clb gone bad
Team Owner
Joined: May 2001
Posts: 87,364
Likes: 1,592
From: Western NY
My reasoning behind modifying my lock plate, goes WAY back, to when the problem with the column lock malfunctions first began to be an issue. A number of discussions on this forum, told people to shake the steering wheel back and forth, in an effort to get the lock pin to retract. That made me think (apparently incorrectly) that the problem centered around the inability of the motor that operates the lock pin, to be able to retract the pin, due to force applied to the pin by the plate. So I simply modified my plate, so there was no longer any side forces being applied to my lock pin.
Racer
Joined: Aug 2015
Posts: 285
Likes: 66
From: Marshall Il
No. The column lock system doesn't work that way at all. Also the 2mph fuel shut off is a part of the NHTSA forced column lock safety recall that was supposed to be done for manual trans C5's It was GM's safety parachute (CYA) to prevent an inattentive driver from driving the car with the column locked. However there are many instances where a dealer tech that didn't follow the recall requirements reflashed the PCM on automatic cars and therefore made the fuel shutoff possible on automatic cars that were never intended to have it. On the 97 - 200 automatics the factory lock plate was replaced with a small diameter lock plate the is incapable if intercepting the lock pin and hence the column can never physically lock. On 2001 - 2004 automatics the small diameter lock plate got installed by the factory.
The BCM is the brains behind the column lock function and unfortunately there is no way to bypass that logic. It senses when you put the key in the ignition and start to turn the key to the start position and it then sends an electrical signal (unlock command) to the lock motor. The lock motor is then supposed to retract the lock pin from the lock plate and once done send an electrical signal (completed) back to the BCM. Since the BCM has no physical way to know if the column is locked or unlocked it uses the "command response protocol" to keep a "lock state" flag. So once the BCM receives the completed from its unlock command it sets the state to UNLOCKED. When you turn off the ignition and remove the key the BCM again senses this and sends a lock command to the lock motor. The lock motor inserts the pin in the lock plate and then sends a completed to the BCM. The BCM should receive the completed and change the state to LOCKED. This is normal operation. BUT, what happens if the lock motor never receives the lock or unlock command because an electrical component in the path between the BCM and lock motor fails or if the battery is low and the column lock relay doesn't function??? GM built some logic into the BCM to attempt to cover those situations. One that was activated on manual trans cars is that the BCM can send a "enable fuel shutoff" command to the PCM if/when the BCM "thinks" the column is locked when it should be unlocked. Doesn't matter if the column can't physically lock because there is no lock plate because as I stated the BCM does NOT physically know if the column is locked or not. BCM relies solely on the "state" information it is keeping. So if the BCM gets itself out of sync with the physical condition/position of the lock pin it tries to err on the safe side and sends the enable fuel shutoff to the PCM. Then when the cars speed reaches 2mph the PCM shuts off fuel and the car stalls.
Since there is no way to defeat the column lock logic in the BCM the after market came up with solutions in the form of the CLB or LMC5. Both those solutions rely on the installation of an electrical/electronic device in place of the lock motor that simply responds back to the BCM lock and unlock commands and is hopefully much more reliable than is the lock motor. The installation of either device requires that the lock pin be retracted and then the power to the lock motor be disconnected. Once that is done the column can no longer PHYSICALLY lock.. Then the CLB or LMC5 peforms the responses to the BCM command and "FOOLS" the BCM into thinking the system is functioning as designed when in actuality the column NEVER physically locks any longer.
The major differences between the CLB and the LMC5 is the physical location they are installed and the voltage they require as a minimum before they no longer are able to function. The CLB is installed under the drivers side knee bolster and AFTER all the factory and NHTSA recall wiring. Therefore failures in certain electrical components after the BCM can result in the CLB never receiving the lock or unlock command and there fore the 2mph fuel shutoff is set. The CLB may require more voltage than the LMC5 and therefore can fail to function. There were multiple versions of the CLB and some have relays inside the box and those require higher voltages than do solid state components. The LMC5 is installed right at the BCM and therefore abandons all factory and recall wiring for the column lock system downstream of the BCM. Additionally the LMC5 is solid state and therefore requires very small voltages to function Generally voltages MUCH lower than required to crank the engine so the chances of the driver ever getting stranded by the fuel shutoff are extremely small.
It is also possible to set the fuel shutoff speed to a high number like 200 or 255. To do this you need access to either HP Tuners or EFI Live tuning software. This again FOOLS the system and the fuel doesn't get shutoff until the higher speed is reached. So you Texas mile drivers might want to set yours to 255.
