05 Trialblazer security system Question

[MrGiggles]

This is my first 05 trailblazer it may be a bugger to work on but I like it and it's my first trailblazer.

On my Trailblazer to start the vehicle I have to click the unlock doors button on the remote then turn the key to start the vehicle is this normal for all Trailblazers?

 

[Blckshdw]

No, that's definitely not normal. Does your truck have an aftermarket alarm or anything added to it? What type of behavior does the truck have when you try to start it without pressing the unlock doors button?

 

[MrGiggles]

If you try to start it with out pressing the unlock remote button then turn the key nothing other than the dash lights dim out for a second like it will try to start but nothing happen starter does not even click.

When you turn it off to start it again you have to press the unlock button on the remote again to start it.

Weirdly I have been having issues with the trailblazer the alarm is original no modifications to the vehicle if this is not normal maybe the truck has a bad PCM been having weird codes popping up see this thread https://gmtnation.com/forums/threads/05-trailblazer-bad-pcm-question.20373/ and you will see what I mean almost every thing under the hood is new and engine rebuild around 100 miles running out of parts to change. Don't trust the vehicle until I debug it in town driving only.

Only new items I can change under the hood is the complete wiring harness, PCM, battery, AIR conditioner compressor and the mass air flow sensor meter on the hose between the air filter and throttle body. The intake map sensor is new the intake manifold is original I cleaned it out (de greaser and power washed it let it dry 3 days in the sun and replaced the hose on it made it like new has no cracks or leaks..

Look at my other post maybe I'm on the right track now knowing the press unlock button on the remote to start the trailblazer is not normal. Been working on this truck for a tear and love it but it's a bugger to work on gone to far to turn back now

My biggest worry changing the PCM is I now the security system will re sync with the key just left on for 30 minutes but finding a mechanic that can relearn the crankshaft position sensor to the new PCM in my area I know the chevy dealer will ask for my next child to do this.

unless there is a back boor procedure to program and relearn the crankshaft position sensor via turn key on or off pressing gas pedal down or some thing like that.


Your help is appreciated!

 

[Mooseman]

How's the battery? Have it checked lately? What about the ignition switch? It can also cause weird electrical gremlins.

 

[MrGiggles]

The ignition switch how would I check if it's bad as long as I press the unlock remote button it starts ok without hesitation. As far as the battery I had it tested at three auto parts stores. Orielys said it's ok just needed a charge, napa said it's ok and need a charge and autozone said the battery is bad and I needed to buy one now
I charged it over night the battery has not gave me any issues I may pull my wife's battery tomorrow and test drive it.

 

[Mooseman]

You could test the switch but if it's an intermittent issue, you'd be chasing ghosts. Because it's such a relatively cheap part and easy to replace, we just say to go ahead and replace it.

It's definitely not a security feature of the truck. Does the security light flash before or after trying to start it?

 

[MrGiggles]

I just put in a new ignition switch no change still have to click the remote unlock button to start the truck when you turn the key. And the other issues as the same. I guess it could be a bad PCM after all before the complete engine rebuild it had 196k on the truck and PCM is original. Hate to fork out the new PCM price

 

[Mooseman]

Does the security light flash before or after trying to start it?

Please answer my question.

 

[Blckshdw]

Spit balling here... What happens if you press the unlock button on the driver's door, at the same time as turning the key, instead of on the fob?

 

[MrGiggles]

never see the security light on unless I take the keys out close the doors and lock the truck with the remote it stays on briefly.

The only other time I see the security light is if the vehicle is running and I plug in my scanner and scan for codes then it will come on and stay on until I restart the truck after taking the key out.

 

[MrGiggles]

I checked this:

"Spit balling here... What happens if you press the unlock button on the driver's door, at the same time as turning the key, instead of on the fob? "

VERY FREAKY NEVER SEEN THIS BEFORE!

1.) I put the key in and tried to start the trailblazer with just the key nothing happened.
2.) I press the unlock button on the drivers door the starter turned but did not start the truck.
3.) Turned the key to start and it started.

Also

With your suggestion found out I can press the drivers door unlock button then turn the key and it will start.

I'm really confused on this! WOW!

 

[Blckshdw]

I was thinking, if you have the truck locked, you're already using the fob to turn of the security and unlock everything, before you even try to start the truck. So the security system shouldn't be in play. The unlock function is handled in the BCM, not the PCM, so your problem may lie under the back seat, and not under the hood (for this issue) Checking some of the schematics confirmed, which is what gave me that idea.

Ideally, you could swap BCMs with another truck, let the security relearn process run, and then test it to see if you still had the same behavior to know if a replacement would fix the issue.

 

[Mooseman]

I'm thinking maybe, just maybe, the driver door module is flaky. Try unplugging it and see if it starts. Maybe the Databus is being so screwed up that it prevents it from starting.

