No spark, but fuses, plugs, and coils are fine, code U2129-00?

2007 CHEVROLET COBALT
234,000 MILES • 2.2L • 4 CYL • 2WD • MANUAL
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SHERLOCKTHC
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I was driving, then the engine shut off. It will crank but no spark. I couldn't jump start it, but I saw the rpms moving. I checked the fuses and tried a few tricks but no luck. After I had it towed, the tow driver left the lights on and drained the brand-new battery. I charged it but my bidirectional scanner only reads a U2129-00 code now. I've had a lot of work done lately to pass inspections. I was trying to fix a P0171 code the day this happened. It was running fine, i took off the throttle body to check for leaks. I put it back on, drove only 3 blocks away and it shut off. The scanner seems to communicate with everything just fine. Upon inspection i discovered oil had leaked down the wire bundle into the ECU plug and elsewhere. I cleaned it all up but still no luck. The car is mechanically sound, i just put a ton of money into it. I've done some random troubleshooting but need help from square one. I'm worried it's a bad wire somewhere but don't know how to check or where to start. Please help bring it back to life!
Mar 23, 2023 at 5:50 PM
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BORIS K
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Hello,

U2129 lost communication with RFA- remote function actuator.
This fault would not cause any non-starting situations.

Do you have communication with the ECM (Engine Control Module)?
If so, next check live data using your scan tool. As it is bi-directional it should be capable of displaying RPM signal. This signal is important for the spark and injectors to be switched by the ECM.

At the ignition coils check
Pin A, black wire ground
Pin D, pink/black wire 12V

You can check this by using a voltmeter or test light.

How to use voltmeter:
https://www.2carpros.com/articles/how-to-use-a-voltmeter

How to user test light:
https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester


A good video how to test spark:
https://youtu.be/1zQQy9noYQ0

Hope this helps.

Cheers, Boris
Mar 24, 2023 at 10:19 AM
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SHERLOCKTHC
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Thank you for your reply! I do have communication with the ECM. It is raining hard right now so I can't test anything yet. I'll reply as soon as I can test.
Mar 24, 2023 at 4:47 PM
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SHERLOCKTHC
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I do not have power to the ignition coils. What should I check next?
Mar 25, 2023 at 9:53 AM
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BORIS K
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Hello,

As you have no power to ignition coils, pin D pink/black wire, I would suggest first checking INJ fuse45(10A) in the under-hood fuse block, next to left strut tower.
See image below.

This fuse supplies 12V to all 4 ignition coils and to all four fuel injectors on pin 1, pink wire.

A good link:
https://fuse-box.info/chevrolet/chevrolet-cobalt-2005-2010-fuses-and-relay

How to check a fuse:
https://www.2carpros.com/articles/how-to-check-a-car-fuse

Cheers, Boris
Mar 27, 2023 at 12:55 AM
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SHERLOCKTHC
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That fuse is good. All fuses are good.
Mar 27, 2023 at 4:29 AM
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BORIS K
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Hello,

Have you checked if the injectors are getting 12V on pin 1, pink wire?
If they are then this could point to a possible wiring issue between the fuse block and the ignition coils.

See image below of engine fuse block showing fuse INJ45.

How to test wiring:
https://www.2carpros.com/articles/how-to-check-wiring

Cheers, Boris
Mar 28, 2023 at 9:18 AM
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SHERLOCKTHC
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I'm having trouble getting the connector off to check the pin. Any tips?
Mar 30, 2023 at 5:46 PM
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BORIS K
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Hello,

There is a light blue/grey clip-on top of the injector connector which needs to be levered up.
Then you will be able to remove the connector from the injector.

See image below.

Cheers, Boris
Mar 31, 2023 at 7:07 AM
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SHERLOCKTHC
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How much voltage should the coils read? When I have the key in the on position, I have power to the coils but it's a low voltage. Yet when I crank, I don't get a spark. Any idea why?
Apr 13, 2023 at 5:53 PM
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BORIS K
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Hello,

You should measure battery voltage, 12V, at each ignition coil on pin D, pink/black wire.
This voltage should be the same as measured on each fuel injector on pin 1, pink wire.
Please ensure that you have a good ground when measuring the voltage.

Cheers, Boris
Apr 14, 2023 at 6:55 AM
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SHERLOCKTHC
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My multimeter is reading 0.67v on pin D on the coil. Battery is reading 12v so that's fine. What could cause that difference?
Apr 14, 2023 at 4:13 PM
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JACOBANDNICKOLAS
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Hi,

I noticed it has been a couple of days since we have been in contact. Have you been able to make any progress? We are interested in knowing.

Also, as Boris said, you should have battery voltage at the coils. If you are getting0.67v, either you have a broken wire, shorted wire, poor electrical connection at the power supply, or even a failing splice.

Let us know what we can do to help.

Take care,

Joe
Apr 16, 2023 at 6:45 PM
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SHERLOCKTHC
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Apologies, I couldn't do much work, my area was hit with storms. I found a melted wire resting on a coolant line. I don't believe its a power wire, but I will send pictures and make the repair ASAP. I still need to check voltage at the fuel injectors, I'm still having trouble removing the connectors.
Apr 17, 2023 at 7:22 AM
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BORIS K
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Hello,

It is important to check the voltage on the pink wire at an injector. This would confirm if the output side at the engine fuse block from fuse INJ45 is intact.
Also measure that you get battery voltage at this fuse.

Please send us that picture of the melted wire.

Cheers, Boris
Apr 17, 2023 at 7:43 AM
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SHERLOCKTHC
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This is the burnt wire and the line it was resting on. I'm currently working on it.
Apr 17, 2023 at 4:15 PM
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SHERLOCKTHC
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I repaired the wire but there was no improvement. When I unplug each coil, the voltage goes up. When I unplug 3 coils, the 4th coil reads 2.8v. Any idea what could cause this and where to start looking?
Apr 17, 2023 at 6:41 PM
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SHERLOCKTHC
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Any thoughts on my last reply?
Apr 20, 2023 at 6:52 AM
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BORIS K
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Hello,

Have you managed to check the voltage at the injectors on pin 1, pink wire?
This would serve as a check for the 12v supply from fuse INJ45.
If the supply at the injectors is 12V it would mean that the output at the engine fuse block from fuse INJ45 is intact, and you are looking at a possible wiring issue to the coil pack on the pink/black wire.

Cheers, Boris
Apr 20, 2023 at 9:16 AM
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SHERLOCKTHC
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I'll remove the fuel rail tonight to test the injectors. I still can't remove the connectors from the injectors, I can't figure out how.
Apr 21, 2023 at 4:54 AM
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BORIS K
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Hello,

As previously shown, you will need to push up the light blue clip-on top of the injector connector. No need to remove the fuel rail.

See image at below.

Cheers, Boris
Apr 21, 2023 at 7:01 AM
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SHERLOCKTHC
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Mine is a green clip and looks different. I'll upload a picture this evening. I can't find any videos or pictures that have clips like mine.
Apr 21, 2023 at 8:14 AM
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BORIS K
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Hello,

I found information for the green clip injector connector.
You will need push down on the connector, squeeze the green tab, and pull connector off injector.

See image below.

A video, it shows removal just after halfway through:
https://youtu.be/CBBCVUcqRfI

Cheers, Boris
Apr 21, 2023 at 9:23 AM