by chrome_eater » Sun Oct 09, 2016 5:27 pm
It has been 2 weeks now and I have had zero issues since installing the newrockies module. Here is what I have learned about the H3 security system:
H3 security system overview. This is my understanding of how the security system works and what the different parts of it are and what to look at if it fails. I would not claim to be an expert on this, this is just what I have been able to piece together from all the info I could find out there, I could be wrong about any number of things and any corrections or additions are welcome.
GM has used the same security model for decades. It has many different names and versions – VATS, Passlock, Passlock II, Passkey, etc... but they all work in basically the same way.
Part one: the ignition – there is a resistor, or a chip, or a radio transmitter in either the key itself or the ignition. In the H3 the key is just a plain key – there is no chip, resistor, or anything else in the key. *** Apparently export H3's (non-US sold) may have a chipped key (resistor in the key) - *** thanks Mark. The ignition sends signals to the TDM.
Part two: The Theft Deterrent Module (has been called multiple different names over the years – I will call it the TDM) – reads the signals from the ignition and if that signal matches what it is expecting then the TDM sends a signal to the ECU saying – "OK". In the H3 the TDM is not a separate piece, it is integrated into the BCM. Also in the H3, in addition to not sending the OK signal to the ECU if it does not like the signals coming from the ignition, the BCM will disable the starter.
Part three: the ECU (engine management computer) looks at the signal coming from the TDM (in the H3 that is the BCM) and if it does not get the OK signal it shuts off the fuel injectors.
Any of these three parts can fail, but the most likely one is the ignition because that has moving parts and due to the design of the ignition and how it is connected. Next most likely is the BCM – this is the real "brains" of the security system in the H3 – it is doing all the figuring out if it likes the signals coming from the ignition and enabling or disabling the starter and sending the OK signal or not to the ECU. Least likely to fail is the ECU.
What to look at in the H3 if you have security system problems by symptom:
The cheapest (free) thing to try but may not work and make things worse – do a passlock relearn – see below for how and why/why not.
Note: there are Passlock II “bypass” kits out there for about $40 – basically this is just a resistor in a box that you wire into the ignition. These MIGHT work depending on exactly what has gone wrong, but if you are the DIY type and are comfortable with cutting and splicing ignition wires, then I would just get a 7.5K ohm 1% resistor that costs about a penny and solder it in there and do the relearn and save the extra $39.99 + shipping (just me).
1) security light blinking and no crank on start – wait 10 minutes and it might start: (this is the problem I had) repair or replace the ignition or install newrockies module or remote starter? (see below) to bypass the ignition. If that does not fix it, replace the BCM.
2) H3 does crank, but does not start or dies shortly after starting. This might be a candidate for a ECU flash. The ECU can be flashed with a new config file to tell it to ignore the "OK" signal from the BCM and just always have the injectors on and never turn them off. Or replace the BCM or ignition.
Note: if you replace the ignition and/or the BCM you need to do a relearn, unless you just happen to get an ignition and BCM that match. I don't think you have to do a relearn if you replace the ECU, not sure though.
Some info out there says you can just flash the ECU to always have the injectors on and that will "fix" GM security system problems, but that won't work on the H3 if you have no crank – the BCM has disabled the starter and it does not matter if the injectors are always on if the starter is disabled.
Something that might work is this: flash the ECU to tell it to always enable the injectors and bypass the BCM starter disable – not sure exactly how to do that but it might be fairly simple – find the starter disable relay and modify it accordingly. If the injectors and the starter are the only things disabled by the security system then this seems like it should work, but I'm not sure those two things are the only things that get disabled so this might not work.
If I was getting a tune and flashing the ECU I would also turn off the injector disable so I would never have to worry about that part of the system, the security system will still work because the BCM will disable the starter. Perhaps that is why there are two disable mechanisms – the injectors and the starter – it might be fairly easy to pop the hood and bypass the starter disable, I don't know.
Unfortunately there is no easy way to know what exactly has gone wrong and what part to replace/repair/modify when you have security system problems. I would suspect the ignition first – that is the part that seems to fail most often and it makes sense that would be the case given the moving parts and design issues.
Passlock 30-Minute Learn Procedure
Turn ON the ignition, with the engine OFF.
Attempt to start the engine, then release the key to ON, vehicle will not start.
Observe the SECURITY telltale. After approximately 10 minutes, the telltale will turn OFF.
Turn OFF the ignition, and wait 5 seconds.
Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes. The vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.
Important: The vehicle learns the Passlock™ Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
Start the engine. The vehicle has now learned the Passlock Sensor Data Code and/or password.
With a scan tool, clear any DTCs if needed. History DTCs will self clear after 100 ignition cycles.
Remote starters – some people report fixing this problem by installing a remote start system. If the resistance of the ignition has changed to a new stable value and a relearn is done as a part of the remote starter install, that will "fix" it as long as the resistance value stays the same in the ignition. Also, I guess it is possible that the BCM just forgot the correct value and a relearn fixes it. I would be careful about doing a relearn if you have not fixed the problem first – two sides to this coin – it might fix it without replacing anything or you might relearn junk and it will never start again until whatever problem is fixed and a relearn is done again.
Any corrections or additions are welcome and I hope this helps people figure out what is going on when they have security system problems and hopefully how to fix it. I spent many hours trying to figure out how the H3 security system works and ended up going down a rabbit hole, hopefully this will save someone time and frustration.
Last edited by
chrome_eater on Wed Oct 26, 2016 11:32 am, edited 1 time in total.