2007 NBS 3500HD No start , no crank

[chambie]

Hello
I have a very strange situation with my truck. All was well with it... pulled it out of my garage, went out about an hour later, started it up and pulled it back in. Got up for work the next am, jumped in , and no start , no crank. I noticed the dash voltage gauge was at 0.. Service 4 wheel drive message was lit, along with the abs light. No chimes when i opened the door, no courtesy lights. I put the truck on the charger and let it charge for a day.. Tried to start it.. no change.. no battery voltage showing on gauge. Got new batteries and installed... no change. Cleaned grounds under driver door... no change. Also showing codes for glo plugs.. po671 to 678. I have also learned that half of the fuse block under the hood seems to have no power. Pulled fuse block off and don't see any issue there. When i turn the key to on, the gauges don't sweep.. no courtesy lamps, no turn signals, front windows work but rear windows don't. I haven't gotten a chance to look at it further but plan to today... i'm thinking maybe a wiring harness ? Or Computer issue ? I really have no clue yet... Anyone have any experience with this happening ? I appreciate any insight someone may have .. Thanks in advance.
Lindsay

[DmaxMaverick]

A few things come to mind. I don't have a diagram for your rig, so I'll make a guess or two. The codes are likely collateral to the power loss, and probably only indicates the related systems are missing power. A good indication that the PCM is doing its job.

(in no specific order)

Check fuses.

Any evidence of rodents? If you find any, anywhere, damage is possible where you can't see. Comprehensive insurance, if you have it, almost always covers rodent damage. I've been there a few times.

What you describe sounds like battery(ies), ground, or terminal failure. Did you notice any corrosion when replaced the batteries? Are the headlamps getting full power? All accessory feeds have fusible links that can fail, but that's usually an indication of a significant downstream short. When they fail open, the insulation will almost always show overheat, brittle, or deformed. The battery cables can fail under the insulation and look fine outside. Also check the power lug at the starter solenoid. If loose or poor contact, it can effect starting and some accessories. Does anything change when you turn the key from ON to Start (other than some accessories powering off, but instrumentation should remain powered)? If power dips, flickers, or breaks during a start attempt, it's likely a weak battery cable connection. It may also have a secondary accessory feed at the crossover cable, at the "jump start" box, so check that it's well connected.

Try swapping the relays in the underhood power distribution panel. A failed relay will have the power loss follow the bad relay. There may also be relays under the dash near the brake pedal, and in the dash fuse panel. An electrical diagram would be very helpful identifying the system that's missing power. Some systems are reliant on power from other systems as they power up (daisy-chain), so a failure of one can cause power loss downstream to other systems.

Ignition switch. It's multi-poled and multiplexed, meaning it has several, separate poles for different systems, and they power multiple channels, most of them relayed. If some accessories never get power at any switch position, switch or harness connection failure is possible. Check the connector for evidence of damage/overheating.

[chambie]

Thanks DMax… no evidence of rodents so far. I am in the process of checking fuses and such, and swapping relays. I also will track down other grounds to check. I don’t have a diagram for it either…so far the fuses in the cab on the drivers side check good.. yet the things they control do not work… under the hood there are fuses that are dead, but the fuses are good.. headlights are full power and do not dim or blink when you turn the key. Everything stays powered up when the key is turned. I haven’t checked the ignition switch yet.. thanks again for the reply… I’ll let ya know if I come across something

[DmaxMaverick]

When the ign. switch is turned to Start, some accessories should power off, such as the radio and HVAC. If they don't, the switch, or its harness, is suspect. Do they get power at key ON? Maybe make a list of what gets power and what doesn't, at key ON, and what changes happen at Start.

[chambie]

Ok . I will check. I know HVAC and radio power up at key on.. I'll check when turned to start

[chambie]

When the ign. switch is turned to Start, some accessories should power off, such as the radio and HVAC. If they don't, the switch, or its harness, is suspect. Do they get power at key ON? Maybe make a list of what gets power and what doesn't, at key ON, and what changes happen at Start.

