If I changed my ignition housing do I have to change the key and lock cylender...2008 trailblazer 4.2
Ignition
- Thread starter Josh2008tb
- Start date
Not sure. And a related question would be, when replacing a lock housing, presumably including the passlock sensor, do they look up your VIN and get a matching passlock sensor or are you destined to do a security relearn?
We just got the lock cylender and housing and key from autopart store and didn't work so we put old one back in..
So here's the thing. If you change the part that has the small 3 wire sensor (passlock) in it you will almost certainly get a flashing security light (might sometimes be a solid security light) when the key is turned to CRANK. This is because that sensor has to be matched to the BCM. The BCM can 'learn' a different sensor by doing the "security relearn" procedure which takes a little more than a half hour and almost always requires a battery charger or booster to keep the battery from going too low while doing the half hour procedure.
I have a feeling that if the security relearn is not done and you keep fooling around turning the key on and off trying to start it you might get "locked out". I have no documented proof of this, just observations of troubles others have had.
Mooseman
Moderator
I'm not so sure about that. The 30 minute relearn is for the "handshake" between the BCM and PCM. If the key sensor is replaced or disturbed, that requires a Tech 2 to have the BCM pair up to it.
A couple months ago I posted a writeup here somewhere about the security relearn. In that writeup I replace my original BCM with a junkyard unit of the same year. The security relearn procedure was followed and the truck started and operated after the relearn.
I also recorded the enitire class 2 serial data throughout the relearn for examination.
Exploring the security relearn
So yesterday I took a junkyard P10 PCM from a 2002 built in 06/01, the same year truck as my 4. 2, a 2002 built in 10/01 and installed it and did the security relearn. First time doing this for me. I had already interrogated this junkyard PCM on the kitchen table, connecting C1-20 and C1-21...
gmtnation.com
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Mooseman
Moderator
Hmmm. All the literature I've read said that the relearn was for the sharing of the code from the BCM to the PCM. Maybe the key sensors all have the same resistance? In any case, sure seems to work.
I might do a writeup of the Passlock sensor(s). I have collected 3 from junkyard trucks, opened them up, traced the circuits and know now how they work, and identified the 2 pertinent resistors, one for tamper, one for operation. All have different resistances for iperation but matching tamper resistors.
On my bench setup of a PCM, BCM, Cluster, and ignition switch (not housing) I can imitate the passlock with a potentiometer set to the resistance measured in the matching passlock sensor.
On my bench setup of a PCM, BCM, Cluster, and ignition switch (not housing) I can imitate the passlock with a potentiometer set to the resistance measured in the matching passlock sensor.
This article covers the entire spectrum of the various GM ATD Designs.
(It looks like its @Mooseman FTW on this one...)
GM PassKey and PassLock overview
How the GM PassKey and PassLock anti-theft systems work.
ricksfreeautorepairadvice.com
(It looks like its @Mooseman FTW on this one...)
No offense meant, Tom... Just trying to Dial in on the OP's concerns and what he might be able to do to avoid any entanglements if he goes ahead and makes changes with his Steering Column and Lock Work Hardware... That's all.
Based upon the information in the lower paragraphs on the above mentioned Link... the Major Components missing from your Excellent Bench Top Testing Equipment set up may alter the outcome of making this work are the Steering Column Housing (containing the Hall Effect Sensor) , the Key-Lock Cylinder (containing the concealed Tiny Low Power Magnet) and the Plain Ignition Key, which if installed as is the case inside of the vehicle... might automatically prompt the need to use a Tech 2 and follow through having to employ the Re-Set Commands for convincing the PCM that the SUV is NOT being stolen.
Based upon the information in the lower paragraphs on the above mentioned Link... the Major Components missing from your Excellent Bench Top Testing Equipment set up may alter the outcome of making this work are the Steering Column Housing (containing the Hall Effect Sensor) , the Key-Lock Cylinder (containing the concealed Tiny Low Power Magnet) and the Plain Ignition Key, which if installed as is the case inside of the vehicle... might automatically prompt the need to use a Tech 2 and follow through having to employ the Re-Set Commands for convincing the PCM that the SUV is NOT being stolen.
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No offense taken! I must admit there are holes in my experiment. Certainly the BCM and Passlock were a mismatch and that was corrected with the relearn. But what of other components in the truck? Can a mismatched VIN from PCM vs BCM and even perhaps the radio cause security issues? I want to design and do a test where I alter ONLY the Passlock sensor and run a relearn to confirm my thoughts about this matter. I intend to pursue this in my security relearn thread.
Now back to the OPs issue. Looking back over all the related posts josh has made there has been a lot of replacement wiring and alterations to original wiring such that it is difficult if not impossible to say what the current status is.
Fair Enough, Brother... That linked read stressed the Special Pass-Lock Design of the Housing itself as containing a Hall Effect Sensor and a Small Magnet in the Tumbler that WILL get ripped out with the Key Lock Cylinder if it gets yanked out by any Car Thief.
It seems like without having those other physical components present and designed right into your other Bench Top Test Equipment ... side-stepping all of that Steering Column Hardware might miss the part that the PCM expects to interact with in order to start the SUV For REAL and keep it running.
I too have had experience with Designing and Building functional GM P-10 PCM Bench Top Harness Equipment for programming the PCM . And I too managed to side-step any limited access to the PCM involving any possible security issues... just by using a Toggle Switch.
I figured out that having the PCM AND the BCM knitted together into my Desktop Harness Set Up turned out NOT to be necessary. But the OP's problem WILL have to be sorted out "in situ" ...and so @Mooseman's recollections of having to use a Tech 2 to perform the Security Re-Learn and set the OP's World Right again by doing so... weighs in pretty strong with being able to solve this issue.
It seems like without having those other physical components present and designed right into your other Bench Top Test Equipment ... side-stepping all of that Steering Column Hardware might miss the part that the PCM expects to interact with in order to start the SUV For REAL and keep it running.
I too have had experience with Designing and Building functional GM P-10 PCM Bench Top Harness Equipment for programming the PCM . And I too managed to side-step any limited access to the PCM involving any possible security issues... just by using a Toggle Switch.
I figured out that having the PCM AND the BCM knitted together into my Desktop Harness Set Up turned out NOT to be necessary. But the OP's problem WILL have to be sorted out "in situ" ...and so @Mooseman's recollections of having to use a Tech 2 to perform the Security Re-Learn and set the OP's World Right again by doing so... weighs in pretty strong with being able to solve this issue.
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...or access to a High End Scanner courtesy a Reputable Local Auto Repair Shop... (with an Autel, Snap-On or other High Quality and equally capable Bi-Directional Scanner, Etc...) Try calling around to some Local Auto Repair Shops (NOT Dealerships) and explain your dilemma to find out what they would Charge for doing this Key-Lock Tumbler-Ignition Security Update. If your vehicle is not drive-able. find out if they would 'Throw in a Tow' for not too much more Money... This is where paying to be a AAA Member pays off, too... (I've been a Member since the early 1970s and in nearly 50 years... I've used those services more times than I can count).
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Thankyou I have a buddy with one I'll see if he will do it for me...I must note that everything is back in it's original way when I bought it
Cool Beenz... In the mean time... Find out if the Scanner he is using is a Tech 2 and if so... Download and Email him THIS amazing and useful Tech 2 Resource PDF. He'll certainly appreciate having it and perhaps it will coax him to help get you back on the road ASAP: