SOLVED! No Crank / No Start

[budwich]

you can likely solve that mystery but just unplugging the thing.

In addition, you refer to checks that you have done visually (eg. connector is fastened securely). You need to do electrical checks of continuity to ensure that the path is making its way into the far end device. These are done at both ends independently. First by unplugging one end, do the check. Then replug and unplug the other end and do the check. Go from the results and circuit design.

To this end, go to the bcm, locate the security signal pairs (low / signal) and do a resistance measurement across that pair.

Of course, you could likely solve the whole thing if you can get someone with a tech2 to talk to the bcm.

 

[TJBaker57]

They all have an immobilizer.

Which then casts doubt over the accuracy of schematics showing with and without....

 

[mrrsm]

Sometimes its hard to relate the Electrical Schematics to the actual locations where all these Damned Grounds are situated on the SUV Engine, Body and Under-body. Thankfully, @Realism posted them all here:

Electrical Ground locations

While troubleshooting a bad ground I came across some scans of the service manual regarding electrical ground locations for our platform posted on another site. This includes both short and long wheel base, as well as both 4.2L and 5.3L. Credit goes to Wex...

gmtnation.com

 

[Scry0402]

Thanks again for all the great input today you guys. I really do appreciate it.

I'll do some checking this afternoon on all of this stuff.

I reviewed the resources you provided and some additional ones, specifically a video titled "Diagnosing GM Class 2 Network" by Trained by Tech. In that, he said in order for the DLC to send the 7v circuit, the PCM and/or the BCM need to be online and active.

Apparently that class 2 network is a single wire network. Given that my radio works, and that the DDM are powered which are both on that network that should be an indication that the network has signal. In the video shared by @MRRSM the gentleman doing the diagnostic work indicated that all this individuals stuff on that class 2 network wasn't working. Radio, DDM, nothing.....

I'll post later with some more updates after I'm able to do some more work on it.

Thanks,

Ryan

 

[TollKeeper]

I have an idea, that might not work, but its worth a shot. This will be a 2 handed procedure. Take the original key, the one that wont work in the ignition, and hold it right next to the ignition, then using your second hand, try and start the truck with the second key in the ignition.

 

[Scry0402]

Thanks again for more suggestions guys.

@budwich - I checked for continuity of all grounds at ground plug 201, all had continuity. Also made sure of continuity on G102.

@MRRSM - Class 2 Data seems to be operational the way it should be. I've got voltage no higher than 5v on the instrument panel plug at the class 2 circuit.

I tried the key thing, no luck. I removed dash pad, tested IGN voltage and Bat+ voltage, all good there. Still a no crank with that disconnected.

Thanks again, but it looks to be Tech2 time.

Ryan

 

[budwich]

you need to check the "pair" that I suggested going to the BCM. Without proper electrical, the bcm will not allow a start to happen.

A tech2 will tell you what state the bcm is in BUT it will also tell you what the "key code" that it is receiving is... if any.

 

[Scry0402]

One last thing.... Do these vehicles provide a higher pitch "chirp" prior to the normal chime when key is stuck into ignition?

This vehicle has a noticeable chirp that I haven't heard on any other cars in videos you've all shared with me, it might mean absolutely nothing but it's not something I've heard when others put their keys into the ignition.

0 new items by Ryan Schleicher

photos.app.goo.gl

 

[Scry0402]

Also, doing more inspecting under dash tonight, found this item, anyone know what it is?

The picture angle is me kneeling into truck on drivers side looking towards the passenger side. The best view is looking through the holes in the metal bracket which supports the hush/kick panel.

It's mounted behind that bracket from that angle kind of wedged between that bracket and what becomes the center dash/console area.

I've attached some pictures for you to view. Two pictures are a side view, the closeup is from underneath looking up.

Thanks,

Ryan

 

[Mathoran]

Looks like an actuator for the A/C

 

[Scry0402]

Did more research, found out that part is an air door actuator.

Still unsure about that "chirp" though.

Thanks

 

[Mooseman]

I've never heard a chirp like that before. Do you have an aftermarket radio by any chance? Or it could be a remnant of a remote starter.

 

[Scry0402]

No aftermarket stereo @Mooseman

Your second point are my thoughts as well. The sound comes through the car speakers and not independent on its own.

Thanks,

Ryan

 

[TollKeeper]

I hate to keep going down this road, but I gotta ask. In the video you had above, I dont see the VATS module that sits on the end of the ignition switch. If thats not in place, it wont have a way to send and receive its code to the keys.

I also know what that chirp is. Its either the navigation radio (if you have one) as a function key is being pressed, OR, the programming feature on the drivers door is being activated. If your pressing the lock/unlock/whatever (I have not done it in forever, so I dont remember how its done), it makes that tone for an audible recognition of going into programming mode, OR, a button is being pressed for seat memory. But since your not pressing the buttons, something is going on there.

 

[Mooseman]

I hate to keep going down this road, but I gotta ask. In the video you had above, I dont see the VATS module that sits on the end of the ignition switch. If thats not in place, it wont have a way to send and receive its code to the keys.

There is no key code or chip. No NA GMT360, except the 9-7x, have a chip, known as PassKey3. Our trucks have PassLock. If the key cylinder is bypassed or damaged, the sensor inside will not send the signal.

 

[TollKeeper]

There is no key code or chip. No NA GMT360, except the 9-7x, have a chip, known as PassKey3. Our trucks have PassLock. If the key cylinder is bypassed or damaged, the sensor inside will not send the signal.

