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I've been struggling with my 2008 SS Impala. It usually start right up and runs great but within the last year it has had an intermittent no start. Has power to gauges, heater, radio...everything inside but the engine will not turn over/crank when the key is turned to do so. After cycling the switch a couple times/sometimes a lot of times it finally will turn over and start right up. I'm not hearing any clicking noise from the solenoid on the starter or anything like that when the problem occurs.

I installed a new battery and cleaned all the connections including a ground by the battery. The issue is still happening.

I then replaced the starter relay and power train relay to see if this would help. The problem persisted and threw a DTC finally. P1682. This can also be caused by low voltage and it was brutally cold that day and the battery could have been low.

I did some reading and saw a TSB on corrosion problem with the connections to the computer. I pulled the computer and checked the connections and put it back together. Still having issue.

I decided to go ahead and change the ignition switch since they are cheap on this car. The problem persists.

It's near impossible to diagnose due to the fact I can't test anything as it usually won't fail long enough to do so. My next step is to get it up in the air and check for a bad connection to the starter but I'm really grasping at straws now. I am really hoping somebody can give some advice or has had a similar problem with their Impala.
 

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Discussion Starter #2
Something I left out and wanted to add. This car only has 35,000 Miles on it. My sister owned it before me and never drove the thing. Obviously something that makes the whole situation even more irritating.
 

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Hi, you are not alone - I do not understand that someone from GM shop instructors are not on this forum. The problem is far too frequent and tooooo old for them not to know more about it. If they do they do not deserve our patronage.

I have a start booster in the trunk hooked up to the tail light circuit so that it is always fully charged. Twice I needed it because the same problem came up. The car did not start. As if the battery was low, although it was not. Then I hooked up the booster and the car started up without any problem. My booster has only an 18 amphour battery - very small compared with the car battery. The weather was both time very mild and dry. The idea with the booster in the trunk cam after a police officer used his booster when I got stuck at 16 degree F on the highway. There is no problem with the battery although 4 years old. Even in cold temperatures it cranks very powerfully.

My car is a 2010 basic Impala with 82K miles and the basic 3.5 l engine. Yes, I did change the gas pedal and I am thinking of changing the ignition switch. However, I would like to read if other people had found the real problem. There are tooooo many late model Impalas on the raod with the same problem. Being an automotive mechanic and engineer I will not simply run to the dealer and try this or that. My Bank account is small enough.
 

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Discussion Starter #4
I take it you have been left stranded. When my Impala does this, it has in the past always started after a bit. I have never jumped it or anything...just fiddled with the ignition until it finally starts. That's why I had my brother change out the switch....but that wasn't it.

What's with changing the gas pedal? Was it going into low power mode? I wouldn't think that would have much to do with a no crank....

Like you, I don't want to take it to a dealer either. I can throw parts at it just as easily as they can. I'm just getting tired of doing it as well.
 

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Cranking is not directly handled by the ignition switch. One of the electronic modules tells the starter to go.
Corrosion on the High Amp battery connections or one of the ground stud stacks in the engine compartment or passenger cabin?
Corroded relay and fuse panel contacts???

Just throwing this out there.
I might start by cleaning up the ground and hot connections off the battery and hitting them with creeping spray grease like Wurth HHS or Fluid Film. This includes the main power connections to the Fuse and Relay center... these are the ones that feed the control modules that actually handle cranking.
Remove and clean the fuses and try to carefully clean the terminal connections then hit them with spray grease paying close attention to anything labeled ECM TCM or BCM or anything similar.
There are probably several ground stacks in the engine compartment. Clean them and grease them. Then move on to cleaning up any floor level ground stacks in the cabin. I haven't had the carpet out of the Impala but My VW has several at foot level under the side kick panels. They cause all kinds of weird headaches.

The other issue could be the anti-theft system but it should complain in the DIC and or light up one of the hieroglyphs on the cluster...
 

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Discussion Starter #6
Pretty sure anti theft isn't an issue due to the problem occurring with both sets of keys and no security light issues or anything.

Lesson learned on the ignition switch but at least it was only a 20.00 part.

The problem has seemed to worsen after pulling the new battery out and cleaning the connections. When removing the battery on the SS you have to loosen and move the relay/fuse box which leads me to believe that you are onto something with connections there. I may have moved something when removing the battery. Will disassemble and check that first. Thanks for the advice hatzie.
 

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Here is a diagram that may help troubleshooting.
http://www.ricksfreeautorepairadvice.com/wp-content/uploads/2012/07/GM STarting system.pdf

At this point if you pretty sure anti-theft isn't a issue, verify Run/Crank relay energized and then check the PNP switch voltage out to the start relay. PNP switches have been known to be intermittent. If voltage at coil of start relay than it will energize when PCM commands.

Regarding cleaning connections, look at the article on this forum about cleaning connectors to BCM.
 

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Discussion Starter #8
Really appreciate your advice cj1. If I don't see any problems at the fuse/relay box under the hood I will look into your suggestions. My problem is, I can't test anything due to the fact that it won't fail long enough. It will start before I can test anything and that's where the frustration comes. Can't stand driving a car around that can just randomly fail/leave me stranded possibly.
 

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There are a few test that you can make such as start in the neutral position, if it always cranks then the PNP P contact is suspect.

If it continues intermit than you could use a small led as a test light. Mount it so you can see it from the driver position and temp wire it to selected test points. This way you would have a visual indicator and know where you are losing crank circuit voltage.
 

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Discussion Starter #12
It was the under hood fuse block. Bought a new one with all new fuses and relays from dealer for 125.00 and installed it in ten minutes. No problems for months now.
 

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That's great to hear!

I was going to ask if when it wont start with the key, will it start if you use the remote start.

I'm not sure, but I think the SS come with that standard.
 

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Awesome. Thanks for the AAR. It helps other folks who might have the same issue.
 

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tjr1973
Old post , new problem.
The fuse block R&R fixed my intermittent no crank also. There are 10 PCB relays that are found only by taking apart the fuse block, soldered and "non-serviceable" relays. I don't know how you figured the fix but thanks much!
 

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Are you sure there are relays and PCB inside?

The only pictures I've seen of disassembled recent GM fuse block look similar to Telcom punchdown block terminals made of copper with roughly 14ga solid copper wires snaking around to connect the punchdown terminals.

The problem with these is the fuse panel is in the engine compartment so you get vibration and moisture. Those cause the punchdowns loosen up over time allowing moisture and road salt/dirt that causes corrosion at the connection points. The solid copper wires can break off too.

If you can track down which connections are intermittent you can solder them with real 60:40 Pb:Sn electronics grade solder.

This is a Trailblazer fuse panel. I believe the Impala is similar.
GM Fuse Panel.JPG
 

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I'm not sure how to post a picture.
10 PCB relays for sure, 9ea P3CNO12W1 and 1ea 742-355-22. Next to each relay is a surface mount resistor marked "122"
 

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The board looks fine, no corrosion, cold solder joints or bad tracks. It doesn’t pop or creak if the board is flexed.
My wipers were also parking to high and the new fuse box also fixed that. One of the PCB relays is for the wipers.
Thanks again tjr1973
 

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As stated the relays are PCB Relay logic and non service. If something goes wrong past a inner box trace it can be replaced. At wrecking yard at times you can buy the part of the box that's bad. One on here said the part in their area was only 6 bucks.

Sent from my VS880 using Tapatalk
 
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