If we can successfully get the data we 'may' see why this happens. Maybe we will see messages from the BCM causing this activity. It would take some sluething and guesswork since we don't have access to GM proprietary information and as such we cannot decode ALL the messages but it may be enough to help identify an issue.
05 Envoy XL 5.3 Won't Crank
- Thread starter EnvoyMan
- Start date
If we can successfully get the data we 'may' see why this happens. Maybe we will see messages from the BCM causing this activity. It would take some sluething and guesswork since we don't have access to GM proprietary information and as such we cannot decode ALL the messages but it may be enough to help identify an issue.
Everything has limitations. Reminds me of a line from a Clint Eastwood movie... "A man's got to know his limitations."
In post #69 the third image of his scantool screen depicts reading trouble codes from the BCM so there must have been some communications possible there or it could not have read the BCM trouble codes.
Hey, I just found something. Pin A19 on the ribbon connector for the BCM never gets power no matter what the key position is. Ignition 0 and 3 do get power depending on the key position. Is Ignition 1 supposed to come FROM the BCM? I tested these with the ribbon plug out. I also realized the orientation of the diagram vs the actual connector is a bit weird so I had to rotate my phone for the pins to match the picture.
I got the serial app, but when I try to connect to the MX+, it fails saying socket might be closed or timeout. It says that after 15 seconds so I think it timed out. How do I get it to work?
I think ign1 is provided as a result of "keying".... and goes to the BCM. As shown in the PDF that I posted a bit back.
Gotcha, is the ON key position between ACC and START considered the RUN position? I’m not seeing the RUN position explicitly mentioned as a key position so I want to make sure. If that’s the case I’m not getting ignition 1 in RUN.
Yes. The RUN position is where the key would be at the second detent felt as the key is turned towards the crank/start position. Fuse #16 TBC1 in the underhood fusebox should be hot in this position. That is where the power goes through on the way to the A19 pin at the BCM
edit: the power will flow through fuse 16 then back to the rear fuseblock and feed from the rear fuseblock up through the ribbon cable to the BCM.
Does the radio unit pair with the MX+ succesfully BEFORE using the serial terminal app? And does the MX+ show in the "devices" menu item in the serial terminal app?
Here is another thought. You say the radio has Torque installed? If Torque is active even in memory it does not release the bluetooth connection to the MX+ device So Torque would need to exited using the Torque menu item for quit. Just backing out of Torque does not close the app and release the bluetooth device connection
Do you know which fuse in the rear block carriers power from tbc 1? I just checked tbc1 at the run position and it had voltage and both ends.
I caved and bought an ONN android tablet, and it’s doing the same thing where it pairs successfully, connects and then drops out after a few seconds.
So if I understand the question here... you have power at both sides of the underhood fuse 16 (TBC1) but not at the ribbon cable A19?
The power does not go through a fuse in the rear fuseblock, it only passes through from a connector beneath the rear fuseblock to the socket for the ribbon cable.
You need to adjust the "newline" character setting in the serial terminal app. It will be a bit of trial and error. Looks like these choices...
Even without line breaks I can easily see the PCM, BCM, LGM, PDM, DDM and others sending their awake messages indicating they are alive and well. They send these messages like every 2 seconds.
EDIT: I also see the cluster.
Any luck testing for that TBC1 power from underhood fuse 16 back at the ribbon cable? That is key right there. MUST have 12 volt power at that A19 terminal. Test in the base of the ribbon cable to see if it is feeding into the ribbon cable from the fuse block socket
I’ve posted a paste in link with a length of data in it. https://pastebin.com/8v2WvZZQ
How do I get to that? I can’t figure out a way to get to the BCM as there are plastics in the front of the seat
So right there I can see many modules sending there awake status. The 3rd byte in eachessage is the address of the module sending the message. Just listing the ones I know straight away... A0 is DDM, A1 is PDM, A2 is LGM, 11 is P M, 40 is BCM, 60 is IPC, 89 is either radio or amp or similar.
All messages in that screen are nothing more than network status messages, the vehicle network is pretty much idle with no real.activity there right now.
We can explore more later but the main focus right now should be getting the imteruption of 12 volt signal on A19 resolved. That absolutely must have that signal of 12 volts at BCM ribbon cable terminal A19 with key in RUN
As a sanity check, it’s supposed to go B1-B20 on the side you’re seeing from left to right, and A1-A20 from left to right on the “back” side, correct?
Also, that pastebin data was with the key in the ACC position, not RUN so that hopefully looks right that they’re all idle correct?
You should be able to access the base of the cable in place like seen here. Look for the gold contact strip.
The other end is seen here...
That is correct, after some time has passed in the ACC position the bus quiets down. At first turn of key from OFF to ACC there is a flurry of activity from BCM, IPC (cluster), and others.
So that was my bad, pins A18-A20 all have power in the run position
A new revelation. I’ve recorded a video which will take a while for my phone to upload, but if I push the ribbon connector into the bcm more, the park lamp relay clicks on, which is relay 30. OH MY GOD, I just took a closer look at my IPC on the video and I saw my voltmeter turns back on too as well as the fuel gauge! I haven’t been able to get the voltmeter to turn on. Is this my issue?? The reason I haven’t been able to get a closer look is because it’s storming all of a sudden so I’m stuck inside my car.
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Well crap! I thought we had something there! Oh well...
