Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 20 of 45 Posts

·
Registered
2003 chevy trailblazer_ls
Joined
·
25 Posts
Discussion Starter · #1 ·
Just got a used pcm off from eBay. The vendor "flashed" my vin number into the pcm, supposively as calibrated software claiming "ready to install." I bought this to use as my "spare stock unit." I'm preparing to send my current pcm on the truck to PCMForLess tuning. So I thought it was time to install the spare one before I mail it in because I need a running vehicle. Well, I put the spare one in and plugged it all together. I turn the key and nothing. The SECURITY light flashes at me when I attempt to crank it. Someone told me it needs the security relearn procedure. But how? Anyone with exact instructions? Thank you.
 

·
Registered
2004 chevy trailblazer_ls
Joined
·
319 Posts
THAT'S SIMPLE GO TO FORUM AND THEN CHOOSE SUPPORTING VENDORS A PICK PCMFORLESS THEY SHOULD BE A REALARM INSTRUCTIONS IN ON OF THEIR THREADS IF NOT FIRST THING TOMORROW MORNING I'LL WRITE IT UP FROM THERE INSTRUCTIONS THEY SEND WITH THE PCM.:m2:
 

·
Registered
2003 chevy trailblazer_lt
Joined
·
6,568 Posts
case relearn and security relearn are totally different.. lol.. but yea the link is what ya need to do.. but a case relarn would need to be done if the vendor who programed the PCM didnt do it already..
 

·
Registered
2003 chevy trailblazer_ls
Joined
·
25 Posts
Discussion Starter · #5 ·
Security Relearn Complete

Got it to start after doing about an hour worth of key on for 11 minutes and key off for 30 seconds. I'm not sure how EXACTLY it was suppose to work, but a friend told me to keep doing this "until it starts." After the 4th cycle, it did NOT start as I hoped for, but the truck decided to fire right up on the 6th cycle. I drove it for about 20 minutes in stop and go traffic. The SES light did not illuminate. Does that mean no CASE relearn required?
 

·
Registered
2003 chevy trailblazer_ls
Joined
·
25 Posts
Discussion Starter · #7 ·
Security Relearn Procedure

I got this GM security relearn procedure from a friend who is a ASE certified technician.

After you install the new pcm (make sure your pcm is indeed flashed specific to your vin) try to crank the truck by holding the key to the start position without letting go. It won't start and the security light will continue blinking while you hold the key to the start position. Release the key to the on/running position (do not turn off).

Wait 11 minutes (cannot be any less than 11 minutes) with the key left to the on/running position. The security light will remain on for the time being and will eventually turn off by itself.

While you wait, it would be wise to turn off all accessories and interior lights, dim the dashboard lights, and bypass the daytime running lamps (DRL) to avoid draining the battery since this is a ridiculously long process. To bypass the DRL, turn the headlamp switch counter clockwise to the farthest left setting and hold the switch to that position for 3 seconds and release. The DRL will be switched off, however it will come back on by default during each cycle, so yes it is a pain to do it again and again, but it ensures that your truck will have enough juice to start.

After the 11 minutes is up, switch the key to off position for 30 seconds (cannot be any less than 30 seconds).

Switch the key back to on/running position (do not attempt to start the truck just yet) and wait another 11 minutes.

Switch the key back to off position for 30 seconds.

Repeat this cycle four more times.

But on the final 6th cycle, after switching the key to off position for 30 seconds, switch the key to the on/running position for a split second so the security light can come on, then immediately crank the truck before all the chimes and instrument cluster icons go off. THIS IS THE ONLY POSSIBLE WAY I GOT THE TRUCK TO START.

Hope this helps.
 

·
Registered
2002 chevy trailblazer_ls
Joined
·
281 Posts
just throwing it in the air...would this work if my battery went dead and when i leave the key forward the check engine light stays on. i jumped it to see if that would crank it but still no luck. :confused::confused:
 

·
Registered
2003 chevy trailblazer_ls
Joined
·
25 Posts
Discussion Starter · #10 ·
just throwing it in the air...would this work if my battery went dead and when i leave the key forward the check engine light stays on. i jumped it to see if that would crank it but still no luck. :confused::confused:
The SES light is suppose to stay lit with the key forward to the on/running position until the truck officially is fired up.

The bad news is that my friend, the ASE mechanic, implies it would not work if your battery dies as you may know, once a dead battery or disconnected battery occurs, the pcm loses its memory settings, meaning the security relearn remains uncomplete/erased, even if you jump start it. You would have to start the process all over again.

