jz, I'm an Electrical Engineer that has worked on cars since I was a little kid. Maybe we should get together on this. I would be glad to send you any of these diagrams, I have all 4 volumes, about 1700 pages per volume. (Some light reading)

I am looking at this and thinking there is a chance the "Body Control Module" might not report trouble to the error codes if the Steering Column Lock Control Module were to be disconnected. My only fear is that the Body Control Module allows RUN/CRANK and it would be just our luck for it to be checking for a unlock signal from the Lock Control Module.

An interesting item here is this system was originally designed for both automatic and manual transmission equipped cars. They have the circuit split and the transmission input comes from either Reverse Switch 1 OR it comes from Park Switch 2. This is huge because it tells me the system can function without the Steering Column Lock Control Module because the automatics have to. Might require some programming or it might just work. One reason I think it is a possibility is because it was set up for the Steering Column Lock Control Module to report problems directly to the Message Center (DIC) and most problems would normally be reported to the main computer, to the error codes, to be extracted when the Check Engine light comes on.

Another interesting point, it appears there are 2 relays in the Steering Column Lock Control Module, each connects to one side of the Lock Motor (Bi-directional). In the de-energized state both of these relays apply a ground to each side of the Lock Motor through their normally closed contacts. If either relay is energized, it puts voltage on the appropriate side of the motor and it flows back through the other relays normally closed contacts to ground. This opens up all kinds of scenarios with 2 relays, 2 limit switches which should ultimately drop the relays out and a motor that needs to complete its cycle in order to terminate the current draw.

Lastly, since this Module is reporting trouble to the DIC instead of the error codes in the main computer (assuming this is true) might be why when the cars are taken in to be analyzed to see what events caused DBS, they can find nothing in the error codes.

Gary

 

This could also be huge because if both automatics and manuals have the same circuitry and the same programming, it means that the only un-common denominator is the actual/physical column lock being in place, putting more credence in the hypothesis that the mechanical aspects of the lock are what is failing. Limit switches are one possibility but I thought of one more as well. The motor drives a "crank" that is supposed to be spring loaded so that the crank can move all the way to the end of its range even if the pin doesn't line up with a hole in the column. Then when the steering wheel is turned so that the pin lines up with a hole, the simple spring tension is what pops the pin in. Now... if the spring mechanism somehow got "hung up" and the spring loading didn't work properly, the motor might be trying to drive the pin directly into the column. If the pin doesn't align with a hole and the spring loading is caught on something in the mechanism, the column lock might continuously try to shove the pin in because the crank hasn't moved to its limit. This could even happen if some motors in some column locks are a little "weak" and the power of the motor is close to the spring tension.

I also don't buy that a fuse would blow because of the current draw of a stuck motor being energized. Fuses are normally designed to be way above the "normal" circuit draw maximum, something like 2x the normal current draw. I doubt a stuck/energized motor will draw enough current to blow the fuse because the max circuit draw would probably be designed around (and the fuse capable of handling) a stopped motor.

I still have never gotten an answer to whether or not a C5 column lock bypass could be used on a C6. I guess the connectors might be different so it wouldn't physically fit but I'm sure the C5 CLB could easily be modified to work on a C6. If we could get our hands on a few C6 CLB's and install them on a few cars that have had numerous DBS episodes, it'd be interesting to see if the few cars that are notorious for multiple DBS's suddenly have no more problems with a CLB installed.

Mike

 

The C5 part will not work. It's feedback switch is either open or closed, but the C6 feedback is 2 resistive values. It would be easy to make one though, but I do not believe this is the issue. I have simulated column lock failure on my car and I have always gotten a message on the DIC and a DTC in the steering column lock module. I don't remember exactly what happened because it was a long time ago, but I believe I got a message on the DIC and the vehicle would still turn off. I got another message on the DIC the next time I stared the vehicle, but the bottom line was that the vehicle still turned off. It also has a different connector.

 

I can understand the reluctance to provide Jeff the information he's asked for, so let me add some validity to this. It was I who put Jeff in contact with our Friend in High Places after asking for similar information from Forum members about 5 months ago. GM really is working on this problem but it's more complex than you might think. They believe there is an interaction between various systems that continually "wakes up" the computer when that shouldn't happen.

