This is an attempt to compile all the Column Lock Information into one place. If there are errors, please contact me so I can make corrections. With all the recalls, there is a lot of confusion, questions, anxiety, and threads. Hopefully this will be helpful to our forum readers.
Q What is the symptom of failure?
- GM installed a Steering Column Lock mechanism on all 1997 - 2004 manual (MN6) cars and on 1997 to 2000 automatic (A4) cars
- There is a GM recall for this problem on affected models and years
- It is one of the most problematic issues that we C5 owners deal with
- It can happen to you if you have a pre-2001 A4 without the recall or CLB installed OR any year MN6 or Z06 car without a CLB installed. Age or mileage makes no difference.
- Low battery voltage seems to aggravate and sometimes cause column lock failures
A Your steering wheel will not unlock and the DIC will display an error message "Service Steering Column Lock". Your owner's manual will instruct you to have your vehicle towed to the nearest GM dealer for repair.
Q What exactly causes this failure?
A When you insert your key into the ignition and turn it to the ON position, the BCM (Body Control Module) sends a command to your Column Lock Motor to "unlock" and then checks a status line to ensure that the steering column is unlocked. If it gets the wrong status, it will display an error message as mentioned above. It can be caused by ECL (Electronic Column Lock) mechanism failure and occasionally by low battery voltage, which sometimes confuses the BCM.
Q Can anything be done to unlock the steering column once it has locked up?
A Sometimes; turn the ignition OFF and REMOVE the key. Shock your lock motor actuator assembly by jerking the steering wheel against the stops. Re-insert your key and try again. Also, if your battery voltage is low, charge your battery or replace it.
Q If my battery is discharged and I jump it to get the engine started, the alternator is now charging shouldn't the column unlock?
A NO; The whole unlock sequence occurs before you ever turn your key to start your engine. If the battery is too low, you will probably have trouble with your column lock. Several folks have replaced their battery and the column lock problem has never occurred since.
Q Does this problem affect both A4’s and MN6 vehicles?
A Yes; however if you have 2001 or newer A4
car, the ECL lock plate has been replaced.
Q What years are affected?
A Pre-2001 A4 cars and all MN6 or MN12(Z06) cars.
Q Is there any solution for this problem?
A Yes; have the recall done if you have an A4 car or install a Column Lock Bypass (CLB) on MN6 & MN12 cars BEFORE
the problem occurs. Once it fails, you may not be able to fix it without GM repair.
Q Where can I purchase a CLB?
A They are available from several of our forum vendors such as:
and Corvettes of Houston
Q How much does a CLB cost?
A Typically about $49.95.
Q Is a CLB difficult to install?
A No; very simple (less than an hour) by following instructions. See this link for help: http://97vette.com/howto/columnlock/index.html
Q Can I build my own?
A Yes; if you have soldering skills and $20 in parts, you can build your own in about 1 hour. See this link for info: http://shelor.net/Z/CorvetteForum/Cscokd/
Q Are there other alternatives?
A Yes; there is a GM "Harness K" GM part no. 89023816 (was 88952427), which GM installs as part of its recall; it costs ~ $85.50.
This harness is installed leaving the Column Lock Motor active. However the Lock Plate inside the steering column must be removed or replaced. If installing on a MN6/M12, do NOT connect up the column lock motor harness side (C207 female receptacle).
Q What exactly does the GM recall do?
A The following details were provided by forum member "TopCat" and should prove very helpful:
If your car has NOT
been previously serviced under Customer Satisfaction Campaign 01044 or TSB 01-02-35-008, the GM recall outlines a 3-step process:
- Installation of wire/relay kit under the passenger footwell
- Re-program your PCM
- Jack up your front-end with your wheels off the ground to do a functional test with the Tech 2. If any scraping, clicking, etc. is "heard" or felt by the service technician during the functional test, then the locking plate, retaining ring, and nut are supposed to be replaced.
- If a CLB or a Harness K is found during this process (the recall specifically mentions this), it is supposed to be removed.
