ECM codes: U0101, U0073 and U0100?

JAKNIYAH

MEMBER
2014 CHEVROLET MALIBU
2.0L
4 CYL
2WD
AUTOMATIC
130,032 MILES

Recently got my engine harness wires fixed, made sure the gounding was in good condition. Car is giving out codes: u0101, u0073 and u0100. Is it possible for the ecm to be bad, and giving out them codes? And if the ecm is bad, where can I get a new one reprogrammed at?

Thursday, December 18th, 2025 AT 1:28 PM

4 Replies

JAKNIYAH

MEMBER
39 POSTS

Also, will a no-good alternator have/send out the same codes: U0101, u0073 and u0100?

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Thursday, December 18th, 2025 AT 4:26 PM

KEN L

MASTER CERTIFIED MECHANIC
54,852 POSTS

If the battery is charged you should be okay for a short time but yes the alternator need to charge to keep the voltage above 12 volts.

U0073 - Control Module Communication Bus “A” Off
U0100 - Lost Communication With ECM/PCM
U0101 - Lost Communication With TCM

I would check all fuses with the key on using a test light

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

I would double check the wiring harness repair because these codes come up when the wiring is not correct. Please go over this guide and get back to us. Do you need the wiring diagrams and a guide on how to test the connections?

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Friday, December 19th, 2025 AT 10:52 AM

JAKNIYAH

MEMBER
39 POSTS

A guide on how to test the connections would be great.

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Friday, December 19th, 2025 AT 11:46 AM

KEN L

MASTER CERTIFIED MECHANIC
54,852 POSTS

Sure here is a guide on howe to test the connections.

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

Here is the wiring diagrams you need to help. You will need many so I would get the Alldata DIY sub for a couple of bucks for your car.

https://www.alldata.com/diy-us/en

Let us know how it goes.

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Saturday, December 20th, 2025 AT 11:34 AM