Our Friend is at a very high level within GM and has asked that we not reveal his name as he would be overwhelmed with emails and phone calls. He's not playing games, just doesn't have the time to respond to all individuals. I encourage you to become part of the team which will eventually identify and solve this problem for all C6 owners. If you do decided to provide Jeff your information, please include the options you have on your car, such as on-star, radio and mapping options. Also include the circumstances when the battery failed and any involvement your dealer may have had attempting to resolve the problem.

The last note I received from our Friend says:

Bruce: Just a quick update on DBS. GM has assigned an engineer to assist with the rootcause analysis. I have been working with a couple of C5/C6 Reg folks and will probably expand my search in the future to locate a few more cars. Do the complaints seem to have calmed down or are they still as active as they were?

This is a unique opportunity that doesn't happen every day. Good luck to you all,

 

Add some other things discussed:

mirror lights are not supposed to reset, if you push interior light button, they will be on until you push it again. They will turn off for battery saver, but will be back on next ignition

Focus should be on auto/man differences since that is largest split that can be made. Since interior lights, relay 46, etc... they are not likely cause

column lock motor does not have manual shut off, it contacts a switch that sends a signal back to a module that controls it. If it didn't contact that switch, an error message is displayed and a DTC sets.

also, the theory that voltage wouldn't drop all the way to 2V if it was electronic issue isn't a good assumption. If you don't shutdown the car by shifting to reverse, the voltage will drop this far, even though all sources of power are computer controlled.

cigerette lighter is hard wired, leaving things plugged in will kill your battery as well as other things hooked up incorrectly, low jack, radar, etc...

Also, it is important to note that if your vehicle has Onstar, the onstart module will draw current every now and then for 4 days, a stupid dealership may see this draw and think it is a problem when it is not

Here are things that I have verified will cause DBS:
Not shifting into reverse properly
Radar detector, Cell phone charger, etc.. <--depends on load
aftermarket things hooked up wrong, low jack, radar dectectors, etc..
if the ignition switch sticks

My opinion is that it has something to do with the shutdown process and the 2 reverse switches, that one or either isn't beeing closed for whatever reason, or the steering column lock module isn't sending any signal to the BCM. I started to think it could be the signal from column lcok module to BCM, but without it the car wouldn't shut down.

Also, it will be a very difficult problem to solve since it doesn't happen all the time, if someone could easily replicate it, it would be simple to solve.

 

I am still looking at my schematic and I see a symbol in series with the lock motor that could be a thermal protection. If this is a thermal protection, it would be possible for the motor to draw more than 1.5 amps and have the battery last 48 hours. It would cycle on and off (maybe making a clicking sound) and still draw the battery down with the average current draw equal to 1.5 amps.

OttoNP made the statement "If it didn't contact that switch, an error message is displayed and a DTC sets". I think he is talking about the limit switch signal. Here is my question. I believe I hear the lock motor run at the very end of shutdown, after everything has gone dark. I don't see how it could display a message at that time in the DIC since it would already be shut off and if it sets a DTC, and then the next event is a dead battery, will the DTC remain or be lost.

Gary

 

I'm curious how you simulated it. Someone reported they heard the motor run a shorter than normal interval preceding a DBS event. I don't have the car handy right now, but I thought the motor run was towards the end of the shutdown procedure, after the dash goes dark. Is the only message that can come out of the Lock Control Module one that says "service steering lock" or are there other messages. Would a DTC be lost with a dead battery or are they non volatile?

What I guess I'm getting at is if the motor jams and can't get to end of travel, therefore can't report back to the control module to stop trying, and then what if the message and DTC all get lost in the DBS event and then when you start over with a fresh charged battery, all is lost and it's a new day. This would look different than if you simulated a lock failure with a good battery.

Gary

 

According to my schematic we can eliminate one of the reverse switches. Only Reverse Switch 1 connects to the Steering Column Lock Control Module. Reverse Switch 2 must be for the back up lights.

I am wondering how they perform shutdown on the automatics. The initial design called for both manuals and automatics to operate the same. Since they didn't put the Lock Motor in the automatics I wonder if they are still using our Steering Column Lock Control Module to tell the BCM to shut down, only programmed/configured differently so it does not send a signal to the Lock Motor and reports "Shift to Park" to the DIC if not in Park or I wonder if it is an entirely different module. It would be nice to install one of these units from an automatic and feed it with the in reverse signal (in place of Park). This would make our MN6's operate just like the automatics, no more Lock Motor and no more DBS.

