Originally Posted by rustyroo

Sorry I left out the detail that I have the manual transmission.

I'm a bit confused between what digitaloutsider and 8vette7 wrote. I can turn the steering wheel 180 degrees or more without the key in the ignition. That only moves the wheel a bit but I think that is what is meant. Digitaloutsider wrote that if I can turn the wheel, I need to do the LMc5 installation. 8vette wrote that if the wheel can be turned, then the LMC5 mod has likely been done. Please clarify. Thanks!

Originally Posted by 8VETTE7

If the 04006C variation of the GM column lock recall service was done on the car there are two ways to know it has been done. The first way is by getting a copy of the GMVIS for the car and looking for column lock service done AFTER March of 2006. Even if that variation was done, there is a possibility that an earlier variation of the recall was also done that sets the fuel shutoff to 2mph when the BCM thinks the column is locked when it should NOT be. The GMVIS will also reflect that information about an earlier column lock recall service. BCM has NO PHYSICAL way to know if the column is locked or not. It relies on a command acknowledgement protocol with the lock motor (or a CLB or LMC5) to keep track of whether its lock or unlock commands were properly acknowledged. With the factory OEM column lock system in place it is VERY easy for that protocol to get out of sync and result in the 2 mph fuel shutoff being enabled which shuts off fuel to the motor once the vehicle speed reaches 2mph. The 04006C variation did not flash the PCM for the 2mph fuel shutoff but earlier variations of the recall service did.

The second way to know if the 04006C variation was done is to listen for the lock motor to operate. When you insert the key into the key cylinder and just begin to turn the key you will hear a soft BZZZZT coming from under the plastic housing surrounding the steering column. That is the lock motor retracting the lock pin. A similar sound occurs when you shut off the engine and remove the key from the key cylinder. That is the lock motor extending the lock pin. 04006C replaced the lock ring that the lock pin intercepts to lock the column with a small diameter lock ring that is incapable of intercepting the lock pin. Additionally the legendary GM K Harness was placed in series between the lock motor and the BCM. It is the K Harness that actually responds to the BCM lock and unlock commands and not the lock motor if 04006C has been done. The K Harness is well known for frying when the battery voltage goes low. This results in a failure of the command acknowledgement protocol and if the PCM has been flashed for the 2mph fuel shutoff the driver can be left stranded by a car that starts but cannot be driven faster than 2mph... Here is a pic of a fried K Harness:




If either a CLB or LMC5 is installed then the lock motor gets disconnected with the column in the UNLOCKED state and the replacement device plugged in to receive and respond to BCM lock and unlock commands. Basically these devices are fooling the BCM into thinking the column lock system is functioning normally when in fact the lock motor is no longer in the circuitry. Hence you will not hear the lock motor operating. Since your column does not lock with NO KEY in the key cylinder you can assume that either a CLB of LMC5 is installed if the lock motor cannot be heard operating..

In my post above I provided a link that shows what a LMC5 look like. If one is installed it will be in the passenger foot well behind the toe kick and next to the BCM (large silver box to the left of the IPC fuse box) and look like the image at the link above.

To determine if a CLB was installed you need to do some lower dash disassembly on the drivers side to look for the CLB module.




If I owned the car I would order and install an LMC5 and do the "brown wire mod" described as optional on page 2 of the LMC5 install instructions. Do it at LMC5 install time and avoid having to go back later.

The LMC5 abandons all factory or recall wiring downstream of the BCM (as well as CLB if one is installed) so it has positive control of acknowledging the BCM lock and unlock commands to prevent the owner from being stranded by the GM C5 column lock FUBAR....

Originally Posted by rustyroo

Thanks so much for your kind response and wealth of info on the topic. I'm sure it will be a big help to others that are just buying a C5 and don't know about this problem. The LMC5 mod was done on my Vette. It was hard to find as they had it tucked in well behind the wires. I knew it was done because it had the black grounding wire attached to the BCM and the right relay above the BCM box had been removed and tucked away. I don't know if the brown wire mod had been done or not because my eyesight is poor and I gave up looking for it. Sounds like the instructions for it was included in the LMC5 package which I don't have. Assuming mine doesn't have the brown wire mod, is there any reason to pursue it given I'm not getting any codes? Thanks again, muchly appreciated!

Originally Posted by rrwirsi

Here are the LMC5 instructions.