No luck today finding anything blatantly wrong. Checked all the chassis grounds i could find and get to. I tried to get to the ignition switch, but can't figure out how the bottom plastic trim under the steering wheel comes off. I'm guessing the release to adjust the wheel must come apart, but i didn't see how so i didn't try. Nothing looked bafd that i couyld see , and i didn't test it as i couldn't see the contacts.

Here is a list of what is happening :

Key on :
No gauges sweep or move
Radio on
HVAC on
No turnsignals
No brakelights
Horn works
Front windows work
Rear windows don't
Mirrors work
Seats work

Turn to start :
HVAC stays on
Radio stays on
No crank,
No start

No evidence of critters... truck is in a climate controlled garage.. doesnt mean something couldn't get in it for sure... but i haven't seen any sign yet.. frustration level is rising as i can't find much info out there on causes yet... the switch makes sense to me.. as everything was fine when i backed it into the garage on Sunday night. And Monday morning the issue was there Outside of the engine starting, the only thing that moved was the tires and the ignition switch !!!

[chambie]

Update
Bought a new ignition switch and changed it. Still the same problems....

[a5150nut]

Update
Bought a new ignition switch and changed it. Still the same problems....

Are you talking about the key cylinder or do you have a box down on lower end of stebox to work it.ering column like earlier models ?
It would have a rod from the key cylinder to work it.

[DmaxMaverick]

The brake lamps are concerning. They should work, despite anything else, and the signals should work with the key on. Do the hazards work?

The seats, mirrors, and horn are powered independent of the ign. switch.

There's an open IGN circuit. Either one of the IGN fuses are blown, relay(s) not switching, or the harness is open somewhere between the ign. switch and relay. The brake lamps are a separate problem.

[chambie]

I changed the electronic box for the switch. Key cylinder is the same.

[chambie]

The brake lamps are concerning. They should work, despite anything else, and the signals should work with the key on. Do the hazards work?

The seats, mirrors, and horn are powered independent of the ign. switch.

There's an open IGN circuit. Either one of the IGN fuses are blown, relay(s) not switching, or the harness is open somewhere between the ign. switch and relay. The brake lamps are a separate problem.

The Hazards do not work. No turn signals.Headlights work and so do the run lights. One thing i noticed yesterday... I switched the radio to XM, and it said it was in theft lock ?? would that be because of the weirdness going on ?
I'll keep searching ! I swapped relays and it didn't make a difference..Is it possible the transmission doesn't know what gear its in ?

[DmaxMaverick]

The theft lock is likely due to the missing accessory power. Theft lock can prevent starting, but not the rest of the problems. I don't think this is an electronic issue, but rather a physical power supply failure. Any tranny issues will likely be a result of the power problem, and not the cause of it.

This is sounding like a loss of power for an entire accessory feed. Something has been disconnected, damaged (by whatever means), open fuse, or fusible link fried. I also wouldn't rule out a failure of the power distribution panel, itself. Check the underhood fuses for power again, specifically the large IGN's (40A+), and any IGN fuses (there should be several). I located the upfitter electrical manual (https://www.gmupfitter.com/wp-content/uploads/2021/05/2008_LD_ElectricalPickupsChassisCabs.pdf) for 2008 (2007 is more complicated, being the transition year). It's over 600 pages and covers many applications, so it may take a while to chase the circuits related to your problem. From what I can tell, so far, it appears that primarily, if not entirely, the right half of the power distribution panel is not powering downstream. There has to be a common point of failure. If you're seeing power at the panel, there must be an interruption of a large harness immediately downstream, before it distributes to the independent systems. Something must be unplugged, or separated in some manner.

