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Thread: C5 steering column lock, NO BS, just details and information

  1. #1

    Default C5 steering column lock, NO BS, just details and information

    This thread is going to cover the Corvette steering column lock system from 1997-2004. I am populating tips and diagnostic process that I have utilized over 20 years of experience and posting them here on this thread.

    PLEASE NOTE: You will not find miracle cures, aftermarket parts or anything else here. I believe that the most reliable way to repair this system is to understand how it works, why you see messages you do and common sense diagnostics to repair it.

    I have repaired over 8000 vehicles by using these specific processes and I believe them to be the most reliable in terms of accuracy of inspection, testing and implementing a repair. I utilize a lot of GM service information as far as wiring diagrams, voltage testing and description/operation of the vehicle systems.

    These steps will be laid out in detail over the next month. These steps are EXACTLY how I do my service work in my dealership, there is NO difference.

    So, keep your heads up, mind open and enjoy this layout to assist YOU in diagnosing your vehicle for maximum reliability. And if you have specific questions, please PM me for further information.

    Allthebest, Paul
    GM World Class Certified Service Technician.
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  2. #2


    Step 1: Battery condition and voltage checks

    The single biggest issue I have experienced with column lock issues is correct battery strength and voltage. This means a strong battery with clean battery cables, correct battery terminal bolts and those battery terminals correctly torqued to specifications.

    97-2003 require battery bolts be replaced everytime the battery is replaced. The reason why is quite simple, torque and oxidation. These bolts have a special conductive coating which assists in correct energy transfer from battery to terminals. The side terminal battery bolt GM part number is 19115561. Side terminal battery bolts are torqued to 11 ft lbs or 132 in lbs. And the key part to all of this is the CONDITION of the actual terminals, they must be CLEAN and free of any corrosion. If you remove the battery bolt from the terminal, the boot slides right off the top so you can correctly visually inspect the terminal to assure it is clean.

    Until 2001, the battery specification was a 78H battery which has a high reserve capacity. 2001, ZO6 was introduced and also the 75P AGM or absorbent glass mat technology. However, this battery was ONLY FOR ZO6. Coupe and convertible were still equipped with 78H classification. In 2004, the battery design changed for ALL models and they went to the 86 class. There is a lot of confusion in the parts catalog about the battery for certain models. Even GM dealerships can mistake the information. There IS NO CLARIFICATION for ZO6.

    The 75P battery is no longer produced and most dealerships do NOT know the classification difference and simply install a 75 conventional lead acid battery which does not have the strength to do all the work required of it on 97-03 models. ACDelco is now producing a 78 AGM battery and I do not have the GM part number as of this writing. This part number is what I use on the ZO6 2001- 2003. 2004, as noted above all 2004 models use the 86 class battery. In this year, I will always use ACDelco 86PS/ GM part number 88865255, due to better reserve capacity of 110 RC than the gold series of 95 RC.

    I ALWAYS install a 88865789 / ACDelco 78PSHR, Profession Silver High Reserve in coupe and convertible to 2003. This has a 140 reserve capacity to reduce tendency to drain the battery to a point where the BCM loses its feedback signal from the steering column lock actuator. 10.4 volts has been the threshold WHEN STARTING that I have noticed this failure occurs IF the electrical system is compromised.

    There is always the question, "Why cant I install an AGM battery in my coupe/convertible?" The reason is complex. The charging system programming, which is within the engine control module, is DIFFERENT between the coupe/convertible lead acid calibration and the 2001-2003 ZO6 AGM calibration. This difference can create shortened battery life if the correct battery is not used.

    THIS IS ALWAYS THE FIRST STARTING POINT TO ACCURATE COLUMN LOCK DIAGNOSIS, if you miss these simple first steps, all the other diagnosis you can do will not be accurate.
    GM World Class Certified Service Technician.
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