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Car wont start, security light stays on and will not reset.

Customer Question
After fooling with it for...
Car wont start, security light stays on and will not reset. After fooling with it for several days the bcm has started intermittently clicking 2 or 3 times every 20 seconds or so. And the doors keep trying to unlock. The same time the bcm started clicking the car started acting like the battery is died by locking the key in the ignition and all dash lights went out. I know for a fact the battery is good. Clicking happens with key in ignition and without. Clicking stops if i remove the lower right connector from the bcm. But it went from a no start with power steering and low fuel message, to a security lockout, to unresponsive and bcm clicking
Submitted: 3 months ago.Category: Chevy
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Answered in 2 minutes by:
3/22/2018
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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It sounds like the battery is low. Battery may very well be "good" but this sure sounds like a discharged battery, causing all of the clicking and whatnot. Computer hate low voltage, they will usually start cycling relays and things like that when the voltage drops.

I would start by putting a battery charger or jumper cables on this, and measuring system voltage to make sure it's up where it belongs. We still need to do other things, too, but the car won't do anything without proper battery voltage.

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Customer reply replied 3 months ago
You have helped me with this issue several times. Just been waiting 2 days on a response for the last ticket. I just pulled the battery off of a charger, it was good when i hooked it up, still reading good
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Ah, I'm sorry! I did not get notification that you had responded.

Bring me up to speed on this, refresh my memory. I don't recall the steps we took.

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Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Looks like you were trying to clarify one of the grounds to the ECM, did you have no ground at pin 73 connector C2? You were on C1 at the end of the last conversation, I just reviewed it.

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Customer reply replied 3 months ago
First it was a no start with power steering notification and low fuel light. I rented a relay test kit, saw nothing wrong. Then it added a security lockout that will not clear/reset. Then you gave me a pinout for the ecm (which was wrong, not a single pin matched your pinout). While troubleshooting today all the dash lights went out, except for the security light. Now the bcm is clicking and the security light flashes when the bcm clicks. It stops if i remove the lower right connector
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Removing power from the BCM will stop it from doing anything at all, so it's not surprising that it stops clicking when you unplug it.

You have a 2.2L engine in this, yes?

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Customer reply replied 3 months ago
Both connectors to the ecm had 73 pins. None of the pins in your pinout matched my readings. C2 has a good ground on 73. C1 the light was a litte dimmer on pin 73
Customer reply replied 3 months ago
The motor doesnt say the displacement anywhere on it that i can find
Customer reply replied 3 months ago
I gave you the vin and you said the motor was l61 i believe
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Both connectors can't have 73 pins. Any ECM that goes in this car has one connector with 73 pins, and one with 56 pins.

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Customer reply replied 3 months ago
The pinout you gave me was saying one connector had 72 pins, the other had 73. Both of mine had 73. Their identical except one is grey and the other is black
Customer reply replied 3 months ago
Unless it was 73 and 56. But both of mine are 73
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

OK, there's the problem. This is a 2008 Cobalt, not a 2006. I didn't check the year on the vin you gave me last time, only the engine designator. I assumed you had the correct year.

Let's start over on this.

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Customer reply replied 3 months ago
Wow, i feel dumb, i guess ill never ask my gf to check the year for me again
Customer reply replied 3 months ago
When the bcm clicks the fuse box under the hood clicks and the turn signals briefly flash
Customer reply replied 3 months ago
The car does not respond now to the key, the dash doesnt light up, no electronics respond. Jusy the security light stays on, and flashes with the clicking
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Can you put a multimeter to that battery and verify the voltage at the battery posts?

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Customer reply replied 3 months ago
Now im wondering if my battery charger is bad too...i dont have a multimeter. But jumping the car the other day didnt help
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

I just want to make sure there's power to these circuits, there are few things worse than checking a whole lot of circuits and things, only to find that your battery was dead the whole time.

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Customer reply replied 3 months ago
Im getting scared thats the case. It was fine last i checked, and jumping didnt help any. But it looks like it is dying now. Just like my daylight
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Let's hit the reset button on this. Work on getting sufficient battery power to this, we'll start fresh tomorrow and revisit all of these things, because the differences between 2006 and 2008 are important enough that we need to cover those bases again.

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Customer reply replied 3 months ago
If the battery was the issue, wouldnt jumping the vehicle have corrected the problem? I couldnt get the security system to clear no matter what i did, even when it was hooked to a running vehicle
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

I don't think low voltage is the only problem, I just think it's the problem you're having with all of the clicking of relays and other fussing. Before we start checking any circuits, we have to make sure our battery is up to speed, or we'll end up pulling our hair out trying to figure out why nothing works, only to find out 7 hours later that the battery was dead the whole time and none of the test results mean anything.

