Will the ECM, BCM, TCM, ABS, HVAC, Radio, etc communicate with your diag tool? If one or more is not you have a place to start looking.
If not.
1-Open the engine air cleaner box and make sure our snack stealing friends haven't had a chew fest on the ECM & TCM wiring. Wear gloves and face & breathing protection and don't touch your face without washing when cleaning up mouse nests. They're full of mouse urine & feces. Mice carry Hanta virus and other nasty pathogens. I usually douche things out with bleach after cleaning the material out.
2-Do you have power and ground at the diag port? Terminal 16 is battery power and terminal 4 is chassis ground.
3-Does the Class II serial and CAN data look plausible on your scope or is something stomping on or corrupting the comms.

 

I took it to the garage this morning, as I only have a small diagnostic scanner. I checked what I could with my little scanner and a circuit tester. The garage called later and told me that the car has went into theft mode. The theft mode light on the dash isnt on, so I can only go by what they are telling me. The ignition and the key itself are apparently fine but they tried to do a reset and had no luck. They are telling me that the relay/fuse box under the hood is going to have to be replaced. I don't know much about this stuff, so I don't know if any of this makes sense or if I should take it to another garage.

 

I'm not familiar with any fusebox condition that would cause theft mode - or remove theft mode if fusebox is replaced. Others will check-in.

Was there some work done on the car shortly before? Maybe a stereo swap or transmission work or anything? Looking for a typical reason for system going into theft mode.

 

From what I've researched there is no reason that a fusebox would cause a theft mode. When I went this morning to haul it back home, the theft light is now on. It hasn't had any recent work done to it. The owner before me put a stereo in it but that was almost two years ago. The car still isn't getting power to the fuel pump, starter and isn't firing. I'm not sure why the theft mode light would just now come on. The car has been doing this for a week.

 

That is odd. Ive read that some cars have gone into "theft mode" if battery was disconnected with key in ignition...however it should be able to be reset, regardless. There is a procedure im sure but maybe the shop isnt aware of this.

 

After checking all of the grounds and fuses, I tried a couple of reset procedures, and the garage said they tried as well, but still nothing.

 

No crank - no start is not usually a security problem.

The car will crank, start, and immediately shutdown when security is triggered.

Even a cheap code scanner would prove missing or present comms.

 

Thanks for the info. This one isn't getting power to the starter,fuel pump and the key switch. All power options (windows, seats ect) and the headlights still work. After almost a week of this car doing this, the theft mode light just came on this morning.

 

Sounds like the shop is looking to take advantage of your inexperience with automotives and turn it into a pile of cash. No theft light is fishy. A whole fuse box replacement is fishy.

Did you check all the grounds, both outside and inside the vehicle? Did you verify with a diagram that you checked all ground locations for tightness, cleanliness and connection?

 

I thought it was fishy too so I hauled back home this morning. Oddly, the theft mode light is now on. I checked all of the grounds, inside and out, and tested all of the relays. Everything was fine except the fuel pump relay and starter relay. I bought new relays and put in it and they are still dead. I'm still not believing that a whole fuse box would cause this. They was going to charge $475 for a fuse box but I'm not going to start throwing random parts on it without pinpointing what it really needs.

 

I don't know what level shop you took it to, or what equipment they have. Maybe it was a Dealer level and also honest joint, hey it could happen.

Looking over diagrams and thinking about tests I've done on my 2010, I have a nagging thought.

What is most likely to happen if a cracking underhood fuse box cracks further while driving?

Key on when power fails . . . theft sets and additional damage is done while vehicle comes to a stop?

It would take huge coincidental coincidences to coincidentally occur. Sorry couldn't resist 😅

 

lol..I couldn't have resisted either. The shop was recommended to me. Equipment wise, they seem to be close to dealer level. I haven't used them before, so I can't personally speak to their honesty. But they claimed the fuse box is the problem and refused to continue checking anything else.

 

It's so far fetched imo. But I'm not getting any better guesses. Maybe I would pull the battery and unfasten the underhood fuse box and eyeball every slot in all areas and both sides for damage and what-not. Take plenty of pictures before each phase.

After that I might unplug every module to clean pins etc. but it sorta sounds like you've done them all already.

 

Adding:
These particular fuse boxes seem to be plentiful -I've actually considered getting a spare just in case. And it's not as terrible as you might think to swap. I plan to watch three or four videos - there are plenty - before buying.

 

Thank you. I ordered one online for $125 shipped and I'll install it myself. I haven't came up with anything else so I figured I'll go ahead and try it. If doesn't work, I'll have a extra fusebox anyway.