The trick to keeping the battery juice high enough to start is simply to bypass (turning off) the automatic daytime running light function at the beginning of each cycle.
 

·
Registered
2002 non_gmt360 other
Joined
·
1,069 Posts
When I did the security learn, I simply connected it to a battery charger and only left it on low, along with turning off the auto headlights and radio and heater.
 

·
Registered
2003 chevy trailblazer_ls
Joined
·
25 Posts
Discussion Starter · #12 ·
When I did the security learn, I simply connected it to a battery charger and only left it on low, along with turning off the auto headlights and radio and heater.
I do not own a battery charger, just a set of good old jumper cables. But yes, if you have one, might as well use it, right?
 

·
Registered
2002 chevy trailblazer_ltz
Joined
·
37 Posts
I have tried this six-time process but no luck getting the truck started... :(

Is it anyone out there NOT successing to fire up the engine after a PCM swap?

//Pelle
 

·
Registered
2002 non_gmt360 other
Joined
·
1,069 Posts
Did you follow the times listed in the instructions? It is very important to not try and rush it. I let it sit a bit longer then the instructions asked for.
 

·
Registered
2002 chevy trailblazer_ltz
Joined
·
37 Posts
Yeah, it doesn't matter if I let it sit for 11 or 22 mins.

I have talked to PCMforless and they think it got damaged during the shipping to Sweden...so I will send it back and get another one.
That's good...but it still sucks a little. :)

//Pelle
 

·
Registered
2002 chevy trailblazer_ltz
Joined
·
37 Posts
No luck with the new PCM either...the engine just wont crank at all.

About to give up now with core PCMs...I guess I have to wait 'til summer so I can drive my summer car instead and send in my original PCM for tuning.
But shipping costs are not cheap either.

I'm not blaming PCMforless at all, I guess my car is haunted or something. Most of my stuff is. :crazy:

//Pelle
 

·
Registered
2002 chevy trailblazer_ltz
Joined
·
37 Posts
Dragging up old thread...I know. :)

But I STILL haven't been able to start my truck with the PCM4Less pcm.
If I install it and turn on the key, all I get is a security symbol blinking at me, truck won't engage starter at all.

Is the engine supposed to crank the starter when you do the security relearn?
It has never done this for me...not one time.
The PCM has been laying around in my garage for over a year now...would really like to get it up and going in the car... :worried:

Anyone with suggestions?

//Pelle
 

·
Registered
2006 chevy trailblazer_ls
Joined
·
121 Posts
I am expecting mt tuned PCM from PCMforLess today and I want to verify one part of the instructions.

PCMforLess has these instructions:

1. Attempt to start the truck by turning the key to the Start/Run position. Try to
crank the vehicle.
2. Observe that the vehicle fails to start and the security light is illuminated.
3. Release key to the ON/RUN position (not the ACC position or OFF)
4. Allow the vehicle to sit with key in the ON/RUN position for no less than 11
minutes. Security light will turn off after this.
5. When the light goes off, turn key to OFF position and allow the vehicle to
remain in the OFF position for no less than 30 seconds.
6. Repeat #1-#5 for four cycles or until vehicle starts.


I bolded the #1 part in step six as this is what I was wondering about.

Do I TRY to start the engine after every 11 minute / 30 second wait and keep doing it until it starts ?

IIRC most other instructions here on Trailvoy seem to imply that you only switch between on and off and then AFTER the 4th cycle you try to start the engine.

Can someone clarify this me? I want to make sure I am not hosing anything up if I try to crank after every cycle.

Thanks !
 

·
Banned
2003 gmc envoy_slt
Joined
·
7,190 Posts
I am expecting mt tuned PCM from PCMforLess today and I want to verify one part of the instructions.

PCMforLess has these instructions:

1. Attempt to start the truck by turning the key to the Start/Run position. Try to
crank the vehicle.
2. Observe that the vehicle fails to start and the security light is illuminated.
3. Release key to the ON/RUN position (not the ACC position or OFF)
4. Allow the vehicle to sit with key in the ON/RUN position for no less than 11
minutes. Security light will turn off after this.
5. When the light goes off, turn key to OFF position and allow the vehicle to
remain in the OFF position for no less than 30 seconds.
6. Repeat #1-#5 for four cycles or until vehicle starts.


I bolded the #1 part in step six as this is what I was wondering about.

Do I TRY to start the engine after every 11 minute / 30 second wait and keep doing it until it starts ?



Thanks !
Yes :yes:
 
1 - 20 of 45 Posts
Top