Are there any codes? Not just P codes, but U codes? I'm wondering if the DDM is doing something.

Ideally, you could swap BCMs with another truck, let the security relearn process run, and then test it to see if you still had the same behavior to know if a replacement would fix the issue.

I don't think you can just swap a BCM like that. The VIN has to be programmed into it as well as the VATS. Might work.

 

[Blckshdw]

I don't think you can just swap a BCM like that. The VIN has to be programmed into it as well as the VATS. Might work.

You can... A former forum member who owned the bagged Envoy before Ken, used to live near me. He had a weird problem with his cluster, so we swapped BCMs to see if that was the case. After the 30 minute relearn process, both of our trucks started and drove with the other's module. Had to do the relearn again when swapping back, of course.

 

[TJBaker57]

So I am curious...is the vehicle locked up when parked? Specifically, do you have to unlock it to get in to start it, or try to start it? If it is locked when parked how do you open it to gain access? FOB or key?

If it is unlocked, have you tried pressing the fob unlock or drivers door unlock button first before ever trying to start it?

press the unlock button on the drivers door the starter turned

Am I to understand that the starter engaged when you pressed the door unlock button WITHOUT the
key in the crank position??

never see the security light on unless

FWIW, when I turn my key to the run position the SECURITY light comes on with the 'check gages', 'service 4wd', 'change engine oil', and 'service engine soon' lights as well. Only the service engine soon light remains on until the engine is started.

Edit: Another query...Is the key an original or a copy?

 

[MrGiggles]

I'm thinking maybe, just maybe, the driver door module is flaky. Try unplugging it and see if it starts. Maybe the Databus is being so screwed up that it prevents it from starting.

Are there any codes? Not just P codes, but U codes? I'm wondering if the DDM is doing something.



I don't think you can just swap a BCM like that. The VIN has to be programmed into it as well as the VATS. Might work.

No Codes

 

[MrGiggles]

So I am curious...is the vehicle locked up when parked? Specifically, do you have to unlock it to get in to start it, or try to start it? If it is locked when parked how do you open it to gain access? FOB or key?

If it is unlocked, have you tried pressing the fob unlock or drivers door unlock button first before ever trying to start it?


Am I to understand that the starter engaged when you pressed the door unlock button WITHOUT the
key in the crank position??


FWIW, when I turn my key to the run position the SECURITY light comes on with the 'check gages', 'service 4wd', 'change engine oil', and 'service engine soon' lights as well. Only the service engine soon light remains on until the engine is started.

Edit: Another query...Is the key an original or a copy?

I had the key in run/driving position pressed the unlock button and the starter turned the motor over freaked me out so I instantly released it this only happens if I try to start with out pressing the unlock door button or the unlock key button like this.

1.) try to start nothing
2.) press door unlock button starter will turn over the engine let of button because no start happens
3.) After this the engine will start with the key.

or

1.) press fob unlock button
2.) engine will start with key

or

1.) press the unlock button on door when I left the trailblazer unlocked for a while with out pressing any buttons for the next 5 minutes
2.) Turn key and starts

or

1.) Do not press unlock on fob or door unlock not start.

and

Trailblazer is locked via key fob:
1.) Unlock doors using key fob
2.) Get in truck turn key to start and not start
3.) press key fob unlock or door unlock button
4.) turn key to start and truck starts

Tomorrow I will check the rider door unlock button and back door unlock buttons see what happens.

 

[MrGiggles]

So I am curious...is the vehicle locked up when parked? Specifically, do you have to unlock it to get in to start it, or try to start it? If it is locked when parked how do you open it to gain access? FOB or key?

If it is unlocked, have you tried pressing the fob unlock or drivers door unlock button first before ever trying to start it?


Am I to understand that the starter engaged when you pressed the door unlock button WITHOUT the
key in the crank position??


FWIW, when I turn my key to the run position the SECURITY light comes on with the 'check gages', 'service 4wd', 'change engine oil', and 'service engine soon' lights as well. Only the service engine soon light remains on until the engine is started.

Edit: Another query...Is the key an original or a copy?

I only see the security light flash on then off when starting

And noticed when I lock the trailblazer using key fob by pressing the key fob lock button two times and the truck honks the light will stay on when I return to the truck and the dome lights are off the security light on the dash is off.