So in the app, to be able to record and later access a logfile we need to set a save+log file location and give the app Android permission to use that folder. O think that starts with the settings menu selection in the app, then under misc is the selection for " save + log folder". Select "custom" then navigate to a folder that you have access to with whatever you use to view/copy/whatever a file. On my android there is a "use this folder" button to grant access for serial terminal app to use that folder to store files. If this is not dome the app will save to an internal folder that you don't have access to outside the app.
After the save folder is setup back at the main terminal app, up at top right is the three dot menu button. press that, select "Data" then checkmark the "log" item. This will save all of whatever is onscreen. Uncheck the box when you are done recording.
I would want to see a sequence recorded from key out, everything off then insert key, pause maybe 5 or 10 seconds, turn key slowly to the first click (ACC) and again pause for a ten count, then turn the key to 2nd click (RUN) and again pulause for a ten count, then turn key to start, pause briefly and let the key come back to RUN. Pause again and follow the same sort of turn key, pause, turn key, pause all the way back to key OFF and removed.
This would give us (mostly me) a baseline to look over to see if I see anything that just jumps out as wacky.
Then perhaps record a session where you have the dash lights mostly working yhen add the BCM back in and the cluster goes wacky again. This was in the RUN position, correct?
So I was able to get the voltmeter to turn back on, and it looked like the car was ready to start. AS SOON AS I pushed the key to crank, I lost all power and my key was stuck in the ignition. I had to push up the little cylinder in front of the ignition cylinder to remove the key, and holy crap, that thing was scalding hot! Should this little cylinder thing be super hot?
Any idea why I could have lost all power suddenly?
Any idea why I could have lost all power suddenly?
It is known to get hot. I don't know if it should but mine does get quite warm. Maybe someday I will test the current draw on that little sucker.
I tightened my battery terminals even though they were pretty snug, and I reinserted the fuel pump relay because I wanted to prime the oiling system first and it started up. Forgot I had half the ignition coils disconnect so after getting those back in it’s even “smoother” now. The only issue now is that I can’t get the truck to move :/ I had all functioning gears before I did the DoD delete
Geez, some people want everything!
Maybe check the power feeds to the TCM and shift solenoids etc.
Does it even try to move?
When I put it in drive once, it inched forward a little bit I put it back into park. Since then none of the gears did anything.Geez, some people want everything!
Maybe check the power feeds to the TCM and shift solenoids etc.
Does it even try to move?
Edit: to add on, the linkage is definitely fine since we’ve been able to put it in neutral for towing
Did you tow this in neutral with rear wheels on the ground? Is this a 2wd or 4wd model? If 4wd was the transfer case in neutral?
It was always towed with all wheels raised. It is 4wd but I couldn't put the tcase into neutral due to the power issues. The motor on the tcase makes noise when I shift it and the knob does show that it has shifted, so I'm confident it is fine.
The first time I tried to get this towed I couldn’t get it to go to neutral as I forgot I had disconnected the shift linkage to change the transmission pan and oil, and I was in a rush to get it towed for personal reasons. The rear wheels would drag if the envoy was inched forward after a few degrees of turning, and then we figured out the linkage issue and it went to neutral fine. The PCM sees the shifts (suddenly the PRNDL, DIC, and HVAC screens have gone dark??) as I can hear the idle change slightly when I shift gears. Obviously, this doesn’t necessarily mean the transmission wants to comply.
Sorry for the late response, my phone died.
EDIT: fixed some readability
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Have these remained dark now?
The ribbon cable,,, had that been disturbed at all during the DOD delete? Just wondering how it lost connection somehow before you discovered that pushing it in more did the trick to get the cluster lights etc back. Perhaps consider a good inspection of both ends of that for signs of corrosion? The A side shown in your picture of it looks good though. If you need or want to get it out and the longer plastic end off for a close look I can advise how that comes apart.
Sorry I don't really know squat about automatic transmissions. Maybe someone will jump in here with some advisements on how to proceed with troubleshooting there. The PRND321 display indication is a result of the range switch(es) where the linkage connect and these connect to the PCM. The PCM sends serial data messages to the cluster to move the indicator bar under the PRND321 display, there is no mechanical connection there. So if there is any way for the range switch to get moved by the linkage while the actual shaft from the trans doesn't move then then the display would move while the trans didn't shift I guess?? I'm totally guessing here as I actually have never even looked at trans shift linkages!!
So I could always see the PRNDL screen when the no crank issue was at its worst, and the DIC and the HVAC screens only came back on when I removed the comb. Then when I fixed the BCM wiring initially all 3 displays worked, but all of a sudden none of them work.
On the other hand, I may have made a mistake with the transmission. I changed the trans oil pan (made sure I got the deep pan like I originally did, but with a drain bolt) and I filled it with 4qts like the job called for. When I put the dipstick back in to get a fluid level, it got stuck and I had other issues to deal with (like the car not starting) so I left it. Last night, I finally battled with the dipstick and I won, only to find that the dipstick was completely dry. Not a drop of oil. I know from when I changed the pan that the stick doesn’t go all the way down, but I was horrified to say the least. Ran to get some more valvoline trans oil and I’m filling it up today. No trans leaks to speak of.
I did not, however, account for fluid lost through the transmission cooler lines when the car had been worked on, and I’m wondering if the car sitting for months allowed more fluid to drain back into the pan, which was subsequently lost when the pan came off. Getting the pan off was… messy to say the least so I didn’t get an exact measurement of how much came out.