[chambie]

Yes i agree... Unfortunatley i haven't been able to locate it yet.... There seems to be power missing on parts of the fuse block.. but not knowing how it all feeds it's slow going. All the fuses and such test good so far

[DmaxMaverick]

Download the PDF I linked. Beginning at B-5 is the power distribution panel, fuses, relays, and all of their downstream circuit associations. Also note, many of the circuit protections are PCB integrated into the panel, and are not externally visible, or serviceable. I don't know if they can be individually repaired, or if they are accessible at all (potted or otherwise sealed). A failure of any of them suggests the power distribution block, itself, has failed.

Many of the failures you are experiencing are related, directly or downstream, to the RUN/CRNK relay. Verify that relay hasn't failed by swapping it with an UNRELATED circuit (one that currently works). Also verify power to and through the LBEC1 and MBEC1 fuses (~60A), which powers it and the other problem circuits downstream.

[chambie]

DMax Thanks... Would it be out of place to speak to you on
the phone ? If not and you have a couple minutes would you give me a call at *** ? If not I understand.. It appears all the ignition fuses and relays are not getting power in the fuse block.

[More Power]

There are numerous switches that together comprise the ignition switch. One or more of these individual switches could be intermittent or open. This happens occasionally in trucks that see a lot of off/on operation, like delivery vehicles or just many years of operation.

[DmaxMaverick]

There are numerous switches that together comprise the ignition switch. One or more of these individual switches could be intermittent or open. This happens occasionally in trucks that see a lot of off/on operation, like delivery vehicles or just many years of operation.

Traditional GM ignition switches were left behind in 2006. Later (2007.5 M/Y) ign switches are serial data transmitters. Turning the key communicates the key position (as well as system access authentication: the security control) with the BCM, which then commands relays throughout the various systems. The actual "switch" is within the BCM. Traditionally mechanical processes, such as powering the systems on, and starting, are logically processed. The last "physical key" ignition system I've had was in the 2014 Cruze, which had the same type 2007+ ignition system. Turning the key seemed normal (traditional), though it was only an emulation of what was previously normal. Turning the key to ON would power up like the older systems, and turning the key to Start would crank the engine, but it was more than only that. If you were to "bump" the starter, like you would to (traditionally) only rotate the crank a little, the "START" process will complete, rotating the crank until engine start, or until it is interrupted by either a failed start, or a Key-Off. While the key switch can fail to communicate properly, or at all, there are essentially only a fraction of moving parts to fail, and no significant load carried by the switch (<5V signal). The ignition switch, in this case, was replaced with no changes to the problem. Fortunately, modern ignition switches are still one of the least expensive and easiest to replace components of the system.

[More Power]

the "START" process will complete, rotating the crank until engine start, or until it is interrupted by either a failed start, or a Key-Off.

So, putting a 3/4" flex-handle and 36mm socket on the damper bolt, then bumping the starter to help loosen said bolt wouldn't be a good idea in the new(er) trucks? Not that I've ever done that... ;)

Incorporating "ign switches are serial data transmitters" may be related to push-button start in these sorts of automotive applications. As Scotty said: "The more they overthink the plumbing, the easier it is to stop up the drain."

[DmaxMaverick]

No, I wouldn't recommend that. You could still jumper the starter solenoid, though (key Off/out, of course).

As far as over-thought plumbing goes, they have been extremely reliable, compared to the old school standard. This is the first failure I've heard of, outside failed relays or harness damage. Unfortunately, some will fail, and when it's you with the fail, extremely reliable exits the scene.

[chambie]

Update on Truck.... It's alive again !! The BCM had failed. After checking all grounds and harness's and looking for any signs of damaged wires, it lead me to believe it was the BCM. I ordered a pre programmed one and it arrived today. Swapped it out and all is back to normal at this point !! What a relief ! Thank you all for your suggestions and help !! It is greatly appreciated

Lindsay

[Yukon6.2]

Right on
Thanks for posting the end result.
That helps others when looking for answers.A lot of the threads are never finished off with results and solutions.