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Customer reply replied 3 months ago
Ok, i has the battery tested and charged. Battery was good, but it was dead. I guess about 20+ hours of troubleshooting over 5 days with key in on position was its limit. Im trying the security reset/relearn now. Im just starting the third 15 min wait for the relearn/reset
Customer reply replied 3 months ago
The security light does not go off after 10-12 min like most have said it should. But i know the full relearn takes 3 cycles
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Did you get anywhere with the security on this?

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Customer reply replied 3 months ago
I did not. The dealership said the security will not stop the engine from cranking, it will jusy prevent it from starting. They said it could possibly be the whole security and/or computer system needs to be reset. Bring it to them and pay $100 for them to look at it and maybe they will find something. I told them i cannot afford stealership maintenance.
Customer reply replied 3 months ago
I did not. The dealership said the security will not stop the engine from cranking, it will jusy prevent it from starting. They said it could possibly be the whole security and/or computer system needs to be reset. Bring it to them and pay $100 for them to look at it and maybe they will find something. I told them i cannot afford stealership maintenance. I want to find a way to remove chevys poor excuse for secuity system. Or to bypass it, but i fear it is too integrated
Customer reply replied 3 months ago
I apologise for the duplicate posts, it doesnt show that it posted on my end anymore until i reload the page
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Bypassing is not reliable. Many have tried, many have failed.

I've been multitasking and can't remember our previous conversation. What do you have for a scan tool?

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Customer reply replied 3 months ago
Im wondering about just hooking a fuse, hardwire, and a switch to the fuel pump, and starter to try to bypass the security system
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

You can't do it. If the ECM doesn't get the password, it shuts off the fuel injectors.

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Customer reply replied 3 months ago
It is one of those cheap elm327 wifi obd scanners
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

OK. So it only communicates with the engine computer, not anything else, right?

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Customer reply replied 3 months ago
It is supposed to link with a phone app that can check all the vehicle information. If i read its description right
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

I think those setups only get engine codes, though. And do you have communication with the car at all?

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Customer reply replied 3 months ago
It read battery voltage, and the trouble code u0100 last time i checked
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

You are handicapped by your lack of a good scan tool. I know this isn't what you do for a living, you shouldn't invest in a scan tool that costs several thousand dollars.

I am looking through a historical database of repairs, and I can look these up by symptom and by trouble code. I look up U0100, and I see a long list of ECM replacements. A few other things sprinkled in there, too, but ECM's seem to be the thing.

A new ECM requires programming with dealer-level equipment, so you may want to consider giving them the $100 to diagnose this, and maybe paying them to repair it. If it needs an ECM, you'd probably be looking at $800 parts and labor by the time they're done cleaning your wallet out.

Where do you live, what part of the country?

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Customer reply replied 3 months ago
South Mississippi
Customer reply replied 3 months ago
Do you think this could be cause by a bad ground to the ECM? When i was checking the pins before pin 73, which is a ground on both ecm connectors. One of them was good, the other the test light was only about half as bright
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Mm. I don't have any friends down there that could help you, either.

You can put a used ECM in it if you can find exactly the same car with the same engine. You'll have to do the security relearn, you know how to do that, yes? And you can get a used ECM for $100 or so (I see a bunch of them in Alabama for $100 on car-part.com).

If I were in your shoes and was ready to make an educated guess, I'd probably go get one of those ECM's and just plug and play it. Or plug and pray might be more appropriate. :-) It's as educated a guess I can make with the limited amount of diagnostic data we have to work with.

Please take a moment to rate my answers by clicking on the stars at the top of the page, that's how I get compensated. If you need more help, just let me know, I am happy to follow up.

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Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Pin 3, 19, and 20 on X1 connector should have power with key on. The only ECM ground is at pin 73 on connector X2. Pin 73 on X1 is actually a power circuit too, but only when the ECM closes the powertrain relay, so you won't measure any voltage here when you are testing.

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Customer reply replied 3 months ago
I read a ground to both connectors pin 73. Just one of them was weak. I forget which connector. I have it written down at home, i will be back there in 15 min
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

Probably the X1, since it doesn't get power until the relay closes, it's probably finding a weak ground through the relay. Electricity does that, it will find a ground, but it doesn't mean anything in this case. The computer is looking for power on that circuit when the powertrain relay closes.

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Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

I'm going to be traveling home in about an hour, so I'll be away from my desk for a bit, but I'll be around this evening to help you with it, if necessary.

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Customer reply replied 3 months ago
Ok, thank you
Chevy Mechanic: Jerry Newton, Chevy Technician replied 3 months ago

I am back at my desk for a few hours if you want anything out of me.

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