Here's a very informative link that describes the actual GM service instructions including electrical diagrams:
Chevy Dealer Service Bulletin
For MN6 & MN12 cars only:
1998 built through 5/25/98
1998 built on or after 5/28/98 (CSC 01044 was performed)
1998 built on or after 5/28/98 (CSC 01044 was not performed)
Install wire kit (part#88952428) and reprogram
1999-2000 and CSC 01044 or TSC 01--02-36-008 was performed
1999-2000 and CSC 01044 or TSC 01--02-36-008 was not performed
Install wire kit (part#88952428) and reprogram
For A4 cars only:
Install wire kit (Harness K), remove and discard lock plate, install the "cam orientation plate" where the lock plate previously resided. No PCM flash required.
No Change Required - they didn't install the Electric Column Lock (ECL) on those years, in the U.S., after experiencing so many problems.
Q I have an A4 car; what should I do if I get a recall notice from GM?
A This is a personal decision. My advice is to have the recall implemented. They will service your car per the above recall discussion. After the recall is implemented on A4's, you should be able to turn your steering wheel with the key removed.
The only anti-theft mechanism now will be your A4 transmission will remain locked until the key is ON.
Q I have a MN6/M12 car, what will the recall do?
A IF you have a MN6/M12 car, the recall does NOT disable your column lock motor. It simply re-programs your PCM to guarantee your fuel is shut off at speeds above 2 mph so you cannot drive your car with the steering column locked. The column lock failure can still occur at any time and you will most likely be stranded somewhere needing to be towed to the nearest dealer for repair when it occurs.
Q If I have a MN6/M12 car, what should I do?
A Again this is a personal decision. Advice is to install a CLB and ignore the recall. It does nothing to prevent the problem from occurring.
Q If I have a MN6/M12 car, will the GM recall re-program my PCM and affect my tuning?
A Yes; See description of recall instruction above. There are several horror stories related to this. Most folks with tunes do NOT
allow the recall to be implemented.
Q Exactly how does the steering column lock mechanism work?
A The steering column lock unit consists of a 12VDC motor, a worm drive gear, a locking pin, and a micro switch which is activated by the lock pin screwing down thru a lock plate with holes or slots in it to lock your steering column.
Q Can the steering lock up while driving my car?
A There have been a few rumors of this. The only way this is possible is if the BCM should fail sending a "lock" command to your lock motor. There are some fears that the lock motor can partially retract but not all the way so that the lock pin could engage the locking plate later while driving. This is highly unlikely due to the mechanical micro-switch, which detects when the lock pin is completely
retracted before sending the "unlock" signal back to the BCM.
The worm gear on the motor turns a gear on a threaded shaft that "jacks" the pin assembly in the direction determined by the motor.
link was lost
[I]The second picture shows the pin/jack assembly, laid out
link was lost
Finally, the last photo shows the micro-switch that is either opened or closed by the body of the pin assembly:
link was lost
Q If I install a CLB, can the steering column lock up accidentally from vibration or shock?
A Highly unlikely; the lock pin is driven by a worm gear drive on the motor which can not move without the motor turning as well.
Q What exactly does the CLB consist of?
A A small module that plugs (in place of your Column Lock Motor) into C207 (male pin side) consisting of a 4-wire harness to your BCM. The CLB consists of a 12VDC-latching relay. Connections are:
Q I still get the "Pull Key and Wait 10 Seconds" message and "Service Steering Column Lock" message? What do I do now?
- Purple wire: from BCM = UNLOCK
- Orange Wire: from BCM = LOCK
- Black Wire: Ground
- Green Wire: to BCM = OPEN is locked; CLOSED (grounded) is unlocked. This status line is pulled up to +12V thru a resistor inside the BCM module.
A1 Sometimes the latching relay in the CLB can get out of sync sending the wrong status to your BCM. This has happened to a few folks even with the CLB installed. The CLB latching relay gets out of sync with the BCM possibly due to shock, vibration or relay contact bounce during switching which confused the BCM. The CLB does not physically know which state it should be in; it only switches from one state to the other when it receives a signal from the BCM. The BCM can be reset by pulling Fuse 23
and waiting 10 seconds.
