2004 Trailblazer- No start, no crank

[Epdx]

Good morning!

After replacing the BCM and having it reflashed at the dealership, my vehicle won’t start or crank (before replacing the BCM it would start immediately when jumped). The battery is new.

My first instinct was a possible anti-theft code was preventing it from starting, but upon reading through some of these posts, I realize that the solution is unlikely to be that simple. Drat.

Despite that reality, any advice would be appreciated. The vehicle is currently stuck at the dealership, but I’ll be having it towed back to my house and can try some basic fixes (if there are any!) Thank you!

 

[budwich]

put back the old BCM... at least, then you can start it and drive it home.
The stealership should be able to tell you why you have a no start problem.
Further, go thru the "no start check"... The first of which is "turn the key to ON and leave it there... what dash lights are showing?" Go from the results.

 

[Mooseman]

Did the stealership try the security relearn? If either the BCM or PCM is reflashed, it has to go through the relearn.

huge problem after PCM update / calibration (PCM Security Relearn)

 

[Mooseman]

Another thing reading that other thread is if the stealership did the PassLock relearn? That's something that may have to be done when the BCM is replaced even before the the 30 minute security relearn.

Question: what is the security light doing?

Question 2: why was the BCM replaced?

 

[Epdx]

put back the old BCM... at least, then you can start it and drive it home.
The stealership should be able to tell you why you have a no start problem.
Further, go thru the "no start check"... The first of which is "turn the key to ON and leave it there... what dash lights are showing?" Go from the results.

I wish I had the old BCM, but I don’t…I will do those checks when I get it back.

 

[Epdx]

Did the stealership try the security relearn? If either the BCM or PCM is reflashed, it has to go through the relearn.

huge problem after PCM update / calibration (PCM Security Relearn)

I’m not sure, but I’d hope they’d know that! I am going to go in there today and will ask. They’ve been easily confused during this experience, so it wouldn’t surprise me if they haven’t.

 

[Epdx]

Another thing reading that other thread is if the stealership did the PassLock relearn? That's something that may have to be done when the BCM is replaced even before the the 30 minute security relearn.

Question: what is the security light doing?

Question 2: why was the BCM replaced?

I will ask about the PassLock relearn. The security light was not coming on when I turned the key right after the BCM was replaced, but I haven’t had access to the vehicle since the reflash.

As for the second question, the BCM was replaced because I am an idiot who saw several issues, assumed they came from a common cause, then further assumed that the common cause was a faulty BCM. I wish I’d found this forum earlier.

The vehicle had the instrument cluster woes and battery draining issues that a lot of people have reported, as well as intermittent radio, door lock, and window malfunction. All of that seemed to be something that could be explained by a faulty BCM, but I’m now wishing that I’d gone a different route in troubleshooting it.

 

[budwich]

I guess a tow is in your future. :-( Hopefully you have some knowledge of vehicles and electronics then the forum can likely figure out what's up with your "eyes and hands" and their "hands and minds"...

It will also help if you have access to an OBD device that you can use to get data from the vehicle... again, people here will help get that info as there are various posts about that kind of activity. That would have been the best route to follow at the start. It is concerning that your decision about the BCM appears to have been done without any "technical troubleshooting"... scary. Its even more concerning that the dealer didn't confirm things before heading down the "replacement / reflash" path.

 

[c good]

I recently had a no crank, no start problem. After confirming I was getting 12 volts to the solenoid, I thought maybe the starter or solenoid was bad

Took my old leather mallet and lightly tapped on the side of the starter and solenoid, turned the key and it started right up

It was good for a few weeks and started acting up again and the mallet saved me a few times

I ordered new AC Delco starter, pulled the driver's side wheel off to start the project

I noticed the heavy cables from the battery to the solenoid and solenoid to starter were lightly coated in oil and road grime.

I've learned over the years to start with the basics first so thought I'd try cleaning those connections first and re tighened everything.

Turned the key....It fired right up! Better and stronger start than I've had in years! It was just too much resistance from the dirty connections to give the starter a full jolt from the battery.

Two weeks now and no problems. Hope this helps.

 

[Mooseman]

Another thing to check is the grounds. I had mine in at the stealership I work at to have the engine mounts replaced and the main ground wires to the block was corroded enough that it broke when the engine was lifted.

 

[Epdx]

Another thing to check is the grounds. I had mine in at the stealership I work at to have the engine mounts replaced and the main ground wires to the block was corroded enough that it broke when the engine was lifted.

I will try that if the security relearn doesn’t help.

I guess a tow is in your future. :-( Hopefully you have some knowledge of vehicles and electronics then the forum can likely figure out what's up with your "eyes and hands" and their "hands and minds"...

It will also help if you have access to an OBD device that you can use to get data from the vehicle... again, people here will help get that info as there are various posts about that kind of activity. That would have been the best route to follow at the start. It is concerning that your decision about the BCM appears to have been done without any "technical troubleshooting"... scary. Its even more concerning that the dealer didn't confirm things before heading down the "replacement / reflash" path.

I do have access to an OBD, so that’s definitely part of the plan going forward.

I really appreciate the input here…this vehicle has been a learning experience, for sure.