This is ESPECIALLY important to those of you who have installed a "LOCKOUT" switch that emulates the non-existent "HOOD IS CLOSED" switch to prevent a successful Remote Vehicle Start (RVS) sequence to start the engine if the hood is open in order to prevent some poor fool from having his extremities exposed to suddenly moving parts. You may be enjoying a false sense of safety.

I have just installed a tilt switch under the hood of my 08 LS former Enterprise fleet HHR to prevent UMM (Unintentional Mechanic Mangling). While checking the operation of this "automatic" RVS Lockout Switch, I think I uncovered a potential **DANGER** in this DIY RVS upgrade, and possibly a logic flaw in the BCM firmware.

After reading the HOWTO process for activating the RVS feature, I became concerned about the potential for UMM tragedies. While adding a toggle switch to the "HOOD IS CLOSED" input line to the BCM, as suggested on the RVS HOWTO forum, would, everybody assumed "lockout" the RVS sequence, I was a bit unsatisfied with the need for knowledge - intervention - activation of the switch in order to prevent UMMs. I decided that either a tilt switch or pin switch that would ALWAYS sense a "HOOD IS OPEN" condition was a safer approach.

With a tilt switch installed (more on that HOWTO in another post when I get it all finished) and the hood closed, I can successfully start and stop the engine with the fob two (2) times before having to do the manual start operation using the ignition key, per the owner's manual. So far so good.

If the hood is raised and the tilt switch is activated (ie in LOCKEDOUT state) BEFORE the ignition is turned off before executing any RVS requests, no RVS sequences are honored by the BCM program. So far so good.

HOWSOMEVER, if the hood latch is released after turning off the ignition and prior to exiting the vehicle with the hood only ajar, (which is how I for one usually do things), then after the hood has been raised, if an RVS is requested, THE ENGINE WILL START, RUN FOR A COUPLE OF SECONDS, THEN SHUT DOWN, but not until the UMM has already occurred.

I don't know if the "HOOD IS AJAR" switch would prevent this or not, but since the HOWTO doesn't address this issue, neither can I. Some time spent with the troubleshooting flow charts in the Shop Manual may shed some light on this issue.

I think the bottom line is that (without understanding the function of the HOOD IS AJAR switch more thoroughly), unless the "HOOD IS OPEN" switch (be it toggle, tilt or pin, is in the LOCKED OUT state PRIOR to the initial ignition turn off, the possibility exists for the RVS to be successful long enough to cause UMM.

Any of you who have activated the RVS feature and have installed a toggle lockout switch please check this out and report back here. Those of you who haven't installed ANY form of lockout should SERIOUSLY consider doing so. An unintentoinal RVS sequence of ANY duration (no matter HOW unlikely) is a bit like an accidental gun discharge (also no matter HOW unlikely) - either one is pretty damn hard to undo it once it has occurred and the damage is done.

 

UPDATE:

Looked thru the Shop Manual, no luck on more details. Tried experimenting and it looks like the HOOD IS AJAR switch would be CLOSED for the AJAR state and OPEN for the LATCHED state.

The HOOD IS OPEN switch works just opposite - it is OPEN for the OPEN/RAISED state and CLOSED for the CLOSED/LOWERED state.

This translates to adding two switches to the RVS system.

The Normally Closed (when the plunger is in the "up" position) switch will connect to the HOOD IS CLOSED input of the BCM (pin C1-3).

The Normally Open (when the plunger is in the "up" position) switch will connect to the HOOD IS AJAR input of the BCM (pin C1-4).

I'm giving up in the tilt switch concept and will try to buy a coupe of pin switches at a local alarm shop, assuming they carry both types. If they don't, I'll have to order a pair off the web.

BTW, the HOOD IS AJAR switch is also monitored by the HHR's security system. The first time I manually grounded that BCM input, it triggered the alarm.

Stay tuned ...........

 

wow!