A2 Check to make sure Fuse 25 in passenger footwell is good.
A3 Verify the black wire to your ECL or CLB is grounded (zero ohms resistance).
A5 Verify the green wire to the ECL or CLB is shorted to ground while in the "UNLOCKED" position and pulled up to +12Vdc while in the "LOCKED" position.
A6 If you get the "Pull Key and Wait 10 Seconds" message but no "Service Column Lock" message, it can sometimes be a symptom of your security system and related to your key pellet.
Q What can happen then if my CLB gets out of sync?
A Your DIC will display "Service Steering Column Lock" error message; your steering wheel will not be locked; if you own a 1997-2000 C5 that has not had the recall implemented; you should be able to drive your car normally. You must reset your DIC each time you start your car if you are annoyed with the error message. IF you have a newer C5 (2001-2004) OR you've had the recall implemented, you will NOT be able to drive your car because the fuel will be shut off at speeds above 2 mph.
Q When I purchase the CLB, what is the extra harness with the cigarette lighter plug used for?
A This is simply to help you unlock your steering column with the ignition key removed. It is used one-time only just before you install your CLB. It connects +12V to the purple wire on the Column Lock Motor to unlock your steering column. Another method is to turn on your ignition key, verify that your steering wheel is unlocked, then disconnect the wire harness to your lock motor. You will need to reset your BCM after doing this to clear the error that this will create.
Q I had the recall done and now after a few weeks my car is getting the dreaded “Service Column Lock” error message and I can’t drive it because the fuel is shut off. What should I do?
A You have the following choices: 1) return to the dealer and make them fix it; 2) A4 cars - replace or remove the Harness "K" assembly; 3) remove the recall mods and restore to original; 4)MN6/M12 cars only - go into your passenger footwell, locate the relay added by the recall mod, remove the relay altogether and bypass the circuit as described below (my choice).
Q What happens when I install an aftermarket CLB and it doesn’t work?
A You probably have the GM recall mod (mentioned above) installed on your car already. This could happen by GM installing the mod at the factory, or the recall mod was already completed by you or a previous owner.
Q How can I tell if I’ve had the recall mod?
A1 If you have an A4 car, can you turn your steering wheel freely while the ignition key is removed? If so, you probably DO have the recall mod.
A2 For all cars, you can inspect your wiring by removing your knee bolster under the driver's side. Inspect your column lock harness. If the four wires in your ECL harness are Orange, Purple, Green, Black
sides of the connector, then you DO NOT
have the recall mod installed. If you have White, Purple, Green, Black
on either side of the connector, then you DO
have the recall mod.
Q Why is there sometimes a conflict between the recall mod and my CLB?
A For MN6 and M12 cars, the recall mod added a second relay (different from the Harness K which is the GM version of the CLB) between your BCM and your ECL in series with the orange (LOCK
) wire. This is to safeguard against a spurious glitch from ever locking your ECL while you are driving (clearly GM is paranoid now). The problem is that this second relay is causing a timing glitch, which resets your CLB immediately after it switches states. The reason it works with your stock ECL is because your ECL motor (being mechanical and slow compared to solid-state logic), is immune to these timing glitches whereas the latching relay inside your CLB sees these glitches and reacts to them.
Q For MN6/M12 cars what can I do if this situation occurs?
A Go into your passenger footwell. Remove your BCM and locate the recall mod relay, remove it and add a jumper wire between the white wire (pin 30) and the orange wire (pin 87). Note that there are two orange wires, so make sure you get the right one!
Q Can CLB modules fail?
A Yes; we have occasionally heard of a CLB failure.
Q If my CLB fails, will it damage my BCM?
A Possibly, but extremely doubtful; there have been some claims of this happening, however after personally researching it now for the last year and talking with many forum members, I have yet to see where a BCM actually experienced electrical damage. GM put fuses into their designs to protect the BCM from short circuits and failures.
Please send me comments. Thanks!