Anyone explain this column lock anomaly

silver50

Busy user
I inherited my uncle's C5 that had been unused for years, lying in S Spain. I was paranoid having read about column lock problems before trying to retrieve the car. My father checked the column wasn't locked a few weeks before he and I flew back to meet a car transportation man. Column wasn't locked/locking which was good. So, we got the car loaded on the day and thank goodness we could push/steer the car. Same back in Edinburgh. In my garage and on stands since October 2019. I suspect I've moved the steering wheel a bit from time to time.

Suddenly the column lockedwhen I moved a front wheel a few weeks ago! Connected battery, turned key and it disengaged fine. Phew.

I have to say I didn't think I've seen the dealer recall situation beside the relay, but I assumed nonetheless that is was disabled so was very surprised it suddenly locked. Anyone explain why it wasn't locking then suddenly did..?

i think I too better buy an LMC5. On that note, where might be best to source one? Thanks
 

oelarse

Well-known user
You can order LMC5 directly from Compliants Parts website :)

products


As shown in this link it is possible to remove the motor that run the steering lock but anyhow you need a LMC5 to "fool" the Body Control logic in order to prevent fuel shutoff (from the PCM ) at speed above 2mph
 

silver50

Busy user
Thanks v much. I’ll do something this week regarding getting one.

Anyone able to explain why my column didn’t lock then suddenly decided to? As I say, it disengaged ok but I think I should go ahead and buy the bypass.

I’m assuming my car hasn’t had the recall work (it appearing to currently work ok) Does that affect anything re the LMC5? Do I need to remove the lock plate in the column lock so as it doesn’t mechanically lock? Thanks
 
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oelarse

Well-known user
Here is the description and schematic from the manual and there are several inputs to the BCM logic controlling the column motor .
It is difficult to tell what is suddenly causing the motor to run and engage the column lock without measuring signals with a multimeter



5040

5039
 

silver50

Busy user
Here is the description and schematic from the manual and there are several inputs to the BCM logic controlling the column motor .
It is difficult to tell what is suddenly causing the motor to run and engage the column lock without measuring signals with a multimeter



View attachment 5040

View attachment 5039
Thanks. To help me understand does the column not lock like most cars, i.e. just mechanically locking when you waggle the steering wheel?

I assumed issues were generally all in relation to electronic unlocking.

Going back to my first question. When I retrieved the car in Spain I thought the column would’ve probably locked on us when pushing the car around. It didn’t (but battery was dead)

I suspect it’s working ok just now but I was thinking of pre emptying any problems

Thanks
 
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Stingray

CCCUK Member
I'm pretty sure my C5 used to run the steering lock motor as soon as the ignition key was inserted and similarly when it was removed.

If I recall correctly the official GM fix for a failed column lock is to remove the locking pin and do some reprogramming. I don't think they remove the motor.

My C5s steering lock was worked on at length by the official UK dealer but they couldn't get the GM fix to work. In the end they asked me to get a column lock bypass (as it's not an official part available from GM) which I ordered from Eurovettes for delivery direct to the dealer. Once that was installed they got the car working properly and there were no further problems.
 

Rich

Administrator
If I recall correctly the official GM fix for a failed column lock is to remove the locking pin and do some reprogramming. I don't think they remove the motor.
Probably not relevant in this case but there were several GM fixes depending on whether export/US vehicles, manual/auto gearboxes. year of manufacture. For example the GM fix on my US spec C5 Z06 was some reprogramming and to completly remove the locking plate. Then I had to get confimation for the Club from VOSA that this wasn't an MoT failure as the lock had been disabled!!
 

silver50

Busy user
Thanks for replies, so would I be right that if for example factory fresh and working, when a person turns off and removes key, the column would instantly lock regardless of steering wheel position?

