cuspid

I received from Dept of transportation sb623665, it says " Gm engineering has expressed concern that the use of these column bypass systems may adversely affect the body control module. It is believed that the electrical circuit used in these bypass systems may not draw sufficient current to prevent the oxidation of relay contacts within the body control module.This should not be considered a warrantable defect of the body control module. This is Dave Piecy, Brand Quality Manager for Corvette. If there are any questions I can be reached at 810-575-5339. Dated july 10,2001. For 97,98,99,2000,2001,2002 corvettes. Anybody know about this? What does the body control module do? :eek:

carpe dm

Yes, I have heard of this. C4C5 Specialist has talked of it too. I'm on the road, but when I get home (where my manuals are located) I am going to see if the module can be pulled and the contacts cleaned. Mine has been in for almost two years and I suppose it is in need of TLC. :)

sandyg

What is a column bypass? That is one that I missed.

Patches

He probably means "column lock bypass", the aftermarket device that prevents your steering column from locking by disabling the steering column lock. You have one in your sig. :)

Recently, C4C5 Specialist posted that the CLB could potentially damage the BCM due to an insufficient voltage condition created by installing a CLB. This is certainly bad news for those of us who've installed one.

I'm debating whether to pull mine off my '02 and risking a column lock. '02 owners have already reported column lock incidences on this forum.

Great! Damned if we do - damned if we don't. :rolleyes:


[Modified by Patches, 11:01 AM 7/27/2002]

pewter99

How did you get this letter?

Grumpy

:confused:

66ImpalaLT1

Cars under the column lock recall campaign do not need the bypass. GM put a relay in the circuit which will still operate and fool the BCM even if the column lock solenoid is disconnected.

Someone recently posted the procedure on the forum.

Eric

Oh Cool

I wonder if one the the CLB Vendors can shed some light on this topic?

NassBlue

:confused:

My BCM was replaced a month ago because the car would not start... I have the CLB installed, I hope this is not true :confused:

CarlB

NassBlue,
Could you share some details, this is getting worse by the moment.
CarlB

c4c5specialist

Hi there,
Corvette engineering has been dealing with this issue for many years .
Plain and simple, the 'letter' posted above is actually a SERVICE VME, which is issued to Corvette dealers, to assist in situations that arrive with C5.
This is supposed to be internal to service personnel, thats it.
We talked about this many months ago, with really noone being worried.
Why now is there so much concern?????
Plain and simple, this has been an issue for a while, and was known, contacting our brand quality manager, for an issue long known, and addressed, would be a little late.
Besttoall, c4c5 :chevy

55SUX

I have heard of this warning but have yet to hear of anyone that actually had this problem with the BCM. I've had that CLB on my 99 for a long time and never had any problems. Anyone actually have this problem with the BCM? And was it definitely due to the CLB or something else with the BCM. Seems like it would be real easy for the dealer to speculate that it was due to the CLB without having any proof.

Also, I've heard conflicting reports on whether you can just unplug the column lock after the GM fix. Any confirmation?

Z06 Mike

We can put a man and a dune buggy on the moon. (Glad GM didn't have its' Column Lock on it!!)....but we cannot fix this simple, yet agonizing and potentially dangerous problem. :mad :mad

6spdNavy99

I've heard this too, but MN6 only. It must be done with the column unlocked and the engine runnning. I haven't had the guts to do it yet. Here is the thread on the issue: http://forums.corvetteforum.com/zerothread?id=338674

ersatz928

This is my theory : I believe this "too low a current from a CLB" is actually a problem with the existing colum lock power relay, NOT the BCM itself. The BCM has two types of outputs associated with the colum lock. The first, drives the coil of the colum lock power relay (located next to the BCM). This power relay then closes the path for the 12V supply to the BCM, and then the BCM continues this current path (thru the 2nd output) to the colum lock actuator motor itself. This second BCM output is what changes the applied voltage polarity to the motor, one polarity for LOCK, opposite for UNLOCK. The power relay contacts could become intermittant (actually a high resistance condition) due to the application of the significantly lower current required by a CLB. This relay is cheap and easily replaced. This relay contact failure condition can occur when too low of a current is switched thru relay contacts which previously had carried a higher current (the colum lock motor). The higher current provides a self cleaning action whenever the relay contacts make and break the circuit. This contact cleaning action may not happen with the lower current of the CLB. Eventually the contact resistance gets so high that the CLB fails to actuate, and then it no longer fools the BCM, and you get the Service Colum Lock and 3 MPH engine cut-off condition.

In any case, if this problem is real, a 10 Ohm 1 watt resistor can be wired across a CLB, so that enough current is drawn to keep these contacts functional. This may even "fix" a relay where the contacts are oxidized, a few activations should clean them up.


[Modified by ersatz928, 4:55 PM 7/29/2002]

Charlie LI NY

you say to place a 10 Ohm 1 watt resistor across the CLB. You definetly mean across the CLB connection not inline with the bypass?

Smoke-N-Shot

This could be a troubling issue with some installations... I think many will be asking "Now What"?

Z06 Mike

We can put a man and a dune buggy on the moon. (Glad GM didn't have its' Column Lock on it!!)....but we cannot fix this simple, yet agonizing and potentially dangerous problem.
_______


I say it again...GM needs to fix this once and for all! How many of us hold our breath everytime we start our 50K+ cars???

ersatz928

Put the 10 Ohm resistor across the CLB, from Pin "C" to pin "D" of the four pin connector. The resistor will draw additional current when the CLB is pulsed by the BCM, keeping the relay contacts clean.

For what its worth, after getting home and looking at the colum lock schematic in my Service Manual, my above posted circuit description is not quite right, but the reason for the relay contact failures and the 10 Ohm fix is still valid. The correct description is that the colum lock "control" relay connects and disconnects the colum lock motor from the BCM polarity reversing outputs. This relay is there as a safety interlock which prevents the BCM from changing the colum lock position "accidentily", such as can be caused by a single hardware failure or operating software glitch of the BCM. This relay actually shorts the colum lock motor power input wires together when the lock motor is not activated, also preventing motor movement (due to vibration) thru an electromagnetic braking effect of the short.

I'm sure this is more than anyone wanted to know!!!!!


[Modified by ersatz928, 9:14 PM 7/29/2002]

George Cooper

ersatz928-

Two questions:

1) Have you or anyone else actually done this?

2) Does it matter what kind of resistor (carbon, metal film, power type)?

Thanks for the help!