2008 Aura No crank
 

Hey guys/gals Working on the wife's car. Radiator leaked, so I replaced it. Started right up with no issues. Wife wants to talk, so I shut it off. After her talk I get an intermittent no crank. When it will crank I get the full 12.2 volts to the starter. When it wont crank, I can hear/feel the run/crank relay click, but not the starter relay. After looking at a few things, now when I plug in my scanner, it shows no communication from the ECM. From what I see, when you turn to crank it sends a signal to the BCM, then a request to the ECM, then to the run/crank relay, then to the starter relay. The small bits of wiring diagrams i can find says that the info from the two relays is inside the fuse block, which sounds weird, but weirder things happen. remove the underhood fuse block to check for corroded terminals, heated and burnt plastic block, etc. Nothing. Recheck and still not getting any power to the starter. Hmmmm? any ideas? Now when I removed the radiator for replacement, I made the mistake of pulling the fan assembly, not realizing that the radiator came out from the front side of the core support, not the rear. I did break a wire doing this, but I repaired it properly, including heat shrink tubing. I inspected all the other wires and found no issues. The wire harness that is in question does NOT contain the purple starter solenoid wire.....
2.4 4 cylinder

What engine?
You can find it in here.
https://charm.li/Saturn/2008/

UPDATE: Now it starts almost every try, but my scanner still reads "unable to establish communications, be sure the key is in the run position", and the check engine light is on, but I cant read the code due to no communications. The dash says "power steering", but the power steering seems to be working just fine. Also the atmospheric temp is "---" and the tire pressures are "---". Just weird

Pull the fuse block again.
WIth battery disconnected, clean w electrical contact cleaner. Both the panel and the block terminals.
It sounds like you have lost either power or ground somewhere.
If you disassembled the fuse box and put it back together with different results, I'm thinking it's a poor connection or connections between the panel and the block. You also may have disturbed a ground at the block.

Do you have a wiring diagram?
What engine is this?
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When the radiator leaked, where did the coolant land? Basically I'm asking if any coolant, and or any distilled water, could have found its way into the fuse box or in contact with any of the wiring harnesses leading to or exiting the fuse box.

Sorry, I editied the post to say 2.4, 4 cylinder engine. Radiator replace because the original hose clamp was broken. Ive never seen this before, but the original spring type clamp, one end rotted off and broke, causing a very slow leak at the passenger side of the radiator. Very good thought, but no coolant touched eighter the ECM or the TCM. Coolant on the passenger side was too far away from there, and coolant was drained via the radiator hose by radiator hose removal on the d rivers side, and went straight down, not onto the ECM or TCM. I do not have a wiring diagram, but that would be helpful. Very helpful. If you know where I could get one, that would be great. When I removed and inspected the under hood fuse block, I also moved, but did not unplug the ECM, to look for wire issues. Yes, it could be fuse block issues, but could also be wires to/from the ECM. Engine is still starting ok, but I do not trust it since I havent actually found an issue. Check engine light is on, with "failure to establish communications" comes up on my scan tool. Im thinking Im going to remove all the conduit from the wiring harness that I may have harmed when removing the fan assembly, for detailed inspection.
To reiderate the issues: intermittent no crank/start, no comunications from the ECM, check engine light is on, and dash shows missing info from tire pressure and atmospheric temp. To me this sounds like ECM and BCM issues.
Any help or thoughts are appreciated.

From a quick perusal of the electrical schematics, the one thing that all of your car's misbehavior has in common is a communications network. While not surprising, the TPMS, power steering, instrument cluster temperature display/outside air temperature sensor, and the OBD2 port all rely on fully intact communications lines in order to communicate to the ECM and BCM.

I suspect that in moving the ECM, you may have disturbed one of the connections. Even though the pins are covered nominally, you can still get a thin layer of corrosion building up between the pin and its socket in the connector, and a little bump here or there can lead to an intermittent connection. After 16 years of sitting in place then being jostled, I don't think it's an unreasonable place to start.

I would, after disconnecting the battery, carefully remove each of the ECM connectors and inspect the pins and the sockets for corrosion.

Try sweeping the contacts by putting the connector on and then removing it. Repeat about six times. Be very careful that you do not force anything. If you are forcing something you are likely bending a pin and you really don't want to go there. Sweeping the contacts may be enough to restore full connectivity.

Electrical contact cleaner from a reputable source can be used to dissolve any buildup. Just refrain from rinsing skuzz from some of the pins onto all the rest of the pins. Hold it so the pins are running horizontally. Inspect the connector as well. If there is not any significant buildup in the connector, a quick spritz is fine. Just don't soak them. Also ensure that all of the sockets are properly sprung and ready to receive the pins. If any are bent out of the way and unlike the rest, you may need to address that as it may be part of the reason for intermittent contact.

So that's where I would start.

The wiring diagram can be found at

https://charm.li/Saturn/2008/Aura%20...d%20Diagnosis/

I believe if you find the physical location in the wiring where the TPMS, power steering, diagnostic port, and instrument cluster temperature display / outside temperature sensor connect into the communications network, you can narrow this down as being located in a certain portion of the wiring.

Remember the communications network itself is a continuous entity, so if there is an open circuit condition on the network, it depends where it is as to what it will affect. Different modules may act in different ways when they are not happy.

If you cannot restore the communications network, you will probably need to take it to someone with the automotive network troubleshooting tools to diagnose and address.

All very good stuff. I wont be able to look at it until the weekend.
I had a thought about a bad ground. Specifically G109. The wire I damaged went to a multi ground to the block behind the alternator. Im not sure what it went to, but maybe I damaged more than I thought. I peeled the conduit off most of the wiring in that area and repaired a possible large ground wire there. I didnt think that it was badly damaged, but it felt funky, so why not repair it? No change. Although, how I damaged the small ground wire makes me wonder if I pulled on the other grounds in that area. I had been rough on all the wires there when I reinstalled the cooling fan assembly. I will for sure look at all those wires. I had seen someone on YouTube talking abut a very similar issue, where the starter relay wasnt clicking, and resulting in a no crank issue. he found no ground to the starter relay did not have ground to the effected side of the relay(not the side that gets grounded from the EVM/BCM) . I will check for ground or no ground there. He introduced a good ground and it started right up. As you can probably tell, I do have a grasp on some electrical stuff, but I'm not great at it. I appreciate you realizing that im not completely ignorant, but I may need some help on locations of things like grounds and such.
Thank you so much!

Take the battery out and take it to your local auto parts store and get it load tested. 12.2 is kind of on the low side for starting the car. I'd start with that if it was my car.

I see your info and it is apreciated. However, if the issue was a slow crank, or even a clunk from the starter, I would have a very different approach than what I already have. I actually found the issue being a severely corroded and broken ground. I think it was either G107 or G109. Thanks for the input.

Thanks everyone, I found the issue. It was a severely corroded and partially broken common ground, which I beleive is G109. Left side of the engine, under the intake manifold, behind the alternator, with a total of 5 ground wires. Im actually surprised that there weren't more issues since the ground was such poor shape. Several splices, and repairs should have it up and running soon. THANKS again!