailer brake controller from its previous life, so I removed all that from the dash. Some of its wires ran back to the battery, though they weren't hooked up. I'll start my tracing from there and remove all parts of the old controller wires going into the dash.
 

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Changing those parts did nothing. I still get a bad drain. After another entire day of testing wires and pulling fuses, I've gone ahead and ordered a used BCM. If it doesn't work I'll just be out the $11 for it.
 

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Mr Goodwrench's Evil Twin
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Have you checked your door switches? And have you had that battery tested? From what you previously mentioned I strongly suspect your battery may be good as a paperweight but not much else. BCMs don't often fail. I can only recall ever seeing one s10, well, it was a blazer, that actually had a BCM fail and it was a salvaged flood car.
 

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Just to add to the list of things my truck is supposed to do that it no longer does, the daytime running lights don't work. I noticed this happening last week, but it went away briefly. It's back today.

Have you checked your door switches? And have you had that battery tested? From what you previously mentioned I strongly suspect your battery may be good as a paperweight but not much else. BCMs don't often fail. I can only recall ever seeing one s10, well, it was a blazer, that actually had a BCM fail and it was a salvaged flood car.
Yes, I've changed the door switches three times or so now. They activate the lights when they're supposed to, but the radio turn off feature still won't work. The battery was swapped with a known good one from one of my other vehicles and still did the same thing. I've noticed it charges all the way up when I check it after driving.

My truck has had a hard life. It has a checkered past, and in fact the "friend' I bought it from had gotten it as junk. I didn't find out until I searched my VIN and found the auction records. Damage listed as "left rear mechanical" (transmission was grenaded) and nothing about flooding, but who even knows. Looked like it had been used on a farm. I wouldn't rule out anything, as this truck was in an extreme state of neglect when I got it. Rust free but absolutely covered in dirt, inside and out.

I received the "new' BCM today. Of course it's not actually new, because I found out the three key turn trick for programming it won't work on a brand new unit. I'm still unsure of whether my scanner can do the job. I want to try and get it installed on Saturday, since I'm driving the truck long distance on Sunday. However I'm concerned about accidentally immobilizing myself if the new unit is bad. Will the old BCM still work if I swap it back in, or does the truck's computer change after I relearn the new module?
 

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Discussion Starter #15
Today I finally got the BCM swapped. The relearn procedure didn't seem to work, but when I started messing around in the system with my scanner, I was able to get the truck started. So far it doesn't seem to have fixed the issue with the radio, but my daytime running lights started working again. The key buzzer acts like it's supposed to, and the security light is off. However, now my airbag light is on. Gives the code B1001 option configuration error. I can clear the code with my scanner to make the light go away, but it comes back on when I restart. I'll be exploring the menus on my scanner to see if there's any way to keep it permanently cleared.

The big question is whether or not the battery still drains. I used the scanner to power down the BCM, which is a function of it that I previously didn't know I could do. We'll see if the battery is run down in the morning. It's a brand new battery purchased last week, so it shouldn't have any problems like the old one had.
 

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Mr Goodwrench's Evil Twin
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B1001 means that the vin number in the SDM (air bag computer) and the VIN number in the BCM don't match OR the SDM number stored in the BCM is different than the SDM number physically in the vehicle. This is either result of a BCM that has not been programmed or the BCM was previously in a different vehicle. Programming of the BCM is done through a Tech 2. Programming the BCM is the only way to get rid of that code and the air bag light.
 

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Discussion Starter #17
I'm just going to put some tape over the light and pull the fuse for now. After watching the crash test videos of this model, I can safely say I never want that airbag to deploy and roll my head into the door frame. I'll take my chances eating the dashboard if it comes down to it.
 
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