I was thinking about removing the knee bolster to see if there's any sign of recall work (on corvette forum I read about seeing different wiring colours at it)

If the above is correct, it still seems odd my column didn't lock when my Uncle (god rest his soul) last removed the car key.. I'm just trying to understand what was/is going on before rushing to do anything. I guess hopefully just fitting the module would stop any locking and not present any problems.

Rich, how was column locking anything to do with MoT, can't imagine it would be..
 
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Rich

Administrator
Rich, how was column locking anything to do with MoT, can't imagine it would be..
At the time (and I guess it's the same now, but don't quote me) if a steering lock is fitted as standard and if it doesn't work, it is an MoT failure.

As the GM fix resulted in it not working, VOSA agreed that as the manufacturer had removed the lock, then it was a MoT pass.
 

robbiew

CCCUK Member
I would prefer the GM belt and braces method of removing the pin............... just imagine that engaging when in flight !!!! not that i have heard that ever happening, maybe a possibility if you have a major electrical glitch ???
 

Rich

Administrator
I would prefer the GM belt and braces method of removing the pin............... just imagine that engaging when in flight !!!! not that i have heard that ever happening, maybe a possibility if you have a major electrical glitch ???
Except that the removal method only applied to certain models.
I too don't think it ever happened at speed but I guess it was something that GM simply couldn't ignore once the problem was highlighted.
I had it happen to me in a French petrol station on the way to the Le Mans 24hr one year - talk about bad timing. "Excuser moir, monsieur, but my car is broken................."
 

oelarse

Well-known user
In my opinion there is no need to remove the steering coloumn lock motor .
Remove the steering lock motor relay in passenger footwell close to the TDR relay and the motor will never be supplied with any power and never move the locking mechanisme :)
But a LMC5 should always be installed to simulate the locking mechanisme with limit switch to "fool" the Body Control Module and prevent a fuel cutoff situation when speed exceed 2mph at a later point .
 

silver50

Busy user
What is the TDR relay, I think I maybe see wiring going into two relay's above the BCM, is it one of those?

I checked wiring colours under my steering column a couple of days ago and according to corvetteforum.com the colours of wiring to the column lock suggest a factory recall.

I'm still unable to understand why the column wasn't locked when I collected the car but seems to now be locking (thankfully appears to be unlocking OK).

I guess I better get on with getting an LMC5 but I don't really get why the above was the case.
 

oelarse

Well-known user
Here is a photo from my car , passenger footwell above the BCM .

The relay with the purple wire is the TDR relay . The relay on the right which is disconnected is the Steering lock relay .
I disconnected this relay when I installed LMC5 4 years ago .



6125


6126
 

silver50

Busy user
Thanks v much, yes I wondered if one of those was the column lock relay. Mine certainly both still seem to be connected. I thought wiring colours maybe corresponded with those at the steering column but maybe not.
 

oelarse

Well-known user
If you ever get a problem with a no start condition on your car the TDR relay is å good place to start to check if your starter get
it's signal from the TDR relay:)

I did some measurement on my own car showing a guy at Corvetteforum.com how to check the TDR relay , this info is posted here.
 

robbiew

CCCUK Member
If you ever get a problem with a no start condition on your car the TDR relay is å good place to start to check if your starter get
it's signal from the TDR relay:)

I did some measurement on my own car showing a guy at Corvetteforum.com how to check the TDR relay , this info is posted here.
Just checked my lmc5 install and I did disconnect the 2nd relay but I have three relays ! I assume then there's no way the juice can get to the column lock relay with the relay not plugged in ? 99 frc
 

oelarse

Well-known user
Just checked my lmc5 install and I did disconnect the 2nd relay but I have three relays ! I assume then there's no way the juice can get to the column lock relay with the relay not plugged in ? 99 frc
If you look at the schematic in the start of this tread the bi directional motor need both + and - from the BCM to move and when you remove the relay it can only get + or - on one side (right side) due to the removal of the relay feeding the left side of the motor . When you install the LMC5 these wires are relaced with wires from the LMC5. Can't see any possibility for the motor to move :)
 
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