Changing Battery fried the ECM and BCM?

[CaptainKD]

My father has a 2008 Chevy Silverado LT1 4.8 V8 1500 Series. Recently he changed the battery and when he hooked the new battery up the truck would not start or crank. He ended up having it towed to the mechanic and they eventually found the problem was that the truck needed a new ECM and reprogrammed the BCM. The mechanic said more than likely my father did not unhook and hook up the battery in the correct order and it fried the ECM and BCM. He was instructed to disconnect the battery in this order: (-) than (+). And reconnecting it in this order: (+) than (-), this will prevent the ECM and BCM from being damaged.

Can connecting the battery in the incorrect order really cause damage to ECM and BCM?

 

[Ghoster]

With GM engineering... I guess anything is possible, in theory. However I would be very skeptical. I doubt the order of connection could do that. Touching one with the other while they are connected to the battery could cause a probelm, but I would think a bunch of bad things would happen in the fuse box. Maybe if you connected them completely opposite... I would still think you would see other problems. Sounds fishy to me, but hey, it is GM.

 

[Mark20]

I'd have to pop the hood but I think they keep the battery cables lengths just long enough to reach their respective terminals. However some batteries are made with their positive and negative posts reversed. IIRC the negative on our batteries is closer to the engine itself.

Sent from my Xoom using Tapatalk

 

[djthumper]

It could be highly possible with all of the sensitive electronics that are run in the vehicles now days. That has been a general rule that I have followed for years while working on vehicles though. It is also the recommended way to connect jumper cables to keep the arcing down.

 

[Wyle]

Someone might have a more positive answer than me, but I'm pretty sure the only damage you might do is by hooking up the battery cables to the wrong terminals. Assuming you only have one battery in the vehicle, once either cable is disconnected, you can't have any current flow. Touching one disconnected cable to the other battery post/cable also does nothing (except discharge any capacitors??) because there is no means for current flow between battery posts.

The real reason to disconnect the battery when doing repairs (other than reset the PCM after cleaning the throttle body ), is so that the wrench you're using doesn't become the path from some positive lead back through the frame to the battery. Generally, the reason you take the negative off first and connect it last is so you don't have a 5/16" socket on the positive terminal of the battery and hit the ratchet handle to the grounded frame. Since the frame is connected to the negative terminal on the battery it doesn't happen on that side and once its disconnected, you can't short the positive terminal because the frame isn't connected to the battery anymore.

I HIGHLY doubt you can damage any of the computer modules by connecting/disconnecting the cables to the proper battery terminals. I'd be challenging the mechanic(s) to provide a sound explanation of how that happens.

 

[Wyle]

It is also the recommended way to connect jumper cables to keep the arcing down.

Yes and no. It doesn't limit arcing. You should be using the negative cable to relocate the arcing.

Batteries use sulfuric acid, typically 35% strength. Under certain conditions sulfuric acid will give off oxygen and hydrogen gas. In ye ol' days before sealed battery caps, you wanted to connect the negative cable last and to somewhere on the frame away from the battery. Still a very good idea today. Sparks and hydrogen gas don't mix well. Well, actually they do. Too well.

 

[Mark20]

Hydrogen, oxygen and a little sparking does a very good job of getting the Saturn V and Space Shuttle off the ground. All lead acid batteries will emit hydrogen gas when charged. Yep, still a good idea to make the last connection away from the battery!

Sent from my Xoom using Tapatalk

 

[Mark20]

One other thing, all auto makers put together lots of cars every day. If connecting batteries is frying modules I pretty sure they're going to find a solution.

Sent from my Xoom using Tapatalk

 

[The_Roadie]

... I'd be challenging the mechanic(s) to provide a sound explanation of how that happens.

Nah. Wastes your time and annoys the ........ mechanic.

 

[RayVoy]

My guess, your dad probably blow a fuse, or two; and paid $600 to $700 to had them replaced.

Lift the hood and check the ECM/PCM, does it look new?

Was this a dealer, or a "down the street, guy on the corner" mechanic? If not a dealer, he probably does not have the resources to purchase the GM tool required for programming the BCM, nor the new PCM for that matter.


Oh, and btw, the real reason for disconnecting the neg side of the battery first, is so that you can't accidentally ground the metal handle of the wrench when removing the pos side of the battery.
If the neg is disconnected, and the metal handle does touch frame while the wrench is on the pos terminal, there will be no short and subsequent sparking.

 

[Big Al]

So, when I was told always connect NEG first and disconnect NEG last, this is wrong? I was explained that it will always stay grounded if you do it that way and cannot short anything out that way. I haven't changed my battery in my TB but I do connect and disconnect my batteries in my boat once in a while and I always take the POS off first and put it back on after I connect the NEG.

 

[RayVoy]

When your working on your home electrical (120/420), always connect the neutral first and disconnect the neutral last. This will prevent a possible shock (to the human) through the load.
The person working on the house electrical system should be aware that there is a huge potential for a shock from the "hot" side of the supply and use appropriate caution.

The potential for a shock does not exist (for most of us) when working on a 12v automotive system.

However, the potential to ground the positive side of the battery is very high; therefore, disconnect the neg (automotive neutral) first and reconnect the neg last.

 

[Sparky]

Also, have you ever put the wrench on the positive terminal of the battery and touch the chassis of the vehicle with it by accident, while the negative terminal is still connected? Lots of sparks, startled nerves, and a melted wrench that is probably not covered under warranty

Disconnecting negative first removes that possibility.

 

[RayVoy]

Also, have you ever put the wrench on the positive terminal of the battery and touch the chassis of the vehicle with it by accident, while the negative terminal is still connected? Lots of sparks, startled nerves, and a melted wrench that is probably not covered under warranty .

Those of us who have been down the road, will also remove any rings. When the ring gets between the wrench and frame, the resulting sparks and heat are not fun.