 

[mrrsm]

Without knowing which Brand-Model your Keyless Remote-Entry Starter System employs... if the problem is NOT with the Ignition Switch acting Hay-Wire as suggested by @Mooseman... Consider the information shown in the Link Below on a similar system Wiring Diagram which specifies that an ADDITIONAL COMPONENT is needed in order to bypass the PASS-LOCK Security Issues. It is called:

The 791 Bypass Module

If your After-Market System demands the use of this as a similar additional Module to work in order to Activate the Remote Starter feature... perhaps THAT particular AM Module has gone "T*Ts Up" within your Wireless Add On Remote Starter "BOX":

Please observe the "NOTE #1" at the Bottom of the Wiring Matrix Columns here:

2002-2007 Chevrolet Trailblazer Vehicle Wiring Chart and Diagram

Commando Car Alarms offers free wiring diagrams for your 2002-2007 Chevrolet Trailblazer. Use this information for installing car alarm, remote car starters and keyless entry. View our complete listing of wiring diagrams for your Chevrolet Trailblazer.

www.commandocaralarms.com

 

[MrGiggles]

Wondering does the BCM also run the cruise control all the fuses are good in the trailblazer but the cruise control does not work and the dash cruise on light does not show up. I was told this could be the brake switch if the brake lights get stuck on but the brakes lights work normal. May be another indicator of bad BCM not sure.

 

[mrrsm]

This Topic of "Questionable Modules" on the Class 2 Network where ONE BAD APPLE (Module) can make the entire network go sideways has been nicely investigated in this Linked Video:

Post # 20...

Additional Tech 2 & VXDIAG Nano Resources

EDIT: On November 11th, 2019, :I created a TOC (Table of Contents) of the Video Files shown consecutively in the following Threads that should help to speed the identification of Specific On Topic Videos vs. having to Read and Watch each one in sequence to locate what the Viewers need. The...

gmtnation.com

At the very least... it will explain how there are TWO Single Wire Network "Combs" that connect ALL of the Modules on a Single, Collective Connection Point (One under the DASH and One under the Passenger Rear Seat) that will allow you to "Take the Network DOWN" and then bring up One Module at a Time to discover any culprits that have been making your "Dash Lights" go Crazy.

Even if you do NOT possess a "GYMKO" Tech 2 Scan Tool or a Higher End Flavor of one... This Video will still prove very enlightening. Please Note that there does NOT seem to be any reference made to a Separate Module controlling the Cruise Control (which really should fall under the Engine Controls being handled via the PCM) nor relating IT to the BCM on "The List of 15 Modules" shown on the Tech 2 Screen during this Video.

 

[MrGiggles]

I found a scanner that maybe my brother in law will pay 50% for so we can both use it.

What do you think about the Autel MaxiCOM MK808 OBD2 Scanner Diagnostic Scan

My understanding it can rest/Relearn the camshaft position sensor, PCM, BCM and code car remotes / key plus a lot more rest / relearn features upto 8 different reset features and normal scan features.

Do you think it's work the investment since we both work on our own vehicles?

I have a 05 trailblazer and wife has a 2013 nissan juke. He has a 2016 chevy truck, ford explorer year ? and two ford trucks for his self employed business plus his son has a dodge neon.

Didn't want to buy it unless everyone thinks its worth the money and can save trips to deal or local mechanics just to program something we can do. Also currently looks like it may come in handy on my trailblazer and his truck he just had to order a throttle body position sensor repair kit and will have to do a relearn and my wife car needs a new remote coded since she washed her fob and took mine last year.

 

[TJBaker57]

No Codes

As I understand it, a failure or fault condition of the security system will NOT enable the check engine light but WILL set a DTC code that may not be read by all scanners as it is a Body Control module code. It will begin with a 'B' rather than a 'P' or 'C' or 'U'. Have you ever seen a 'B' code in your scanner? (I think you said you had a cheesy old scanner?)

 

[Mooseman]

I think it's worth the money. The only thing it probably can't do is program or calibrate modules (i.e. passthrough). If splitting the cost, it would be about the same as a Tech 2 but can use it for any vehicle manufacturer.

Has the truck always done this or did it start all of a sudden? If it always did this, I'm now thinking that this may be some sort of aftermarket anti-theft device. Have you looked under the dash for something that looks added on? It just sounds improbable that even with a fault of some kind that the engine could be started using the door switch. The door module would have to basically mimic the crank request signal that is normally sent by the ignition switch directly to the PCM.

This is just too weird.

 

[MrGiggles]

my scanner is a cheesy cheap elm327 clone but there are no codes given.

 

[TJBaker57]

And noticed when I lock the trailblazer using key fob by pressing the key fob lock button two times and the truck honks the light will stay on when I return to the truck and the dome lights are off the security light on the dash is off

All the descriptions of security behaviour sound pretty normal to me.

Has there been any flaky behaviour using key fob to unlock the doors? Do you have a second keyfob? A second key perhaps? My understanding is the liftgate module does the business of receiving the keyfob signals and opening the doors by communicating with the door module(s) through the data bus.