 

Don’t know how much of what you have said above is theory verses actual, but I believe this danger issue was covered within post #3 of:
https://www.chevyhhr.net/forums/how-tutorial-library-21/how-add-gm-remote-start-without-option-ap3-28551/

 

SNO-WHITE

(1) Pardon me for wasting your time, but at minimum, the false sense of security in those members who put a switch in the connection at BCM C1-pin 3 could cause someone SERIOUS damage down the road - even after they have passed the HHR onto some unsuspecting person. If (no matter how unlikely it is) an Unintended RVS takes place, and injures just ONE person, who mos likely will not even be a member of this forum, but an innocent mechanic, the resulting personal suffering and legal consequences seem to be beyond your ability to grasp.

(2) NONE of my comments are theory - it is ALL based on what I have found by investigation and experimentation on my own HHR.

()3 Thx for the insult.

 

socalHHRguy - I do not think that Sno White intended to insult you - if so, the seven dwarfs put him (or her) up to it!
Actually, the thread Sno White refers to was posted almost a year before you even became a member of the forum.

I recently posted what I thought was a timely warning about thieves with code scanners that capture the signal from key fobs when people use them to lock their doors in mall parking lots, then program a key fob with the captured code and rob you blind when you are away from your vehicle.
Instead of a "thanks for the tip", what I got was a message that car manufacturers have been using rolling codes for years now - so that little trick is useless to thieves.
I was embarrassed, but not insulted. And I have been an electronics technician for 25 years!

 

socalHHRguy,

Oh, I’ve wasted plenty of time on this modification, especially considering I have a 2009 with the Remote Start straight from the factory and this has done nothing for me personally. Sorry to offend you.

Of Course, when you pass off the vehicle to another this and all other modifications should be disclosed to the recipient. I’ve even written my modifications(RPOs) on the glove box sticker. I would bet this specific modification would be a selling point of the vehicle and would clearly be demonstrated to a new owner. But, then again a vehicle could pass to another through death or another occurrence where there is no communications between owners. If not wanted for whatever reason by the new owner, I cannot think of an easier modification to remove.

Purchasing the proper OEM hood closed switch and the associated harness, as discussed in another thread would of course be the best and safest thing to do. Not many of us DIYers are going to go to that expense and thus we accept the ever-so-slight danger. For that discussion see:
https://www.chevyhhr.net/forums/general-hhr-4/hood-switch-testing-need-help-27502/

As for the miniscule chance of “inadvertent” activation of the Remote Start feature I personally regard it as just that – miniscule. “Intentional” activation is a much more likely occurrence and is what others and I have previously warned about. This was pointed out in at least three posts within:
https://www.chevyhhr.net/forums/showthread.php?t=28551
See post 3, 78 and is alluded to in post 65.

If you want to know more about how I feel about this overly safety cautious society see:
https://www.chevyhhr.net/forums/general-hhr-4/carrying-fuel-hhr-27563/
You should get a good chuckle.

Now down to business:
I did not find your original post to be clear, so I am still not sure if the switch in the grounding of BCM Pin #3 of Connector #1 is your concern OR the permanent grounding of Pin #3. Since I do not have a 2008 or prior vehicle I cannot experiment to your degree. Plus, I believe it was discovered that the 2008 & 2009 hood switches are different. Those pictures/schematics in ChevyMgr’s posts have been lost. As he has been.

How I understand the extra switch, from those who wanted to provide an extra bit of control or safety, is to temporarily deactivate this modification’s implementation. I presume for those times the vehicle is in for service. Are you saying that this extra switch does not work?

Thanks for pointing out once again the danger for anybody working in the engine compartment.

 

UPDATE:
After spending several hours on the phone and web yesterday, it appears that the "normal" pin switch used in the industry is normally CLOSED. When the plunger is up, the circuit is completed. That's the way dome light switches work. Any switches that work oppositely seem to be buried into complete alarm systems and can only be ordered by installers.

I did find some "door jamb" switches at Autozone that might have three terminals indicating the ability to perform either way. I will check them out in the next day or two.

BTW, re-visiting my notes, I think I got the switch types reversed. The HHR Service Manual is inconsistent in its use of the two terms. Sometimes they use switch status (ie open or closed) and physical parameter (ie hood ajar vs hood latched and hood open vs hood closed) in a kind d of sloppy manner, making it confusing to determine exactly what their original design was.