I stand corrected.. To many GMT's in my stable, and only 1 is a 360, my brain got a little confused. The other 2 I have, that Sensor sits on the ignition ring. Sorry about that.

 

[budwich]

The "key code" that I referred to was a signal (electrical not data) on the pair. It is stored as a "reference" so that the BCM can compare what it is seeing in subsequent key uses (or not in the case of a "theft attempt"). If the pair has no "sanity" electrically, it is unlikely that the BCM will ever be able to compare to get a valid start to authorize the pcm to start the truck.

 

[mrrsm]

FWIW... eBay has an Under-Dash Harness for a 2002 Trailblazer LT for under $100.00 that could come in handy as an Analog for Comparison, Replacement and Repair should the Harness in there now prove to be FUBAR:

2002 Chevrolet Trailblazer LT Dash Harness Dashboard Wiring Harness 15083553 | eBay

Find many great new & used options and get the best deals for 2002 Chevrolet Trailblazer LT Dash Harness Dashboard Wiring Harness 15083553 at the best online prices at eBay! Free shipping for many products!

rover.ebay.com

 

[Scry0402]

I too stand corrected. We went out to our local salvage yard and got a PCM from another 03 Trailblazer, for little $$. Put it in this morning, still just get the SES light and battery light with no crank. No dash indicator lights.

A little more info as well on just a few more tests we did. These were done with old PCM in Truck:

1) If you push the trip button on instrument panel you can get the odometer to show up and read the mileage, but it goes out after just a few seconds.

2) With the key on, when the truck is put into reverse the reverse lights on the tail light fixture do not illuminate.

This morning I also pulled the key lock cylinder out just to look at it. Interestingly now when I got to put the lock cylinder back into the truck, I cannot get it to release the key.

Wondering if something is messed up with that lock cylinder. I might be mistaken, but I thought installing that thing was as simple as sticking key in, lining it up, and pushing it in.

 

[Mooseman]

Normally you would need a security relearn when you replace the PCM. To confirm a security issue, the security light would come on and stay on to tell you. You are not getting that light I assume so doing such a security relearn now probably would be pointless but you can try it anyway.

2) With the key on, when the truck is put into reverse the reverse lights on the tail light fixture do not illuminate.

Still pointing to a power issue.

 

[budwich]

you are not getting battery to the key / park lock solenoid (along with some other missing voltages) and that the key is not in the lock position for removal. IGN 1 voltage is likely involved along with messages from thePCM to the BCM to light the lights.

 

[Seeker469]

I just skimmed through the thread without reading everything, but Ill throw this out anyway.

I had the no crank no start issue myself years ago. On the verge of pulling my hair out after testing every fuse, wire, harness..etc it turned out to be the transmission position switch. Darn thing thought I was trying to start while in gear. It had other ideas.

 

[Scry0402]

Just thought I'd update this thread and let you all know I broke down and had a shop look at it in my town.

Problem with the vehicle was in the ribbon between the BCM and rear fuse block.

Problem solved. Next on the agenda is to review how to get warm air to blow out of the rear vents.

Thanks for all your help on this all.

Thanks,

Ryan

 

[Chizzy]

I didn't reply, too far out of my skill set. Followed the whole time though. Seems simple, but I would have never found it. Glad it's fixed.

 

[Mooseman]

First time I've heard of that.

 

[Reprise]

Problem with the vehicle was in the ribbon between the BCM and rear fuse block.

Glad you got it fixed (sorry you had to have a pro do it, but sometimes we have no choice)

Any visible damage on the ribbon, or did you get a chance to see it / get the old one back ?
Just curious.

 

[budwich]

likely that the power mode contained in the bcm was not in the right state which then caused it to not allow the pcm to start. A tech2 dump of the value potentially would have shown the state / mismatch. Glad it is now working.

 

[TJBaker57]

Problem with the vehicle was in the ribbon between the BCM and rear fuse block.

By an almost unbelievable coincidence...I have been assisting a fellow on a GMT360 Facebook group with an issue of the 4WD selection switch indicator lights not working. Just this afternoon he reported it solved..... Diagnostics led us to......a ribbon cable from the BCM to rear fuseblock!! (Dimming function for the 4wd, front foglight indicator, and headlight on indicator is handled by the bcm) Looked like something spilled into his connector there.... Fortunately he has a parts truck to grab fromn

 

[Redbeard]

"Looked like something spilled into his connector there.... "

One more reason not to drink and drive!

 

[TJBaker57]

One more reason not to drink and drive

Especially if you are driving from the back seat where this is!

 

[mrrsm]

BCM = "Bad Coca-Cola Moment"... (Great Pics....)

 

[rolo95]

Just thought I'd update this thread and let you all know I broke down and had a shop look at it in my town.

Problem with the vehicle was in the ribbon between the BCM and rear fuse block.

Problem solved. Next on the agenda is to review how to get warm air to blow out of the rear vents.

Thanks for all your help on this all.

Thanks,

Ryan

Ryan,
can you post a pic or 2 on that BCM ribbon
and what was the problem, did you replace the ribbon or just cleaned it ?
Thanks
Rolo.

 

[TJBaker57]

I see the part is listed as no longer available.

Here is a link to a thread where someone repaired theirs. I also see the item listed on eBay.

BCM Body Control Module Cable Repair How To 15077187

BCM Body Control Module Cable Repair How To Part Number: 15077187 The ribbon cable for my BCM somehow got a crease in it, and some of the circuits were left open. I could press on the ribbon cable a certain way and the dome lights would flicker, radio would turn off, etc. I called the Dealer...

gmtnation.com