Operations are scattered about the various modules. The PCM starts the engine but not before getting the OK from the BCM. The BCM gets input from the ignition cylinder lock sensor (Passlock in my 2002) that a proper key has been used and the lock cylinder has been rotated properly. Additionally I have read about a 'password' is sent from the BCM to the PCM after the engine starts essentially telling the PCM that all is OK. Lacking this 'password' being delivered within a predermined time frame the PCM will disable the fuel delivery and the engine dies. This is not your issue but it sheds a light on some of the complexities of the simple act of starting the vehicle. Yours is sounding more and more like a communication issue perhaps, or a door module, BCM, Ignition Cylinder sensor, or even LiftGate module

 

[mrrsm]

...and for the TIS2WEB SPS Programming... Autel has THIS Item (Autel "J"-Box J-2534) or one LIKE it... to re-program the GM PCMs and Assorted NEW Modules:

 

[TJBaker57]

my scanner is a cheesy cheap elm327 clone but there are no codes given.

Is it bluetooth? Is this used with an android app? I ask this because while the Torque App will scan modules for current or pending codes, an older app, Car Gauge Pro, can scan for old (cleared) codes and more. Sometimes this yields interesting history of the vehicle perhaps from before one acquired the truck.

 

[TJBaker57]

Wondering does the BCM also run the cruise control all the fuses are good in the trailblazer but the cruise control does not work and the dash cruise on light does not show up. I was told this could be the brake switch if the brake lights get stuck on but the brakes lights work normal. May be another indicator of bad BCM not sure.

I believe the BCM is NOT involved with Cruise Control. As for the brake switch, there are 3 separate circuits in the one physical brake switch. The circuit that does the stop lights is not the circuit that enables the Cruise Control so the stop lights are not an indication that the cruise control 'brake switch' is OK.

 

[MrGiggles]

I believe the BCM is NOT involved with Cruise Control. As for the brake switch, there are 3 separate circuits in the one physical brake switch. The circuit that does the stop lights is not the circuit that enables the Cruise Control so the stop lights are not an indication that the cruise control 'brake switch' is OK.

OK so it maybe worth the $12 part to change it out now that I know it has three curcits in the switch.. The engine is rebuilt but the truck has 196k on the truck with 90 miles on the engine and that is a lot of brake pedal usage. Still cheaper than having a car payment I like zero payments

 

[MrGiggles]

Is it bluetooth? Is this used with an android app? I ask this because while the Torque App will scan modules for current or pending codes, an older app, Car Gauge Pro, can scan for old (cleared) codes and more. Sometimes this yields interesting history of the vehicle perhaps from before one acquired the truck.

Yes its android I currently us the app CarBit I will download Car Gauge Pro but get a warning the app is built for older version I will give the lite version a try first.

 

[TJBaker57]

OK so it maybe worth the $12 part to change it out now that I know it has three curcits in the switch.. The engine is rebuilt but the truck has 196k on the truck with 90 miles on the engine and that is a lot of brake pedal usage. Still cheaper than having a car payment I like zero payments

Have a look here...

SOLVED! - Won't go into gear

Sometimes, infrequently, my shifter refuses to budge. It only happens every two or three weeks and then is normal. I start the TB, try to move the shifter to D or R, and it doesn't move. I have to jiggle it, pull harder, say a little prayer and then it will move. I checked the brake light...

gmtnation.com

The switch can be a pain to get off.

 

[TJBaker57]

Yes its android I currently us the app CarBit I will download Car Gauge Pro but get a warning the app is built for older version I will give the lite version a try first.

Car Gauge pro can take some getting used to. But once you figure it out it can get things other apps do not.

 

[MrGiggles]

Have a look here...

SOLVED! - Won't go into gear

Sometimes, infrequently, my shifter refuses to budge. It only happens every two or three weeks and then is normal. I start the TB, try to move the shifter to D or R, and it doesn't move. I have to jiggle it, pull harder, say a little prayer and then it will move. I checked the brake light...

gmtnation.com

The switch can be a pain to get off.

That post helps a lot and yes I would have learned some new four letter words taking that clip off glad you directed to that post. Also when I press the break I hear no click sound so I'm thinking cruise control circuit in the switch may be the cruise control issue worth like you said. I'm ordering the part now. Thank you

 

[TJBaker57]

OK so it maybe worth the $12 part to change it out now that I know it has three curcits in the switch.. The engine is rebuilt but the truck has 196k on the truck with 90 miles on the engine and that is a lot of brake pedal usage. Still cheaper than having a car payment I like zero payments

To avoid thread drift, the Torque Pro app and these GMTN additional PIDs can help with your Cruise Control troubleshooting. You will be able to test the multi-function switches and verify brake switch operation right in the app.

More PIDs for Torque App

A short time ago I posted a new pid I discovered for the Fan Speed of a 4.2 in a 2002 Trailblazer. It was properly suggested by MRRSM that I repost that information here so here I am. It is possible that this is my first original post! I have been spending a great deal of time fiddling with...

gmtnation.com