However, ALL THAT ASIDE, the fact that the HOOD IS AJAR switch DOES play some part in the RVS system operation is irrefutable, according to several areas of the Service Manual.

To SNO-WHITE, regarding your query: "Are you saying that this extra switch does not work?" The answer is YES, KINDA. It appears from my experimentation that if the RVS function is not locked out PRIOR TO shutting off the ignition, it will NOT prevent a "short cycle" engine start from occurring.

I found this out specifically using the following steps:
(1) Engine running normally.
(2) Engine stopped, key removed.
(3) Hood release pulled to "pop the hood" - hood is now in the "AJAR" but "CLOSED" PHYSICAL state, and with my tilt switch installed, the BCM sees "HOOD CLOSED" (ie BCM C1-Pin3 is GROUNDED to chassis) and "HOOD NOT AJAR" due to lack of any switch on that BCM input. That's the same thing that would be seen in a hardwired to ground mod or a mod with "the extra switch" set in the "HOOD CLOSED" position.
(4) Exited vehicle and executed an RVS sequence. Engine starts, and runs even though it should not because physically, the hood is AJAR/NOT LATCHED. That's because the BCM sees it as "HOOD NOT AJAR" due to lack of any switch on that BCM input. Not a desirable situation, but not particularly dangerous either.

Shut everything back down, re-latch the hood go back to step (1)
(1) same
(2) same
(3) same
(4) Exit the vehicle and raise the hood to the fully opened position. My tilt switch is now telling the BCM that the HOOD IS OPEN (similar to flipping that "extra switch" you mentioned). Keep in mind that the BCM still thinks HOOD NOT AJAR due to no switch on BCM C1-Pin4.
(5) Executed an RVS sequence. Engine starts, and runs for a few seconds, even though it should not start at all, because physically, the hood is BOTH ajar AND open. That's because the BCM doesn't see "HOOD AJAR" due to lack of any switch on that BCM input. This is the dangerous scenario that concerns me and that I for one wish to prevent.

As noted earlier, I used some clips leads to simulate the action of the HOOD AJAR switch. As also noted, in addition to being an integral part of the RVS system, it is also monitored by the security system. The first time I grounded BCM C1-Pin4, the alarm went off. When I did it correctly, it did lockout the short cycle RVS when the hood was "popped" but not raised all the way and also prevented it at step 5 above.

It's the false sense of security that "the extra switch" provides to people that really worries me. It will only provide protection under certain circumstances. And yes, the RVS can really be locked out manually via the DIC if that step is remembered.

BTW, I too am not fond of the litigious nature of our society. However, injury and liability are two different things and frivolous law suits/tort lawyers are different yet again. I have little sympathy for someone burned by careless handling of the hot coffee they just purchased. Hundreds of people injured and/or killed because some lazy dudes didn't follow proper procedure for replacing an engine on a DC10 is all together another case.

The third or fourth owner of an HHR with an improperly added RVS feature could become a victim through no fault of their own.

Lastly, I'm not some Quality Control freak/genius - I STUMBLED on to this flaw totally by ACCIDENT and quite frankly it scared the s*** out of me, and THAT's why I'm trying to shine some light on the issue. In my first post on the subject, I asked for feedback for other members on their experiences on the issue, but haven't heard anything yet

I'm new to the forum after putting >75K miles in one year on my HHR delivering blood for the Red Cross here in SoCal. It can be pretty brutal getting in and out of a car a dozen times a day here in the summer. The RVS was a mod that REALLY got my attention. I got some good assistance on an oil related problem early on in my membership, but based on the responses to my first attempt at providing what I thought was helpful info, I guess I'll go back to just lurking.

---Some things you can do over, but some things, once done cannot EVER be undone, no matter HOW sorry you are after the fact.

 

I wish I would have never promoted this mod in any way. I never thought about one of you selling the modded vehicle to another person who does not know the mod was done and then them loosing a hand because the override feature for the hood being opened is NOT there.

I would suggest anyone selling their HHR with this mod to undue it before putting it up for sell.

 

AND this modification is by far one of the easiest to undo.