Gary

 

Great stuff guys, let me start by saying I too am an EE and worked 11 yrs as a design engineer in automotive, but I changed industries 4 yrs ago. I completely understand the chemical and electrical characteristics of batteries (charging systems was one of my responsibilities and I worked closely with Johnson Controls for many years).

Mike, Gary and Otto, you guys have provided great info - I have a few comments...

Mike: fuses can most definitely blow due to motor stall in a circuit. No engineer in his right mind applies a fuse that can take 2X the circuit draw. Again, fuses are there to protect the harness. That's why thermal protection is applied (typically bi metal breaker). If some person continually tries to roll down their frozen window, the cb will trip instead of the fuse blowing. Prior to Gary's info, I have been continually asking about the circuit. I do concede that the motor in the CL is probably very small, but it should still have some thermal protection somewhere.

Otto: A battery that is reading OCV of 2 will not energize the relay that engages the motor. And the SCLCM should be dead. Most automotive electronics die below 9v (at least they used to). It would be interesting see what systems drop out and when.

Gary: Thanks for the circuit info. I do have a question with regards to the BCM role...is this an input or an output. I initially thought it an input required to allow the lock engage, but Otto posted that the signal comes from the SCLCM (limit switch) to the BCM and then the BCM will set DTC if no signal is present. Let's assume this is how the system operates then...

We basically have 2 choices of failure mode...

1) Motor never shuts down during lock cycle

2) CL system shuts down, wakes up cycles, shuts down, etc.

Case one: B+ is present to module, Ignition goes low, reverse switch signal is received, relay energizes and motor travels to lock. If the limit circuit is not functioning, the SCLCM would continue to try to lock the column, the BCM may or may not get it's signal. Here is where thermal protection should come in. Typically the high side of the relay would have this. Assume it's there somewhere...then the system would in effect cycle at the rate of the thermal protection. This would cause a drain on the system that would last until the voltage was too low for the relay to stay energized. This can happen. My problem is how the battery drained down to 2.x volts. The relay should have dropped out before this much drain occurred.

Case two: Requires the SCLCM to wake up after being shut down and think it needs to lock. I read this as needing a state change at the ign input since the reverse switch input is dead after good shut down has occurred. If ign sw is common to both MT and AT, then everything again points back to case one, unless something else can happen that can wake up the SCLCM.

Your thoughts? and btw, those resistor values are strange. I'm assuming (dangerous, I know) that they are being used to bias transistors that energize the relay coils.

Gotta go, will be back later tonight.

Again, to all of you guys...Kudos... now we are getting some good info. At least I now have somewhat of a picture of the system.

Jz

 

This is a quick update to the forum since I started this original thread several days ago. I have received about 15 names and VIN numbers and they have been passed on to our 'engineer friend in high places'. One or two of you have already been contacted and you now know this is a legitimate request. Again those who frequent the C5/C6 Registry already know this is legit and are familiar with the engineer in question. Thanks to everyone who sent your information. A small team of engineers are now being assigned to make a serious effort to finally solve this dead battery issue. You will be contacted soon as they are trying to zero in on what options the cars may have that are experiencing the problem and are going to ask you to track your experiences so that they may establish a pattern. Again, the more owners they can contact the better since that will give them a much better croos section of car options etc. I am sorry that there are a few members of the forum that are suspicious of this request becuase these engineers are working behind the scenes to find a fix for those of us who have experienced the DBS problem. If you still want to participate in getting a fix for this awfully aggrevating problem you can still send me you info at the address in my first posting.

Thanks again to all who have responded.

Jeff Duplak
Reading, PA.

 

Thank's Jeff for your help.

 

I have dug up lots of good stuff today out of the shop manual.

The fuse for the BAT supply for the Ignition 1 Voltage is a 10A. The fuse for the BAT supply for the Steering Column Lock Control Module including the Steering Wheel Theft Deterrent Lock which is mounted right beside it on the steering column is 10A also. This unit includes the motor by the way.

I have found a symbol near the Lock Motor which I believe to be a thermal protection for the motor.

Here is the best for last. When a DTC sets in the Steering Column Lock Control Module it will also send a message to the DIC saying "Service Column Lock Now" This message will only go away on its own if it sees 50 consecutive ignition cycles with the malfunction cleared. There are 3 things that will set a DTC and cause this message.