The BCM is the brains behind the column lock function and unfortunately there is no way to bypass that logic. It senses when you put the key in the ignition and start to turn the key to the start position and it then sends an electrical signal (unlock command) to the lock motor. The lock motor is then supposed to retract the lock pin from the lock plate and once done send an electrical signal (completed) back to the BCM. Since the BCM has no physical way to know if the column is locked or unlocked it uses the "command response protocol" to keep a "lock state" flag. So once the BCM receives the completed from its unlock command it sets the state to UNLOCKED. When you turn off the ignition and remove the key the BCM again senses this and sends a lock command to the lock motor. The lock motor inserts the pin in the lock plate and then sends a completed to the BCM. The BCM should receive the completed and change the state to LOCKED. This is normal operation. BUT, what happens if the lock motor never receives the lock or unlock command because an electrical component in the path between the BCM and lock motor fails or if the battery is low and the column lock relay doesn't function??? GM built some logic into the BCM to attempt to cover those situations. One that was activated on manual trans cars is that the BCM can send a "enable fuel shutoff" command to the PCM if/when the BCM "thinks" the column is locked when it should be unlocked. Doesn't matter if the column can't physically lock because there is no lock plate because as I stated the BCM does NOT physically know if the column is locked or not. BCM relies solely on the "state" information it is keeping. So if the BCM gets itself out of sync with the physical condition/position of the lock pin it tries to err on the safe side and sends the enable fuel shutoff to the PCM. Then when the cars speed reaches 2mph the PCM shuts off fuel and the car stalls.
Since there is no way to defeat the column lock logic in the BCM the after market came up with solutions in the form of the CLB or LMC5. Both those solutions rely on the installation of an electrical/electronic device in place of the lock motor that simply responds back to the BCM lock and unlock commands and is hopefully much more reliable than is the lock motor. The installation of either device requires that the lock pin be retracted and then the power to the lock motor be disconnected. Once that is done the column can no longer PHYSICALLY lock.. Then the CLB or LMC5 peforms the responses to the BCM command and "FOOLS" the BCM into thinking the system is functioning as designed when in actuality the column NEVER physically locks any longer.
The major differences between the CLB and the LMC5 is the physical location they are installed and the voltage they require as a minimum before they no longer are able to function. The CLB is installed under the drivers side knee bolster and AFTER all the factory and NHTSA recall wiring. Therefore failures in certain electrical components after the BCM can result in the CLB never receiving the lock or unlock command and there fore the 2mph fuel shutoff is set. The CLB may require more voltage than the LMC5 and therefore can fail to function. There were multiple versions of the CLB and some have relays inside the box and those require higher voltages than do solid state components. The LMC5 is installed right at the BCM and therefore abandons all factory and recall wiring for the column lock system downstream of the BCM. Additionally the LMC5 is solid state and therefore requires very small voltages to function Generally voltages MUCH lower than required to crank the engine so the chances of the driver ever getting stranded by the fuel shutoff are extremely small.
It is also possible to set the fuel shutoff speed to a high number like 200 or 255. To do this you need access to either HP Tuners or EFI Live tuning software. This again FOOLS the system and the fuel doesn't get shutoff until the higher speed is reached. So you Texas mile drivers might want to set yours to 255.
Thread Starter
Advanced
Joined: Feb 2007
Posts: 64
Likes: 0
From: pappillion nebraska
ok new clb same problem so i checked voltage 14.3 now i look at the bcm and the factory recall has been done the relay is just hanging behind the bcm followed purple wire have the right relay not fixing the relay the lmc5 will be here tomorrow bypass all this noise and this is why you use the lmc5 there is a relay between the clb and the bcm too many things to go bad geeeeez thanks for all your help ill let you know if it works but after all this searching and chasing wires im sure it will. Thanks again
Drifting
Joined: Jul 2017
Posts: 1,365
Likes: 471
From: S.E. Pennsylvania
On the 97 - 200 automatics the factory lock plate was replaced with a small diameter lock plate the is incapable if intercepting the lock pin and hence the column can never physically lock.
I have a 1998 automatic and the column locks each time I park the car and remove the key. It unlocks normally when restarting the car. Would this indicate what is stated above?
I don't think that the car received the column lock recall and there are no aftermarket attachments to prevent the column locking such as CLB and LMC5. Is my car just one of the lucky ones that were not ever affected?
I have a 1998 automatic and the column locks each time I park the car and remove the key. It unlocks normally when restarting the car. Would this indicate what is stated above?
I don't think that the car received the column lock recall and there are no aftermarket attachments to prevent the column locking such as CLB and LMC5. Is my car just one of the lucky ones that were not ever affected?
