No crank, No start, not even a click. 2008 Aura 2.4
 

As the title says... 2008 Saturn Aura, Ecotec Le5 Engine... The code reader reads no comm with the ECU u0100 I think. I pulled the starter and tested it, and it works. I tried to bypass the ECU through the starter relay port, and starter cranks to no avail... I checked the battery, tried jumping, tried jumping while bypassing, nada... I took the cover off the ECU to see if it looked fried, it looked fine but am unsure how to test it. Tested every fuse/relay... HELP. I'm sorry if you're seeing this post everywhere... One day it just stopped cranking in my driveway

I have been suggested to replace all the grounds, which seems daunting and tedious. I was also told that I couldn't just clean the contact of the ground and that I need to replace the entire wire... Seems complicated, never done that. I have also been told that it is likey a dead ecu as this issue is common. I am willing to try anything, thank you for the help in advice, and thank you for your time reading this.

Does your instrument panel light up when you turn the key on? Do lights, wipers, blower motor, etc. work? I doubt you have a ground issue if everything works but the starter circuit. Have you run the gear selector through park and neutral when trying to crank the engine?

(And for the sake of old eyes, please post using black text on white. No points for creativity.)

Do you have any tools. DVOM? Why did you try to read codes? What happened just before this. A little history will help.

YES to everything... I just checked all of the grounds today anyway. A little green corrosion here and there but it came off easy...

Yes, I have a multimeter... A few days earlier it didn't start on the first try but it did on the second, I thought this indicated a starter issue or battery issue but I tested both, again as I mentioned.

Why did you look for codes? Because it didn't start? What happens when it don't. No crank? Need to know where we are at.

How did you test the battery?
Need to pull it and take it to AutoZone or similar and have them load test it.

Can also put a voltmeter across it, DC, and monitor the voltage as a friend turns the key to crank. If it drops much below 11.5, your battery is likely done.

Sometimes the positive cable under the hood becomes corroded internally and loses continuity to the starter. There is also usually an ignition wire that when ignition is turned energizes a starter relay which connects the battery up to the starter.

Plenty of places for faults. Not being able to read codes is usually a fuse issue but not always. Leave the ECU out of the discussion until all other avenues have been addressed.

Try checking for continuity and resistance between the positive battery terminal and the positive battery lead and where it attaches to the starter. Some go straight through, some are branched..

Measure the resistance between your negative battery terminal and an unpainted frame ground

Since you are getting no clicks at the starter, check that the wire from the ignition relay that enables the starter is actually being energized.

You are going to need someone that has a real scanner to see what works and what doesn’t work. If all the computers work except the ecm then it probably needs an ecm. You are just guessing without proper diagnostic equipment. My 2002 is fairly simple just a handful of computers, by 2022 the trucks I work on have 20+ computers talking on three different networks.

I disagree, I would recommend this step but it was not necessary. seeing that the ECU wasn't communicating through the DTC to the scanner is inconclusive. I had to eliminate voltage/continuity tests through the pins on the connector for the ECU, along with the ignition switch, transmission range switch, can bus, battery, starter, etc. To ensure that it was not a wiring issue before buying a new ECU just based on a DTC reading.

https://charm.li/Saturn/2008/Aura%20...trol%20Module/
The diagrams that I used to test the pins are here ^ labeled LE5