1. The Steering Column Lock Control Module (SCLCM) receives a Lock command from the BCM but the shifter is not in the PARK position or there is a short or an open on the wire to the Park switch. (One time will set it)

2. The SCLCM unlock relay circuit gets short to ground, open or short to voltage on it. (One time will set it)

3. If the SCLCM does not get a valid feedback from the motor. Here is the kicker.......for this to set a DTC, it has to happen 5 consecutive times. This means that an occasional event will not be reported. If the motor binding half way to end of travel is what is causing DBS, by design, the DTC will not be set. I think they had so much trouble with this locking motor in the C5, they wanted to cut it a little slack so people would not be randomly getting the dreaded "Service Column Lock Now" message on the DIC.

Gary

 

As far as the battery going down to 2V, I have to agree that any relay except latching relays (I don't see why it would be a latching relay in this circuit) should fall out by 50% voltage. Electronics should die at around 9-10 volts. I do know there are 3 relays in the SCLCM which are, lock enable relay, lock relay and unlock relay. One of the signals to activate the lock and unlock comes from the BCM. Signals also come to the SCLCM from the ignition switch and the Reverse Switch 1.

Although I can't explain it, I have to agree that the battery is run all the way dead over time. My first 2 DBS events I didn't notice it for many days and when I unhooked the battery it was completely dead and took the charger a long time to even come off the peg. After that I started checking the flashing light on the dash twice a day and on day 2 it went out so I unhooked the battery and I didn't think to measure it but it sparked and was not all the way dead. Can't get there from here on why, but it is so.

Do you suppose these so called relays are really SCR's and can stay gated down to less than a volt. Someone did report a clicking sound. Maybe that was the thermal protection for the motor going on and off. The motor and SCLCM should be located on the column up by the steering wheel.

I found 3 more situations that set the DTC on the SCLCM. One has to do with the password not matching on the FOB, one is a short, open or short to voltage in the lock relay circuit and the last is a biggy. It detects the SCLCM is locking the column but no command has been received from the BCM. This last one of the 6 total is the only one that also reports it back to the BCM. The rest all stay local. I guess that would be a baddy.

If you read my early post today I am trying to figure out what is used in the automatics and would like to copy this and remove the Lock Motor and the SCLCM. I'm trying to figure out if they have a different type of SCLCM or just use ours configured differently. The book is a little confusing, they are talking about DTC's coming from automatics and not MN6's and on a different page they have it set up for both automatics and MN6's and on a third page shows the SCLCM and Lock Motor labeled for the MN6's but never show it again for the automatics. Very crude manual, needs a lot of clean up.

What I wouldn't give to have a half hour conversation with the lead GM engineer that designed this circuit.

Gary

 

Gary, I'm guessing the symbol you are seeing should be a line arcing away from a connection. That used to be a universal representation for a circuit breaker which is just thermal protection.

Item 3 above is interesting. So, if the motor feedback is not valid (for whatever reason), a DTC will be set after 5 consecutive times. 5 consecutive times of what? Ignition cycle? All it would take is ONE time and the circuit would go into a drain cycle modulated at the rate of the thermal protector. I would expect there to be a secondary check, like a timer circuit (watchdog timer) that would time the lock cycle and check for valid input from the motor. If this was not received within the expected cycle, the relay is de-energized.

How can they expect an invalid feedback condition to happen 5 consecutive times unless there is another check (watchdog timer). Otherwise, the vehicle will drain on one occurrence.



Someone's post earlier stated something to the effect that GM is trying to find what is waking up the unit. I don't see with the info I've received from you how the vehicle could possibly wake up without there being a state change at the ignition input. Ignition on, or acc on and vehicle goes to unlock. Ign off or in RAP, reverse sw signal, and BCM signal and vehicle goes to lock. Could the BCM signal possible wake up the box? What is the criteria for the BCM to send the signal and what is the signal - this should be in the service manual.

Later,

Jz

 

Just a quick note to THANK YOU all who are working on this! You are a blast to watch and I'm positive you guys will figure this out, along with the GM guy who's working on it! Thanks!

 

Though I have never experienced DBS, I agree with Vapour, many thanks

In the meantime, I just recieved my Priority Start and installed it a few minutes ago in the event this effort peters out or otherwise fails.

 

If the limit switch is the only way to de-energize the relay coils (do not believe they would use scr's), then without a doubt a bound motor could kill the battery. I do have 3 issues with this...

1) It's difficult for me to believe that more if any people did not notice the motor running.

2) Why does the batt drain so far?