 

I hope you will do a separate how-to thread with part numbers and pictures during disassembly and reassembly because this sequence for this year-range could help many who follow!

 

I'll definitely do that.

 

what about the gear selector lever? almost sounds like the ecm is thinking its in gear. (yes i know if its in gear the key is not supposed to come out, but i could pull the key out of the ignition while i was driving in my old impala) there are quite a few people that have problems with it. i seriously doubt its the fuse box. check this thread. it wouldnt hurt to check.

https://www.impalaforums.com/threads/2015-impala-ltz-2-5-dash-says-shift-to-park.1893722/?post_id=3750747&nested_view=1&sortby=oldest#post-3750747

 

I have my doubts about it being the fuse box too but with running into dead ends I figured I'd try it. The switch under the console is possible and I will check it, thank you. But, it wouldn't cause loss of power to the fuel pump, would it? On these computerized cars, nothing surprises me..lol

 

Could be.

🤔 wondering how many of the six troubles cited by the DS in first post will be solved by fixing the dashboard transmission gear indicator. Probably there's several troubles - or maybe its one or two causing all. It gonna be cool so see how this turns out.

 

The start logic reports to Module and it's entirely possible.

Your first mention:
"My 08 Impala 3.9 has developed an issue that I've never came across before. It will not crank"

Starter cranked when solenoid was jumped. So Module is not passing start-logic tests.

Transmission gear is one part of test (it looks for park or neutral).

But you already know these things and tested. Candidly I sorta thought you already did the deed. If haven't then it cannot hurt to take it off the tablw by fixing it. It's not likely to fix everything mentioned. Who knows.

 

The shop that I took it to supposedly went through and checked everything. I'm assuming they checked the transmission gear as well. Since it was mentioned, Im going to check it myself. You just never know with garages anymore. I appreciate all the info and suggestions that you all are giving me and hopefully the problem can be taken care of. I used to do all the work on my older cars, but I'm kind of lost on these newer ones and Im just learning little by little on this one as it never given me any problems until now. It's probably something fairly simple, just a matter of narrowing it down.

 

@SidC69

From my personal help files.

Here's one example video of troubleshooting the consol shift interlock. It's titled for being stuck in park but it applies to a wide swath. Also search out others on your own (for better understanding):

https://www.impalaforums.com/threads/my-2010-impala-3-5-flex-help-files.1892293/#post-3743559

 

"Update" After not having any luck getting the problem figured out, I took it to another garage in a nearby town and left the car with them. They are called me this morning to tell me that my Impala is fixed and ready to be picked up. They basically started from scratch, testing and checking everything, and they found that the problem was in the ABS module. Power was going into it, but no power coming out. I'm not sure why the first garage didn't find the problem but I'm just glad that it was found and solved and my car is back on the road. Thank you to all that commented and offered tips and suggestions.

 

I went through this a year ago on my 2010 LTZ. Removed the ABS module connector to ohm the wires for the wheel speed sensor to find the faulty one. Didn't press the connector in all the way. Thought is was. It was just a mm or so out. NCNS. The comm lines are kind of in series. That's a tough connector. If it isn't in all the way or you are missing anything from the ABS module, you will experience a NCNS.

 

Thanks for the update. It really helps others who may come across a similar issue.

 

Thank you. I hope it helps someone in the future.

 

@SidC69 you did great work diggin-into the systems and trying to pass along your thoughts and observations, there's not much you can do about the first shop's assumptions. I'm glad the second shop was competent. If future members have this sort of pesky weirdness then they owe you a cold one for sure. Nice work brother.

 

Thank you brother. I learned a lot about this car through this experience. I hope no one else experiences this problem, but when it comes to cars, I'm sure it will happen again to someone else at some point and I hope they find this thread and hopefully it will save them some time and money.

 

Thanks for the after action report. It really helps others that may run into this kind of problem.


Glad you found a shop that had a good diagnostic mechanic. Those guys are getting harder to find.

 

You're welcome and thank you. You are definitely right, they are getting harder to find. But thankfully I found a top notch garage to take mine too.

 

Check fuese

 

Grizchev do you think this might be what’s wrong with mine???

 

I just now saw this.
The system didn't ping me.
I'll look into it now.

.
It's possible and should be included in tests. Here's a jump to your original help request thread in order to keep things together. I've responded there too.

https://www.impalaforums.com/threads/2007-lt-impala-no-crank-no-start-need-help.1894944/#post-3763062

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