3) If the motor is bound or the limit switch is out of place to pull the resistor to ground (or any other cause of the invalid feedback), then what fixes it? Why isn't it in the same condition after the battery is charged?

Any thoughts from you guys?

Gary, where in the circuit is the lock enable relay? This may come into play.


Jz

Jz

 

I actually thought about this one before. There is a good chance that the condition is still there when the battery is charged. As long as the charger has enough juice to supply more amps than the drain, the battery will eventually charge, you'll start up the car, and when you start it, the computer probably signals the column lock to back out. At that point, you've interrupted the cycle.

What I saw on my DBS supports this. When I discovered 2.4 volts on the battery, I connected my 6 amp charger and the needle pegged on the charger (above 8 amps). It was so bad that the charger was overheating and cycling on/off/on/off. I then decided it might be better if I disconnected the battery from the car and just charge the battery stand-alone. When I did that, the needle came down to about 7 amps and the battery eventually charged back up. In any case, it did look like the car was causing some additional draw over and above what the dead battery was pulling, lending some evidence that maybe the drain is still there... and maybe it only goes away when you crank it up after the recharge.

Mike

 

If you want to know the options on the DBS cars, that info is here too in this thread. Might not cover everything, but it's good data from a lot of people.

Mike

 

To answer some of your questions:

The limit switch has nothing to do with de-energizing the motor, the limit switch is just a signal to a IC controller with logic that will de-energize the motor even if it the limit switch is not contacted.

As far as relays latching, I played around with a relay, same kind as relay 46, and some AAs. I found that it will latch consistantly at 4.5 V and sometimes at 3 Volts. I had to take it apart and watch it since it doesn't make nearly as loud a sound. With 3 volts it will stay latched everytime I tried it. My earlier comment about 2 volts was mainly to say we shouldn't only focus on mechanical causes, though I agree I could see the logic. But, if you think about like this, the ECM and many other modules, radio, etc... have a hard power line (fused) to the battery, they receive some kind of class 2 message to change power states to off, on, RAP, etc... and as the battery drops they won't receive this, who knows what happens inside the module as the voltage drops down. Also, since most of the logic uses 5 volts signals I can see how it can get that low. All the times my vehicle was left out of reverse killed the battery down to the lower ranges mentioned above. Also, the vehicle has a normal drain that is present all the time.

On to the 2 reverse swithes, neither power the reverse lights. They both are signals, one is a signal to the BCM and the other a signal to the lock module. They are both powered by the BCM. The switch that is connected back to the BCM signals when to turn on the reverse lights and also is a signal for the BCM to send message to the lock module to lock the column if vehicle is turned off. The signal to the lock module is a redundent check to make sure the vehicle is in reverse before locking the column, only the switch for the BCM must be closed for the vehicle to shutdown. If the other switch is not closed, a B0005 DTC will set. Also, the DTC I mentioned before set in the lock module, not the BCM. Also, not that a B0005 will set in the BCM if you drive too many times with parking brake on. You can see the status of both of the switches using data display on a Tech II.

The difference between manual and automatic would make it difficult to convert yours. The BCM is programmed differently and the park signal somewhat takes the place as the reverse signal. An automatic will also kill the battery if you don't shift back to park when you turn it off. Automatic does not have a column lock or lock module, used brake instead of clutch, etc... If you wanted to retrofit, best bet would be to try to make it like 2006 manual, which do not have lock or lock module. In this case, my complete guess is that you could just reprogram BCM and remove lock module, probably leave column lock in, but make sure it is unlocked . It is a very not fun procedure, to remove it requires special tools.

On to my testing....

basically I had a extra column lock that I took apart. The lock module is easily accessed by taking off the IP and the cluster, it is right behind it on the right. The column lock plugs right into it. I unplugged the one on the vehicle and plugged in the one I took apart, because it was taking apart I could make the limit switch show whatever position I wanted, including open. It was a long time ago, so I may not remember it exactly. I know that I tried not changing the limit switch and the motor would indeed time out after maybe 10 seconds. I tried a lot of things and never came across any kind of weird response, the fault detection seemed pretty good and the vehicle shut off in every scenario, as long as the reverse signal was sent to the BCM. Also, the motor is indeed thermally protected. I had a shunt hooked up to the battery to check for any draw.

I really wouldn't worry about it if it hasn't happened to you, I wish my car would do it, I have been super curious about this issue ever since I first read about it on the forum...